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  1. For those interested, please find a new article under the "History and Reference" section, below. Aloha, Robert
  2. Understanding the Open Rear Bulkhead Design Features Essential for the Application of Primer Coatings Using Anodic Electrophoretic Deposition on The Early BMW Neue Klasse Sedans and the BMW 02 Series This article offers some explanations for specific design features of the 1960s and 1970s BMW Neue Klasse four-door sedans and 02 Series sedans. The features most closely scrutinized include the open design of the rear bulkheads in early Neue Klasse (NK) cars, triangular cutout holes in solid bulkheads of the early 1600-2 02 Series sedans, and various bulkhead and box metal holes in the trunk areas of all NK and 02 Series sedans. The article seeks to explain the design features that enhance the anodic electrodeposition coating process. The author’s comments are specific to the four-door BMW Neue Klasse Sedans, and the BMW 02 Series which are defined as the BMW’s two-door sedans, including the 1600-2, 1602, 1600ti, 2002, 2002ti, 2002tii, 1802, and 1502 models. Authors Robert P. Smith, @BritshIron BMW 2002 FAQ, USA Nelson K. Akafuah, Ph.D., Univ. of Kentucky Adnan Darwish Ahmad, Univ. of Kentucky Overview During the 1950s and into the early 1960s, entire car bodies were being immersed in vats of primer paint along the assembly line. At first, solvent-based primers were used, which caused environmental hazards and even explosions. For a relatively brief period in the history of automotive primer coating, a water-based primer was used during vat dipping. However, the process still relied on simple gravity to get the primer coated on all parts of the automobile body shell. By the mid-1960s, BMW was using a type of primer coating which utilized electrophoresis in an electrochemical process that would soon be the standard for automotive protective coatings. In the early years of the BMW Neue Klasse cars, the first years of the 02 Series 1600-2 and 1600ti, and the entire remainder of the 02 Series through 1977—these sedans had some holes and openings in the rear bulkhead (the metal partition behind the rear seat back separating the passenger cabin from the trunk space) as well as holes in other parts of the trunk space. There are very few written documents which explain the purposes of these factory design features, and (thus far) no definitive oral history. This article explores the various rear bulkhead types in these early cars. It explains how these openings enhance what BMW called at the time “Electrophoretic immersion bath” or simply “Electrophoresis.” The process is called by many other names, including electro-coating, electro-painting, electrodeposition, and electrophoretic deposition. Electrophoretic deposition (EPD) is the process where specially formulated primer paint is applied after the phosphate pretreatment of the metal substrate to promote long term corrosion resistance. For the anodic EPD process, the metal body shell carries a positive charge, and a uniquely formulated primer resin carries a negative charge. Thus small paint particles are attracted under electrical influence to a positively charged workpiece (the vehicle). The paint forms an insulating film on the metal, which provides a chemical and physical barrier to prevent corrosion. This paint insulation spreads uniformly to otherwise inaccessible areas of the body, and the distance of such spread is known as “throw power.” Adequate primer coating is highly dependent on open pathways for dispersal of pretreatment liquids and primer throughout the body shell, voltage applied to car body and primer, the paint bath temperature, bath non-volatiles, and vehicle duration (immersion time) in the bath. After immersion, time and temperatures in a drying oven are also critical to the process. Assembly Line Pretreatment of the Metal Substrate Before the Electrodeposition Process For optimum protection of the body shell, it imperative to properly prepare the metal surface for the EPD process. The pretreatment allows for a more uniform primer layer. It is chemically driven and in multiple stages, including the following steps: Hot Water Rinsing, Degreasing, Surface Conditioning, and Phosphating Processes. Other critical process parameters are monitored continuously in the pretreatment bath, including the incoming metal quality, water quality, vehicle immersion time, turnover rates, rinse impingement, and surface flow. Adequate liquid filtration is essential throughout the pretreatment stages to maintain excellent corrosion protection and optimal surface quality. The goal of the pretreatment is to have an optimal phosphate crystal structure and coverage on the metal substrate, getting the car ready for electrochemical primer coating. The authors wish to note that these pretreatment steps also require enough adequate openings in the automotive shell so that pretreatment liquids can reach all portions of the body. The Anodic Electrophoretic Deposition Process of the 1960s Anodic EPD technology, introduced in the early 1960s, is an efficient and relatively simple operation with a high degree of automation. The anodic EPD process was subsequently replaced by cathodic technology in the 1970s, the latter which has set new standards in EPD processes and corrosion protection that extends to this day. By 1970, 10% of all vehicles worldwide were electrocoated. By 1990 this had risen to 90% of all vehicles, and today it is by far the most commonly used vehicle coating process (Ansdell, 1999). The liquid primers used in the EPD are often called “electropaints.” Red primers were derived from iron oxide, and grey primers from titanium oxide, mixed with carbon black and yellow iron oxide. In the case of BMW, the company apparently switched from red primer to grey primer sometime around the middle of 1966. Up until 1977, all electropaints used in the automotive industry were of the anodic type, primarily because the resin chemistry was relatively simple, readily available, and adaptable to the needs of the auto industry. In this process, the car was the anode. Figure 1 shows a schematic of the anodic EPD process. The EPD process was reported in great detail by Fettis (Fettis, 1995); a summary is presented here for convenience. A portion of the great success of EDP in the automotive coating process is attributed to throw power. Throw power is a sophisticated yet essential property that defines the ability of an EDP process to deliver primer coating to more remote and harder-to-reach areas. Optimum throw power can depend on a number of technical factors, including pigment volume concentration (which affects film resistance), non-ohmic conductance, rupture voltage, coulomb yield, and neutralizing species type. It is worth mentioning that the typical throw power of the anodic EPD process is about 12-15 cm, while it’s 25-35 cm for the cathodic EPD. The furthest the distance coated and the thickest the film, the better the throw power is. Figure 1 Schematic of the anodic electrodeposition process (Adopted from Fettis 1995) The anodic process had some deficiencies. The two primary weaknesses were phosphate disruption and poor saponification resistance. Note, saponification is a process by which triglycerides are reacted with sodium or potassium hydroxide (lye) to produce glycerol and a fatty acid salt called soap. The best EPD results include resistance to saponification. During the anodic EPD, very high electrical field forces occur, which rupture many of the metal-phosphate bonds (called phosphate disruption). This leads to a weakening of the adhesion of the phosphate coating to the steel substrate. When subsequent paint coats are applied, stresses are set up in the entire paint film, which, when such damage gets to bare metal, tends to cause the entire paint film to curl away from the damage point. In early anodic systems, as soon as corrosion started at any point of damage, the weakened phosphate layer allowed the paint to peel back, exposing more metal, which was chemically clean and very prone to corrosion. This failure was designated ‘scab corrosion.’ This undesirable property was improved by reducing the incidence of rupture of phosphate bonds by merely increasing their number, i.e., modifying phosphate coatings with densely packed, fine phosphate crystals. Such dense phosphate coatings are of low coating weight, and their introduction led to a marked reduction in the incidence of ‘scab corrosion.’ The chemistry of many early anodic primers was characterized by the use of acid resin chemical systems; therefore, poor saponification resistance was inherent in these electropaint primers. As a consequence, the deposited cured primer film (based on acid resins), when exposed to an alkaline environment, will tend to form metal soaps soluble in water. When damage occurs to bare metal, caustic salt will simultaneously attack the steel substrate and the electrocoat film, producing rust and the sodium salt (soap) of the anodic resin. This dissolves the primer coating, leading to a loss of adhesion of the remaining paint film and general corrosion problems (Ansdell, 1999). Electrophoretic Deposition Design Features in BMW Sedans of the Early 1960s Early 1960s BMW sedans (which introduced the now iconic C-pillar “Hofmeister kink”) began with the Neue Klasse (NK) 1500 sedans, introduced in Frankfurt Motor Show in 1961. Figure 2 Neue Klasse BMW of the late Sixties taking a dip in the EPD primer bath. Photo: Schrader (1979) "BMW, A History" These four-door sedans included the NK 1500 (1962-1964), NK 1800 (1963-1968) NK 1600 (1964-1966), and the NK 2000 and variants (1966-1972). Figure 2 shows a later Neue Klasse sedan in the electrophoretic immersion bath. A photo of the rear bulkhead of a 1963 NK 1500 appears below, the green car (Figure 3). Note the two, vertical oval bulkhead cutouts on each end of the partition, and the rather large, more square openings in the center of the bulkhead. The authors believe this open rear bulkhead design helped facilitate dispersal of pretreatment liquids, as well as primer during the vat dipping process. Similarly, the small hole at the top of the wheelhouse arch is likely a “vent and drain” hole that allows the primer-related liquids to enter the box metal, and also promoting a means for air trapped in the box metal to escape. Also, note the vertical, pressed grooves in the sheet metal on either side of the oval cutouts, as well as in the center dividing metal. The oval cutouts have rolled metal edges. All these intricate pressings and punching of the flat metal is done to give the sheet metal the strength and rigidity needed for such an important structural application. It also appears that this bulkhead relies on five separate metal parts to form the skeleton of the bulkhead partition. Finally, BMW installed a trim board on the rear seat back side of the vehicle as a finishing feature. An early Neue Klasse sedan in the assembly line process after final paint is shown in Figure 4. The open design of the rear bulkhead can be clearly seen against the contrast of the trim board. Note the center metal stanchion separating the two largest open areas, and giving some strength to the mid-sections of the bulkhead. Figure 3 Rear bulkhead and wheelhouse of 1963 Neue Klasse 1500. Arrows indicate oval cutouts. The circle at the “vent and drain” box metal hole. Star in large bulkhead opening. Photo courtesy of BMW 2002 FAQ Figure 4 Neue Klasse on Assembly Line. The arrow at center metal divider of bulkhead frame. Photo: BMW Group Archive Sometime in 1964, the rear bulkheads in these NK cars changed from the framed-up cutout design to a solid bulkhead. The trim board was moved outboard of the solid bulkhead, so the trunk had a very finished look. Figure 5 shows a photo of the solid bulkhead with the trim board not yet installed, so you can see a pressed design very similar to what will soon become the familiar rear bulkhead pressing of the 02 Series cars. At the Geneva Auto Show in March 1966, BMW introduced the first of the company’s new 02 Series, the 1600-2. (“2” was to signify two doors, and a way to distinguish this new model from the four-door NK 1600). From the very first 1600-2 in March 1966, as well as early 1600ti cars, there were unique cutouts, die cut from the pressed sheet metal design on either side of the rear bulkhead. These cutout “triangles” remained in the design until approximately the end of November’s production, 1967. Figure 5 Later Neue Klasse Sedan with Solid Rear Bulkhead. Photo: BMW Group Archive After that, the bulkhead returned to the solid form in all 02 Series cars, except for a much smaller hole (25 mm), drilled into the solid triangular pressed bulkhead design that had previously been cut out of the 1600-2 cars. Regarding the cars with triangular cutouts, the factory covered these cutouts with acella film (think translucent plastic sheeting) during final fit and finish procedures. Figure 6 shows the inside trunk of a grey car with the factory acella film installed. Note the black wire and the wiring chase at the top of the wheelhouses, this hole goes through to the cabin of the car. At least one additional hole is present on the box metal forming part of the wheelhouse arch in the trunk of all 02 Series cars, from the first 1966 1600-2 to the last 1502 in 1977. These holes were oval shaped and uncovered (Figure 7). The authors believe BMW designers purposefully included open bulkhead designs in early NK sedans, and the triangular cutouts in early 1600-2 cars, as a way to ensure pretreatment liquids and primer during vat dipping were distributed (as much as possible) throughout the car body. Figure 6 Early1600-2 rear bulkhead with acella film installed. Arrows point to acella film covering triangular cutouts. Photo: Anders Bilidt Figure 7 Oval wheelhouse box metal hole and triangular cutout in a 1967 BMW1600-2. Circle at “vent and drain” box metal oval hole. Arrow points to wire chase penetrating the bulkhead. Star in triangular cutouts that allow for primer distribution and air bubble release during electrophoresis primer immersion. Photo: Robert P. Smith Other holes in box metal components accomplished the same purpose. Drain holes in the spare tire well were similarly intended to provide adequate drainage of primer liquids, similar to the large drains in the cabin floor of the bodies. Holes cut by the factory in the rear package shelf (some call “rear deck, parcel tray, or hat tray”) also allowed for the passage of liquids associated with the primer process, as well as avenues for air bubbles to escape during vat immersion (See Figure 8). These holes in the rear parcel tray were present for the entire production run of the 02 Series, 1966-1977. Figure 8 Factory drilled holes in the parcel shelf of a 1600-2 made in September 1967 helped to disperse liquids associated with the EPD process, and air bubble escape passages during immersion dipping. Photo: Robert P. Smith Such holes, openings, drains, and cutouts provided (1) physical access for all liquids associated with the primer process to flow to all areas of the body, and (2) “vent and drain” opportunities for excess primer products and trapped air to exit the car body during the primer coating process. When electrophoretic immersion was added as part of the primer application process, these various openings became all the more important to assist with throw power requirements of EDP in order to get primer into normally inaccessible areas of the car body, and air bubbles out while the car was being immersed. The authors offer two points of reference that could shed light on the emphasis BMW placed on this relatively new EDP process in marketing the early NK and 02 Series cars. Regarding both the Neue Klasse and 02 Series cars, the YouTube video below depicts the NK/02 Series production line, courtesy of the BMW Group Archive. A full two minutes or more of a 14-minute production documentary is devoted to the electrophoresis process, and how much that process helps the quality of the paint on the finished car. The second point of reference can be found in early BMW 02 sales brochures (Figure 9 and 10), again touting the electrophoretic immersion bath with words like “All the inaccessible corners and edges of the body, outside reach for normal painting, are also covered with anti-corrosive filler.” Note the BMW shown on this brochure is an early 1600-2, with the triangular bulkhead cutouts and covered with red iron oxide primer. The photo and text of this brochure exemplify how BMW can get paint to all the nooks and crannies during the vat dip, demonstrating the throw power of the new EPD primer process at the time. Note the sales brochure in Figure 9 is dated May 1968, but the 1600-2 photo is from an earlier car using red primer. The second brochure (Figure 10) is from August 1968 and features a later 02 Series car in grey primer, with the smaller, 25mm holes in the rear bulkhead. The sales brochure in Figure 10 was captioned "Electrophoresis" Why did these early rear bulkheads finally take on a solid design? For the 02 Series, The Federal Motor Vehicle Safety Standards Act went into effect on January 1, 1968, and mandated solid rear bulkheads as a safety measure to separate the cabin area from the fuel tank on cars. For the Neue Klasse cars, the first impetus to do away with the open rear bulkhead and replace with a solid bulkhead may have been a part of an earlier United Nations agreement which also spoke to fuel safety and cars. Many European countries, including Germany, were signatory to the United Nations Economic Commission for Europe framework, first signed in March 1958. Parts of this agreement, as amended, cover approximately 147 technical regulations on vehicle safety and environmental concerns. Among the subjects covered are mandatory partitions that separate the passenger compartment from the fuel tank, and standards which limit fuel drip into the passenger cabin under crash conditions. Figure 9 A portion of a May 1968 sales brochure touting E-Coating for BMW 1600-2. Photo courtesy of BMW 2002 FAQ Figure 10 Page from a BMW sales brochure from August 1968 showing rear of 02 . Photo courtesy of BMW 2002 FAQ Given that the agreement allows signatory countries to implement the terms of the UN agreement at various times, it may have been that Germany decided to implement the solid barrier separation between the cabin and fuel tank in 1964. In Europe, this rule is often referred to as the ECE 34 Regulations. The USA never signed the above referenced UN agreement, but rather adopted its own vehicle safety standards, as did Canada. The end result was the Federal Motor Vehicle Safety Standards Act, effective January 1, 1968, mandated the solid rear bulkhead to separate the cabin from the fuel tank area (trunk) in a similar fashion to the earlier UN agreement for European cars. All “US spec” or “Federalized” BMW 1600-2 cars, titled as 1968 models and sold mostly through US dealerships such as the Max Hoffman Corporation, were supposed to have solid rear bulkheads. It’s unclear how many BMW 1600-2 cars, made between September and November of 1967, made it to the US as 1968 Federalized cars with the triangular cutouts in the rear bulk-heads. However, it is believed that no US “Federalized” 1600-2 made after November 1967 had the triangular bulkhead cutouts, nor did any 2002, 1802, 1502—no 02 Series car after approximately November 1967. Indeed, the final chapter to this “holes in the rear bulkhead” story goes to BMW 02 Series cars made from December 1967 until the end of production. The authors believe every one of these hundreds of thousands of cars (1502, 1602, 1802, 2002, excepting any “Specials” like the Baur cars) had holes drilled in the very same rear bulkhead panels that had been removed in the early 1600-2 cars. In other words, just because some regulations called for diminishment of early, larger “vent and drainage “ triangular openings for primer dispersion and air bubble escape, it looks like BMW did not give up on the notion of having some way to disperse primer to remote areas of the car’s shell, as well as have holes to allow air bubbles to escape during the EPD immersion dipping process. For paint dispersion, it looks like the holes are positioned to make sure paint gets in the inaccessible cable chases at the top of the wheelhouses (where wheelhouse meets bulkhead) and along welding points. These smaller holes in the bulk-head may also have served to supplement larger air escape holes that the factory placed in the rear package shelf (Figure 8). In a manner similar to the acella film closure finish treatment of the triangular cutouts, these 25mm holes received automotive hole plugs at the end of the assembly line. Some of the plugs in the early cars were very obvious and stood proud from the plane of the bulkhead, as shown in the Figure 11. In other instances (perhaps beginning in 1973 or so) the holes are almost flush with the bulkhead from the trunk side. BMW may have started inserting the automotive hole plugs from the seat back side, or perhaps these are just impressions of holes that the die cutter made but did not quite cut through-and-through. Some owners report no holes at all, but this seems to be rare. Nevertheless, these holes (or vestiges of the holes) stayed in the same triangular press design as was once removed in the early 1600-2 cars and remained until the end of production of the 02 Series. Like the triangular cutouts before them, these holes are placed under the rear package shelf, and may be strategically placed in an area where trapped air bubbles can escape during the immersion dip. If air bubbles are not allowed to escape during the immersion of the car shell in primer, the spots where the bubbles persist will not be adequately covered by primer during e-coating. Figure 11 Later 02 Series car with automotive hole plug. Arrow points to automotive hole plug installed after painting. Photo: BMW 2002 FAQ As stated above, some holes in the body seem to be designed not only to take in primer, but also to drain primer and expel bubbles after immersion. Examples of these holes are the round holes drilled near the top of the wheelhouse box metal surround on the early Neue Klasse cars (see Figure 3), and the similar, oval shaped holes drilled in every 02 Series car, in the box metal of the wheelhouse arch surround (see Figure 7). Similar holes finished with automotive hole plugs can be found in the spare tire well of all 02 Series cars, presumably for primer drainage. Large holes placed by the factory in the rear parcel shelf are also examples of openings for primer dispersion and air bubble escape (Figure 8). Conclusions As one BMW Group Archivist said regarding the purpose of the triangular cutouts, “This is probably one of those things that are lost in time…” However, with some perseverance, a really good circumstantial case can be made for the open rear bulkhead designs, and various holes in the bodies of these early cars being directly related to the application of primer, whether by gravity dipping or EPD technology. The authors believe that EPD primer processes were fully engaged at the Munich-Milbertshofen factory by the mid-1960s, and that use of anodic EPD technology spread to other BMW plants in the following years. One of the first stops along the way is to see exactly when BMW actually adopted anodic electrophoresis as part of the primer application process. Figures 12, 13, and 14 below, came from the BMW Group Archive. Figure 12 is entitled “BMW electrophoretic dip painting Dip Booth (left) and Drying Oven (right)”. Figure 13 is subtitled “BMW Electrophoresis” and both are dated 1962. This would seem to correspond with the roll-out of the first production Neue Klasse 1500 in 1962. Figure 14 is entitled “Post processing of BMW 1500 after immersion, 1962”. The open rear bulkhead design, and “vent and drain” holes in the wheel housing box metal arch, would seem to be design features for both dispersal of primer to remote interstitial areas (relying too on the extra “throw power” of electrophoretic primer application to get to inaccessible areas of the car’s shell), and holes to open pathways for adequate venting of air bubbles attendant to the immersion process. All of the above notwithstanding, the BMW Group Archive was unable to confirm that the 1962 date on Figures 12, 13, and 14 was an actual date marking the beginning of electrophoretic primer coating, so it could be EPD came to BMW a few years after 1962. Close examination of period photos from the paint shop portion of the production line of early 02 Series sedans would seem to yield similar evidence that the bulkhead holes were related to electrophoretic primer coating. Figure 15 shows an early 02 1600-2 in the foreground of the electrophoretic immersion bath, with a Neue Klasse car ahead in line. Note, in the photo what appears to be an electrical cable coming out of the center rear window opening and into the trunk space. Figure 12 BMW electrophoretic dipping and drying booths, 1962. Photo: BMW Group Archive Figure 13 BMW electrophoretic dip painting, 1962. Photo: BMW Group Archive Figure 14 Post processing of BMW 1500 after immersion, 1962. Photo: BMW Group Archive Figure 15 An early 1600 2 entering the immersion bath labelled “BMW cars of 02 series and “Neue Klasse” during electrophoretic dip. 1966. Photo: BMW Group Archive Final Thoughts and Disclaimers The BMW Group Archive could not (with absolute certainty) verify the dates on some of their photographs, even though the dates are on the photos in their archives. Worst case scenario is that the photos of early electrophoresis plant at the Munich-Milbertshofen factory are a bit later than 1962. This would mean that early Neue Klasse cars could have been primer coated in vats and with paint designed for the gravity adhesion process and not the electrophoretic immersion process. The authors also wish to note that car design often occurred years ahead of assembly line mass production. Since these early 1960s BMW cars were produced at a time when solvent-based and water-based primers utilizing gravity dipping were fading out of the industry, and electrophoretic immersion priming was emerging as the preferred technique, it is possible the newer priming technique simply caught up with an older car design meant for earlier primer techniques. The open bulkheads in early NK cars, and rear bulkhead cutouts of the early 1600-2 sedans, could be vestiges of a design meant to accommodate gravity dipping primers, not electrophoretic dipping. Either way, the authors believe the open construction of the early Neue Klasse cars, and the triangular cutouts in the early 1600-2 cars, are related to design requirements for primer dispersion and air bubble venting (regardless of whether gravity dipping or electro-phoretic deposition primers were used). Acknowledgements The authors wish to thank many people who contributed to this, including a number of people who were contacted through BMW 2002 FAQ. We appreciate your thinking and the photographs contributed for this article. Also thanks so much to Albrecht Walloth of WallothNesch.com, who explained the European laws governing solid rear bulkheads to the writers. Thanks to Chris Bangle, former design chief for BMW, who did not know the answers, but gave a great quote: “Holes are expensive.” Thanks also to Mike Macartney, author of BMW ’02 Restoration Guide, who addressed only the triangular cutouts, but wrote to say “My thoughts are that BMW started off with the cutouts for the reasons you give and then found that there was no need to cut out the sections.” Thanks to Andreas Harz from the BMW Group Archive who wrote several times, but in the end said “This is probably one of those things that are lost in time but if I find something I will tell you.” Big thanks to Ruth Standfuss of the BMW Group Archive, who tirelessly searched for pictures and documents regarding historical records of BMW’s electrophoresis primer endeavors. Thanks to Peter Hope of LVH Coatings Ltd. in the UK, who provided valuable insights as to the triangular cutouts possibly serving as connection points for electrodes, as drain holes for the out-put and input of primer, and the smaller holes being classic venting and draining holes for box metal features. Any and all comments are welcome. Thank you. References Ansdell, D. A. (1999). Automotive paints. Paint and surface coatings: theory and practice, 431-489. Fettis, Gordon, ed. Automotive paints and coatings. VCH Verlagsgesellschaft, Weinheim (Federal Republic of Germany)& VCH Publishers, New York, NY (USA), 1995. Schrader, H. (1979) BMW, A History. Automobile Quarterly Inc. About the Authors Robert P. Smith is a long time sports car fancier and is retired in Hawaii. He has collected and maintained antique sports cars as a hobby for over fifty years. Robert can be reached by personal messaging under the user name @BritshIron through the website BMW 2002 FAQ Dr. Nelson Akafuah is the Associate Director of the Institute of Research for Technology Development, Univerisity of Kentucky. He is the author of both books and scholarly-refereed journals, including “Evolution of the Automotive Body Coating Process--A Review. “ Dr. Akafuah can be reached at [email protected] Adnan Darwish Ahmad is a Ph.D. candidate in the Mechanical Engineering Department at the University of Kentucky and is under the tutorage of Dr. Akafuah. He is the author of multiple scholarly-refereed journal articles focused on painting and coating technology. Adnan can be reached at [email protected] View full article
  3. Understanding the Open Rear Bulkhead Design Features Essential for the Application of Primer Coatings Using Anodic Electrophoretic Deposition on The Early BMW Neue Klasse Sedans and the BMW 02 Series This article offers some explanations for specific design features of the 1960s and 1970s BMW Neue Klasse four-door sedans and 02 Series sedans. The features most closely scrutinized include the open design of the rear bulkheads in early Neue Klasse (NK) cars, triangular cutout holes in solid bulkheads of the early 1600-2 02 Series sedans, and various bulkhead and box metal holes in the trunk areas of all NK and 02 Series sedans. The article seeks to explain the design features that enhance the anodic electrodeposition coating process. The author’s comments are specific to the four-door BMW Neue Klasse Sedans, and the BMW 02 Series which are defined as the BMW’s two-door sedans, including the 1600-2, 1602, 1600ti, 2002, 2002ti, 2002tii, 1802, and 1502 models. Authors Robert P. Smith, @BritshIron BMW 2002 FAQ, USA Nelson K. Akafuah, Ph.D., Univ. of Kentucky Adnan Darwish Ahmad, Univ. of Kentucky Overview During the 1950s and into the early 1960s, entire car bodies were being immersed in vats of primer paint along the assembly line. At first, solvent-based primers were used, which caused environmental hazards and even explosions. For a relatively brief period in the history of automotive primer coating, a water-based primer was used during vat dipping. However, the process still relied on simple gravity to get the primer coated on all parts of the automobile body shell. By the mid-1960s, BMW was using a type of primer coating which utilized electrophoresis in an electrochemical process that would soon be the standard for automotive protective coatings. In the early years of the BMW Neue Klasse cars, the first years of the 02 Series 1600-2 and 1600ti, and the entire remainder of the 02 Series through 1977—these sedans had some holes and openings in the rear bulkhead (the metal partition behind the rear seat back separating the passenger cabin from the trunk space) as well as holes in other parts of the trunk space. There are very few written documents which explain the purposes of these factory design features, and (thus far) no definitive oral history. This article explores the various rear bulkhead types in these early cars. It explains how these openings enhance what BMW called at the time “Electrophoretic immersion bath” or simply “Electrophoresis.” The process is called by many other names, including electro-coating, electro-painting, electrodeposition, and electrophoretic deposition. Electrophoretic deposition (EPD) is the process where specially formulated primer paint is applied after the phosphate pretreatment of the metal substrate to promote long term corrosion resistance. For the anodic EPD process, the metal body shell carries a positive charge, and a uniquely formulated primer resin carries a negative charge. Thus small paint particles are attracted under electrical influence to a positively charged workpiece (the vehicle). The paint forms an insulating film on the metal, which provides a chemical and physical barrier to prevent corrosion. This paint insulation spreads uniformly to otherwise inaccessible areas of the body, and the distance of such spread is known as “throw power.” Adequate primer coating is highly dependent on open pathways for dispersal of pretreatment liquids and primer throughout the body shell, voltage applied to car body and primer, the paint bath temperature, bath non-volatiles, and vehicle duration (immersion time) in the bath. After immersion, time and temperatures in a drying oven are also critical to the process. Assembly Line Pretreatment of the Metal Substrate Before the Electrodeposition Process For optimum protection of the body shell, it imperative to properly prepare the metal surface for the EPD process. The pretreatment allows for a more uniform primer layer. It is chemically driven and in multiple stages, including the following steps: Hot Water Rinsing, Degreasing, Surface Conditioning, and Phosphating Processes. Other critical process parameters are monitored continuously in the pretreatment bath, including the incoming metal quality, water quality, vehicle immersion time, turnover rates, rinse impingement, and surface flow. Adequate liquid filtration is essential throughout the pretreatment stages to maintain excellent corrosion protection and optimal surface quality. The goal of the pretreatment is to have an optimal phosphate crystal structure and coverage on the metal substrate, getting the car ready for electrochemical primer coating. The authors wish to note that these pretreatment steps also require enough adequate openings in the automotive shell so that pretreatment liquids can reach all portions of the body. The Anodic Electrophoretic Deposition Process of the 1960s Anodic EPD technology, introduced in the early 1960s, is an efficient and relatively simple operation with a high degree of automation. The anodic EPD process was subsequently replaced by cathodic technology in the 1970s, the latter which has set new standards in EPD processes and corrosion protection that extends to this day. By 1970, 10% of all vehicles worldwide were electrocoated. By 1990 this had risen to 90% of all vehicles, and today it is by far the most commonly used vehicle coating process (Ansdell, 1999). The liquid primers used in the EPD are often called “electropaints.” Red primers were derived from iron oxide, and grey primers from titanium oxide, mixed with carbon black and yellow iron oxide. In the case of BMW, the company apparently switched from red primer to grey primer sometime around the middle of 1966. Up until 1977, all electropaints used in the automotive industry were of the anodic type, primarily because the resin chemistry was relatively simple, readily available, and adaptable to the needs of the auto industry. In this process, the car was the anode. Figure 1 shows a schematic of the anodic EPD process. The EPD process was reported in great detail by Fettis (Fettis, 1995); a summary is presented here for convenience. A portion of the great success of EDP in the automotive coating process is attributed to throw power. Throw power is a sophisticated yet essential property that defines the ability of an EDP process to deliver primer coating to more remote and harder-to-reach areas. Optimum throw power can depend on a number of technical factors, including pigment volume concentration (which affects film resistance), non-ohmic conductance, rupture voltage, coulomb yield, and neutralizing species type. It is worth mentioning that the typical throw power of the anodic EPD process is about 12-15 cm, while it’s 25-35 cm for the cathodic EPD. The furthest the distance coated and the thickest the film, the better the throw power is. Figure 1 Schematic of the anodic electrodeposition process (Adopted from Fettis 1995) The anodic process had some deficiencies. The two primary weaknesses were phosphate disruption and poor saponification resistance. Note, saponification is a process by which triglycerides are reacted with sodium or potassium hydroxide (lye) to produce glycerol and a fatty acid salt called soap. The best EPD results include resistance to saponification. During the anodic EPD, very high electrical field forces occur, which rupture many of the metal-phosphate bonds (called phosphate disruption). This leads to a weakening of the adhesion of the phosphate coating to the steel substrate. When subsequent paint coats are applied, stresses are set up in the entire paint film, which, when such damage gets to bare metal, tends to cause the entire paint film to curl away from the damage point. In early anodic systems, as soon as corrosion started at any point of damage, the weakened phosphate layer allowed the paint to peel back, exposing more metal, which was chemically clean and very prone to corrosion. This failure was designated ‘scab corrosion.’ This undesirable property was improved by reducing the incidence of rupture of phosphate bonds by merely increasing their number, i.e., modifying phosphate coatings with densely packed, fine phosphate crystals. Such dense phosphate coatings are of low coating weight, and their introduction led to a marked reduction in the incidence of ‘scab corrosion.’ The chemistry of many early anodic primers was characterized by the use of acid resin chemical systems; therefore, poor saponification resistance was inherent in these electropaint primers. As a consequence, the deposited cured primer film (based on acid resins), when exposed to an alkaline environment, will tend to form metal soaps soluble in water. When damage occurs to bare metal, caustic salt will simultaneously attack the steel substrate and the electrocoat film, producing rust and the sodium salt (soap) of the anodic resin. This dissolves the primer coating, leading to a loss of adhesion of the remaining paint film and general corrosion problems (Ansdell, 1999). Electrophoretic Deposition Design Features in BMW Sedans of the Early 1960s Early 1960s BMW sedans (which introduced the now iconic C-pillar “Hofmeister kink”) began with the Neue Klasse (NK) 1500 sedans, introduced in Frankfurt Motor Show in 1961. Figure 2 Neue Klasse BMW of the late Sixties taking a dip in the EPD primer bath. Photo: Schrader (1979) "BMW, A History" These four-door sedans included the NK 1500 (1962-1964), NK 1800 (1963-1968) NK 1600 (1964-1966), and the NK 2000 and variants (1966-1972). Figure 2 shows a later Neue Klasse sedan in the electrophoretic immersion bath. A photo of the rear bulkhead of a 1963 NK 1500 appears below, the green car (Figure 3). Note the two, vertical oval bulkhead cutouts on each end of the partition, and the rather large, more square openings in the center of the bulkhead. The authors believe this open rear bulkhead design helped facilitate dispersal of pretreatment liquids, as well as primer during the vat dipping process. Similarly, the small hole at the top of the wheelhouse arch is likely a “vent and drain” hole that allows the primer-related liquids to enter the box metal, and also promoting a means for air trapped in the box metal to escape. Also, note the vertical, pressed grooves in the sheet metal on either side of the oval cutouts, as well as in the center dividing metal. The oval cutouts have rolled metal edges. All these intricate pressings and punching of the flat metal is done to give the sheet metal the strength and rigidity needed for such an important structural application. It also appears that this bulkhead relies on five separate metal parts to form the skeleton of the bulkhead partition. Finally, BMW installed a trim board on the rear seat back side of the vehicle as a finishing feature. An early Neue Klasse sedan in the assembly line process after final paint is shown in Figure 4. The open design of the rear bulkhead can be clearly seen against the contrast of the trim board. Note the center metal stanchion separating the two largest open areas, and giving some strength to the mid-sections of the bulkhead. Figure 3 Rear bulkhead and wheelhouse of 1963 Neue Klasse 1500. Arrows indicate oval cutouts. The circle at the “vent and drain” box metal hole. Star in large bulkhead opening. Photo courtesy of BMW 2002 FAQ Figure 4 Neue Klasse on Assembly Line. The arrow at center metal divider of bulkhead frame. Photo: BMW Group Archive Sometime in 1964, the rear bulkheads in these NK cars changed from the framed-up cutout design to a solid bulkhead. The trim board was moved outboard of the solid bulkhead, so the trunk had a very finished look. Figure 5 shows a photo of the solid bulkhead with the trim board not yet installed, so you can see a pressed design very similar to what will soon become the familiar rear bulkhead pressing of the 02 Series cars. At the Geneva Auto Show in March 1966, BMW introduced the first of the company’s new 02 Series, the 1600-2. (“2” was to signify two doors, and a way to distinguish this new model from the four-door NK 1600). From the very first 1600-2 in March 1966, as well as early 1600ti cars, there were unique cutouts, die cut from the pressed sheet metal design on either side of the rear bulkhead. These cutout “triangles” remained in the design until approximately the end of November’s production, 1967. Figure 5 Later Neue Klasse Sedan with Solid Rear Bulkhead. Photo: BMW Group Archive After that, the bulkhead returned to the solid form in all 02 Series cars, except for a much smaller hole (25 mm), drilled into the solid triangular pressed bulkhead design that had previously been cut out of the 1600-2 cars. Regarding the cars with triangular cutouts, the factory covered these cutouts with acella film (think translucent plastic sheeting) during final fit and finish procedures. Figure 6 shows the inside trunk of a grey car with the factory acella film installed. Note the black wire and the wiring chase at the top of the wheelhouses, this hole goes through to the cabin of the car. At least one additional hole is present on the box metal forming part of the wheelhouse arch in the trunk of all 02 Series cars, from the first 1966 1600-2 to the last 1502 in 1977. These holes were oval shaped and uncovered (Figure 7). The authors believe BMW designers purposefully included open bulkhead designs in early NK sedans, and the triangular cutouts in early 1600-2 cars, as a way to ensure pretreatment liquids and primer during vat dipping were distributed (as much as possible) throughout the car body. Figure 6 Early1600-2 rear bulkhead with acella film installed. Arrows point to acella film covering triangular cutouts. Photo: Anders Bilidt Figure 7 Oval wheelhouse box metal hole and triangular cutout in a 1967 BMW1600-2. Circle at “vent and drain” box metal oval hole. Arrow points to wire chase penetrating the bulkhead. Star in triangular cutouts that allow for primer distribution and air bubble release during electrophoresis primer immersion. Photo: Robert P. Smith Other holes in box metal components accomplished the same purpose. Drain holes in the spare tire well were similarly intended to provide adequate drainage of primer liquids, similar to the large drains in the cabin floor of the bodies. Holes cut by the factory in the rear package shelf (some call “rear deck, parcel tray, or hat tray”) also allowed for the passage of liquids associated with the primer process, as well as avenues for air bubbles to escape during vat immersion (See Figure 8). These holes in the rear parcel tray were present for the entire production run of the 02 Series, 1966-1977. Figure 8 Factory drilled holes in the parcel shelf of a 1600-2 made in September 1967 helped to disperse liquids associated with the EPD process, and air bubble escape passages during immersion dipping. Photo: Robert P. Smith Such holes, openings, drains, and cutouts provided (1) physical access for all liquids associated with the primer process to flow to all areas of the body, and (2) “vent and drain” opportunities for excess primer products and trapped air to exit the car body during the primer coating process. When electrophoretic immersion was added as part of the primer application process, these various openings became all the more important to assist with throw power requirements of EDP in order to get primer into normally inaccessible areas of the car body, and air bubbles out while the car was being immersed. The authors offer two points of reference that could shed light on the emphasis BMW placed on this relatively new EDP process in marketing the early NK and 02 Series cars. Regarding both the Neue Klasse and 02 Series cars, the YouTube video below depicts the NK/02 Series production line, courtesy of the BMW Group Archive. A full two minutes or more of a 14-minute production documentary is devoted to the electrophoresis process, and how much that process helps the quality of the paint on the finished car. The second point of reference can be found in early BMW 02 sales brochures (Figure 9 and 10), again touting the electrophoretic immersion bath with words like “All the inaccessible corners and edges of the body, outside reach for normal painting, are also covered with anti-corrosive filler.” Note the BMW shown on this brochure is an early 1600-2, with the triangular bulkhead cutouts and covered with red iron oxide primer. The photo and text of this brochure exemplify how BMW can get paint to all the nooks and crannies during the vat dip, demonstrating the throw power of the new EPD primer process at the time. Note the sales brochure in Figure 9 is dated May 1968, but the 1600-2 photo is from an earlier car using red primer. The second brochure (Figure 10) is from August 1968 and features a later 02 Series car in grey primer, with the smaller, 25mm holes in the rear bulkhead. The sales brochure in Figure 10 was captioned "Electrophoresis" Why did these early rear bulkheads finally take on a solid design? For the 02 Series, The Federal Motor Vehicle Safety Standards Act went into effect on January 1, 1968, and mandated solid rear bulkheads as a safety measure to separate the cabin area from the fuel tank on cars. For the Neue Klasse cars, the first impetus to do away with the open rear bulkhead and replace with a solid bulkhead may have been a part of an earlier United Nations agreement which also spoke to fuel safety and cars. Many European countries, including Germany, were signatory to the United Nations Economic Commission for Europe framework, first signed in March 1958. Parts of this agreement, as amended, cover approximately 147 technical regulations on vehicle safety and environmental concerns. Among the subjects covered are mandatory partitions that separate the passenger compartment from the fuel tank, and standards which limit fuel drip into the passenger cabin under crash conditions. Figure 9 A portion of a May 1968 sales brochure touting E-Coating for BMW 1600-2. Photo courtesy of BMW 2002 FAQ Figure 10 Page from a BMW sales brochure from August 1968 showing rear of 02 . Photo courtesy of BMW 2002 FAQ Given that the agreement allows signatory countries to implement the terms of the UN agreement at various times, it may have been that Germany decided to implement the solid barrier separation between the cabin and fuel tank in 1964. In Europe, this rule is often referred to as the ECE 34 Regulations. The USA never signed the above referenced UN agreement, but rather adopted its own vehicle safety standards, as did Canada. The end result was the Federal Motor Vehicle Safety Standards Act, effective January 1, 1968, mandated the solid rear bulkhead to separate the cabin from the fuel tank area (trunk) in a similar fashion to the earlier UN agreement for European cars. All “US spec” or “Federalized” BMW 1600-2 cars, titled as 1968 models and sold mostly through US dealerships such as the Max Hoffman Corporation, were supposed to have solid rear bulkheads. It’s unclear how many BMW 1600-2 cars, made between September and November of 1967, made it to the US as 1968 Federalized cars with the triangular cutouts in the rear bulk-heads. However, it is believed that no US “Federalized” 1600-2 made after November 1967 had the triangular bulkhead cutouts, nor did any 2002, 1802, 1502—no 02 Series car after approximately November 1967. Indeed, the final chapter to this “holes in the rear bulkhead” story goes to BMW 02 Series cars made from December 1967 until the end of production. The authors believe every one of these hundreds of thousands of cars (1502, 1602, 1802, 2002, excepting any “Specials” like the Baur cars) had holes drilled in the very same rear bulkhead panels that had been removed in the early 1600-2 cars. In other words, just because some regulations called for diminishment of early, larger “vent and drainage “ triangular openings for primer dispersion and air bubble escape, it looks like BMW did not give up on the notion of having some way to disperse primer to remote areas of the car’s shell, as well as have holes to allow air bubbles to escape during the EPD immersion dipping process. For paint dispersion, it looks like the holes are positioned to make sure paint gets in the inaccessible cable chases at the top of the wheelhouses (where wheelhouse meets bulkhead) and along welding points. These smaller holes in the bulk-head may also have served to supplement larger air escape holes that the factory placed in the rear package shelf (Figure 8). In a manner similar to the acella film closure finish treatment of the triangular cutouts, these 25mm holes received automotive hole plugs at the end of the assembly line. Some of the plugs in the early cars were very obvious and stood proud from the plane of the bulkhead, as shown in the Figure 11. In other instances (perhaps beginning in 1973 or so) the holes are almost flush with the bulkhead from the trunk side. BMW may have started inserting the automotive hole plugs from the seat back side, or perhaps these are just impressions of holes that the die cutter made but did not quite cut through-and-through. Some owners report no holes at all, but this seems to be rare. Nevertheless, these holes (or vestiges of the holes) stayed in the same triangular press design as was once removed in the early 1600-2 cars and remained until the end of production of the 02 Series. Like the triangular cutouts before them, these holes are placed under the rear package shelf, and may be strategically placed in an area where trapped air bubbles can escape during the immersion dip. If air bubbles are not allowed to escape during the immersion of the car shell in primer, the spots where the bubbles persist will not be adequately covered by primer during e-coating. Figure 11 Later 02 Series car with automotive hole plug. Arrow points to automotive hole plug installed after painting. Photo: BMW 2002 FAQ As stated above, some holes in the body seem to be designed not only to take in primer, but also to drain primer and expel bubbles after immersion. Examples of these holes are the round holes drilled near the top of the wheelhouse box metal surround on the early Neue Klasse cars (see Figure 3), and the similar, oval shaped holes drilled in every 02 Series car, in the box metal of the wheelhouse arch surround (see Figure 7). Similar holes finished with automotive hole plugs can be found in the spare tire well of all 02 Series cars, presumably for primer drainage. Large holes placed by the factory in the rear parcel shelf are also examples of openings for primer dispersion and air bubble escape (Figure 8). Conclusions As one BMW Group Archivist said regarding the purpose of the triangular cutouts, “This is probably one of those things that are lost in time…” However, with some perseverance, a really good circumstantial case can be made for the open rear bulkhead designs, and various holes in the bodies of these early cars being directly related to the application of primer, whether by gravity dipping or EPD technology. The authors believe that EPD primer processes were fully engaged at the Munich-Milbertshofen factory by the mid-1960s, and that use of anodic EPD technology spread to other BMW plants in the following years. One of the first stops along the way is to see exactly when BMW actually adopted anodic electrophoresis as part of the primer application process. Figures 12, 13, and 14 below, came from the BMW Group Archive. Figure 12 is entitled “BMW electrophoretic dip painting Dip Booth (left) and Drying Oven (right)”. Figure 13 is subtitled “BMW Electrophoresis” and both are dated 1962. This would seem to correspond with the roll-out of the first production Neue Klasse 1500 in 1962. Figure 14 is entitled “Post processing of BMW 1500 after immersion, 1962”. The open rear bulkhead design, and “vent and drain” holes in the wheel housing box metal arch, would seem to be design features for both dispersal of primer to remote interstitial areas (relying too on the extra “throw power” of electrophoretic primer application to get to inaccessible areas of the car’s shell), and holes to open pathways for adequate venting of air bubbles attendant to the immersion process. All of the above notwithstanding, the BMW Group Archive was unable to confirm that the 1962 date on Figures 12, 13, and 14 was an actual date marking the beginning of electrophoretic primer coating, so it could be EPD came to BMW a few years after 1962. Close examination of period photos from the paint shop portion of the production line of early 02 Series sedans would seem to yield similar evidence that the bulkhead holes were related to electrophoretic primer coating. Figure 15 shows an early 02 1600-2 in the foreground of the electrophoretic immersion bath, with a Neue Klasse car ahead in line. Note, in the photo what appears to be an electrical cable coming out of the center rear window opening and into the trunk space. Figure 12 BMW electrophoretic dipping and drying booths, 1962. Photo: BMW Group Archive Figure 13 BMW electrophoretic dip painting, 1962. Photo: BMW Group Archive Figure 14 Post processing of BMW 1500 after immersion, 1962. Photo: BMW Group Archive Figure 15 An early 1600 2 entering the immersion bath labelled “BMW cars of 02 series and “Neue Klasse” during electrophoretic dip. 1966. Photo: BMW Group Archive Final Thoughts and Disclaimers The BMW Group Archive could not (with absolute certainty) verify the dates on some of their photographs, even though the dates are on the photos in their archives. Worst case scenario is that the photos of early electrophoresis plant at the Munich-Milbertshofen factory are a bit later than 1962. This would mean that early Neue Klasse cars could have been primer coated in vats and with paint designed for the gravity adhesion process and not the electrophoretic immersion process. The authors also wish to note that car design often occurred years ahead of assembly line mass production. Since these early 1960s BMW cars were produced at a time when solvent-based and water-based primers utilizing gravity dipping were fading out of the industry, and electrophoretic immersion priming was emerging as the preferred technique, it is possible the newer priming technique simply caught up with an older car design meant for earlier primer techniques. The open bulkheads in early NK cars, and rear bulkhead cutouts of the early 1600-2 sedans, could be vestiges of a design meant to accommodate gravity dipping primers, not electrophoretic dipping. Either way, the authors believe the open construction of the early Neue Klasse cars, and the triangular cutouts in the early 1600-2 cars, are related to design requirements for primer dispersion and air bubble venting (regardless of whether gravity dipping or electro-phoretic deposition primers were used). Acknowledgements The authors wish to thank many people who contributed to this, including a number of people who were contacted through BMW 2002 FAQ. We appreciate your thinking and the photographs contributed for this article. Also thanks so much to Albrecht Walloth of WallothNesch.com, who explained the European laws governing solid rear bulkheads to the writers. Thanks to Chris Bangle, former design chief for BMW, who did not know the answers, but gave a great quote: “Holes are expensive.” Thanks also to Mike Macartney, author of BMW ’02 Restoration Guide, who addressed only the triangular cutouts, but wrote to say “My thoughts are that BMW started off with the cutouts for the reasons you give and then found that there was no need to cut out the sections.” Thanks to Andreas Harz from the BMW Group Archive who wrote several times, but in the end said “This is probably one of those things that are lost in time but if I find something I will tell you.” Big thanks to Ruth Standfuss of the BMW Group Archive, who tirelessly searched for pictures and documents regarding historical records of BMW’s electrophoresis primer endeavors. Thanks to Peter Hope of LVH Coatings Ltd. in the UK, who provided valuable insights as to the triangular cutouts possibly serving as connection points for electrodes, as drain holes for the out-put and input of primer, and the smaller holes being classic venting and draining holes for box metal features. Any and all comments are welcome. Thank you. References Ansdell, D. A. (1999). Automotive paints. Paint and surface coatings: theory and practice, 431-489. Fettis, Gordon, ed. Automotive paints and coatings. VCH Verlagsgesellschaft, Weinheim (Federal Republic of Germany)& VCH Publishers, New York, NY (USA), 1995. Schrader, H. (1979) BMW, A History. Automobile Quarterly Inc. About the Authors Robert P. Smith is a long time sports car fancier and is retired in Hawaii. He has collected and maintained antique sports cars as a hobby for over fifty years. Robert can be reached by personal messaging under the user name @BritshIron through the website BMW 2002 FAQ Dr. Nelson Akafuah is the Associate Director of the Institute of Research for Technology Development, Univerisity of Kentucky. He is the author of both books and scholarly-refereed journals, including “Evolution of the Automotive Body Coating Process--A Review. “ Dr. Akafuah can be reached at [email protected] Adnan Darwish Ahmad is a Ph.D. candidate in the Mechanical Engineering Department at the University of Kentucky and is under the tutorage of Dr. Akafuah. He is the author of multiple scholarly-refereed journal articles focused on painting and coating technology. Adnan can be reached at [email protected]
  4. Looks like Joysterm is doing an evasive maneuver to me--no masks!
  5. @cdn97986 Thanks again for contributing your expertise. As I understand your point above, you are saying that e-coating basically revolutionized the way in which automobile bodies were and are protected in the primer coat process, beginning in the 1960s. I think some of the interest in this thread goes to why our old cars display such a tendency to rust and corrode. which seems to be related to the type of e-coating used when our Neue Klasse and 02 cars were made. Correct me if I'm wrong, but I think some of the poor paint performance in these older cars goes to the fact that they were subjected to anodic e-coating, as opposed to the more recent and better cathodic e-coating. Also, I was wondering whether cathodic electro-coating offers better throwpower than anodic e-coating, in addition to being better at preventing corrosion? This question is related to whether our older cars have poorer protection in the hard-to-paint areas due to the reduced throwpower in anodic e-coating, or whether the nooks and crannies got coated okay with anodic e-coating, but the poor "resistance to corrosion" factor inherent in anodic e-coating caused any anodic coated surface to break down over time. Speaking of time, we are talking about cars that are 40+ years old! Maybe this whole paint issue is just part of the hobby when it comes to care-taking these antique automobiles, along with dealing with the primer technology that was available when they were made. Aloha and mahalo! Robert
  6. I got a look at a book entitled: "Automotive Coatings Formulation: Chemistry, Physics, and Practices by Ulrich Poth. It speaks to many of the issues raised in this thread, paraphrased as follows: 1. Early vat primer dipping of self-supporting car bodies (prior to electrophoresis) involved solvent-borne primers and was relatively dangerous. Explosions were not uncommon, and insurance costs were high. 2. Water-borne dipping primers were developed, and while eliminating the risk of explosion, the primers had a tendency to cause finish defects, like sagging and cratering. Water-borne gravity vat dipping enjoyed only a short reign in the automobile coating industry, from roughly 1960-1965. 3. Electro-deposition coating was developed in the mid-1960s, according to this author. Properly done, electro-deposition (utilizing electrophoresis) yields smooth coats covering all the metal parts at the same film thickness, and can be extensively automated. 4. The first method of electro-deposition used for automotive coating was anodic electro-deposition, in which the car body was the anode or positive pole, and the primer particles were negatively charged. 5. Anodic deposition primers were colored, with pigments either coming from iron oxides (red primers) or titanium oxides tinted with carbon black and yellow iron oxides, to form a grey colored primer. 6. Corrosion resistance in anodic primers is not optimal. The reason (as pointed out above) is iron oxidation at the car body which causes a weak point in corrosion resistance. 7. The author says cathodic electro deposition was developed in the mid-1970s, and offered much better corrosion resistance. I have really streamlined the information from this book, but check it out if you want to learn more. I am still amazed that BMW apparently had anodic primer electro-deposition in an industrial setting as early as 1962. I'm going to try to drill down on this a bit more, just to make sure the early Neue Klasse cars were not simply vat dipped without electrophoresis, but the evidence right now says e-coating was always part of Neue Klasse primer dip treatment. More later on this topic. Thank you. Robert
  7. Toby, I think it's because anodic electrophoresis really ain't that hot. It saved auto companies a heck of a lot of paint, by thinly coating the metal evenly, and thoroughly, and allowing for recycling of most of the unused primer. But (as pointed out above), anodic primer e-coating in these early cars did not do a great job at stopping corrosion once it set in. As I see it, anything close to the ground or regularly exposed to the elements got hammered over time. But check out the box metal in the 02 trunk (near the wheelhouse and trunk lid lever), with the little oval hole for primer dispersal and draining. You don't see rust too often there, because it's otherwise protected (see picture from my car). Anyway, it's sort of a big point coming out in this thread. What did BMW know about the (much better) cathodic e-coating, and when did they know it? Aloha, Robert
  8. @cdn97986: Thanks for weighing in with your experience. Just to put this thread in context, I was trying to drill down on the Neue Klasse and 02 Series cars and their factory primer e-coating, not the more modern models. I got interested in the primer process after researching some design elements of the early to mid-60s BMW sedans. For instance, take a look at the rear bulkhead of this early Neue Klasse sedan (first photo). The light areas are a trim board just behind the rear seat back. Why would designers make the metal rear bulkhead in such a "stick frame" fashion? Then it occurred to me it must have something to do with paint delivery requirements to hard-to-paint areas, including the bulkhead, wheelhouses, inner fender areas, etc. Looking at old brochures and the factory production film (below) sort of sealed the deal for me. BMW was very proud of their (at the time) revolutionary "electrophoresis" primer process. Plus, in those days, they were selling cars to a very technically astute client audience. I was surprised to see the old pictures of the anodic paint plant (above) in the archives dated 1962. While this was the first year of production of the Neue Klasse 1500, I had not heard of a major automobile manufacturer having anodic primer e-coating as a production tool as early as 1962. I thought sure the open rear bulkhead design was part of a gravity dip primer application system. But, maybe the anodic primer coating was part of the larger success story for the Neue Klasse sedans, which saved BMW's bacon during some lean times. I am also surprised to find pictures and references to "surface anodic immersion primer, 3 series" and "anodic dip primer, 3 series" as late as 1981. I suppose BMW could have been using cathodic e-coating for other models in 1981, while at the same time still using anodic dip coating for the 3 series, but it just seems unlikely. The earliest reference I can which mentions BMW cathodic e-coating is a parts production plant at the Dingolfing plant in 1973. I believe the first BMW sedan to emerge from the Dingolfing plant was a 5 Series car. I also believe all the factory Neue Klasse and 02 Series cars were made at the Munich plant, not counting the Complete Knock-Down cars. And I'm assuming all the Neue Klasse and 02 cars were subject to the anodic immersion primer e-coating. Take a look at the production video below. You'll see both Neue Klasse four door sedans, and the 02 Series cars, with quite a bit of time devoted to "electrophoresis." See also early production 02 e-coating photo. Aloha, Robert PS. @HBChris Yes, the grey primer is the e-coat on these older cars. I don't know much about the history of extra factory undercoating on these early cars. I think @Conserv has posted previously on the subject. RPS
  9. @uai Here's a little more of a report on the primer color and ATL versus KTL. Ruth Standfuss from the BMW Group wrote me back, and is going to check some original catalogs from the archives and get back to me at a later date. She's been super helpful. Attached is a picture from the inside wall of my trunk space, right behind the license plate light mounting. The original Chamonix paint is scratched a bit at that location. It looks like my primer was grey. My build record is: "The BMW 1600 US VIN 1560629 was manufactured on September 28th, 1967 and delivered on October 06th, 1967 to the BMW importer Hoffman Motors Corp. in New York City. The original colour was Chamonix, paint code 085." I've got a conference call on Wednesday with some guys at the University of Kentucky who are experts on the the history of the use of e-coating in the automotive industry. I will definitely bring up the matter of red primer versus grey primer, and the possibility that one was the formulation for anodic e-coating, and the other formulated for cathodic e-coating. I got some pictures of old brochures from @Conserv and he says the red car in the top brochure in the stack below is from May 1968, and the bottom one is from August 1968. Notice the May 1968 brochure has the red primer car, and the August 1968 brochure appears to have the grey primer, and is a solid rear bulkhead car built sometime on or after December 1967. Both pictures were probably months old when used in the brochures, as the red car is obviously is an early 1600-2, and those triangular cutouts in the bulkhead went away in November 1967 (maybe, as you say, a red primer 1600-2 was much earlier). My car made in September 1967 has grey primer. If the brother of the Dingolfing Plant manager is correct, and grey primer signals cathodic dipping, then the change to cathodic e-coating would have occurred sometime prior to September 1967. From what I have been able to read about cathodic e-coating, KTL did not come into commercial use until the 1970s. Another mystery to solve! But, communications like the one you cite with the Dingolfling Plant manager is one way these old secrets may be uncovered. Thanks so much for adding to the richness of this discussion. Robert PS. Also below see a Neue Klasse four door sedan with red primer. RPS
  10. @MitchaPaLoOza88 Most definitely, the four threaded and sealed plugs in the floor pan are for draining out the primer during a vat dip. Another FAQ'r, Son of Marty, also points out the holes were first used to align the floor pan on the assembly jig during the pre-robotic era. So, those big holes had at least two purposes, all related to production and not too useful after the car has been assembled and painted. As to the three holes in the spare tire well, my guess would be they were primer drain holes. Guaranteed the automotive hole plugs were not installed until after the paint was dry! I guess you could pull them out to drain water from the tire well, but if you ran the car without those plugs, the cabin may stink up from exhaust fumes, like it does when your trunk lid seal is kaput! Aloha, Robert (link)
  11. Aloha, Uai. My car was made in September 1967, and I will check to see the primer color. I will also write the BMW Group now and see if they can give me a definitive answer. It seems to be a subject that is fading in the historical record, so if you have any proof of when BMW changed from anodic (ATL) to cathodic (KTL) please post. What I did was a "simple search" on the BMW Group website, and by entering the word "anodic" I got the reference to anodic electrophoresis being done as early as 1962, and a late photo captioned "Anodic primer dip" with Series 3 cars in 1981, as shown above. A search of cathodic electrophoresis or KTL yielded some parts being treated at the Dingolfing plant in 1973, but the only cars I could find made at Dingolfing were Series 5. I think the Neue Klasse and 02 Series were made at the Munich plant. I have no information on how the body parts were treated for the knock-down cars. Anything you can discover would be very much welcomed. Thank you. Robert
  12. Yes, electrophoretic immersion, electro-coating, electro-painting, electrochemical coating, electrodeposition, and e-coating are all pretty much the same thing in the context of these BMW primer techniques. If the dates above hold up, the good part of the story is that BMW apparently started e-coating primer back in 1962, which is several years ahead of what most of the literature indicates this process was widely used in the automobile industry. The bad news is BMW apparently did not switch from anodic e-coating to cathodic e-coating until after the Neue Klasse and 02 Series were all done. I ran across some references indicating cathodic deposition was used first by BMW at the Dingolfing plant, but apparently not until the production of more modern Bimmers. As I understand it, the original e-coat processes were all anodic and did not provide very good "spread of corrosion" protection for the steel. The cathodic processes, starting in the early 1970s by many car companies, reduced spread of corrosion, but still had some less-than-perfect issues. The cathodic e-coating process was later perfected by zinc plating the steel prior to e-coating. There's a bunch of chemistry involved, and anodic e-coating required a very different primer formulation than cathodic e-coating. For instance, anodic paint particles become unstable and bind to the metal at low pH conditions, and cathodic primers have particles binding at high pH levels on the metal surface. Think about the difficulty of paint protection when dealing with hidden spaces like those involved with the 02 Series fresh cabin air flow system! (below). As imperfect as anodic e-coating was and is, it was still very useful in the design and production of these early cars. I hope the above is accurate, but I'll be the first to admit I'm still learning. It's a fascinating topic, though. If you consider BMW auto production as having Auto Design as sort of an umbrella, then you have the Press Shop, the Body Shop, the Paint Shop, and the Assembly Shop. Designing the cars has to match up with all four shop needs. All pretty interesting. Thank you. Robert
  13. I did some research on the BMW Group site, and I think I've answered my own questions! Thanks to anyone who gave this some thought. 1. I was wondering if the early Neue Klasse four door sedans were painted with primer using a gravity dip vat, then later Neue Klasse cars primed using electrophoretic dip immersion. I found two photographs on the BMW Group site that are captioned "BMW electrophoresis, 1962." (see below). These photos appear to show a brand new electrophoresis paint plant. So, if the date is correct, it means all Neue Klasse four door cars and the 02 Series used electrophoresis to apply primer. This is pretty cool, as 1962 was a really early for industrial scale electrophoresis coating. By the way, one real advantage of using this technique is the primer goes on in an equally thin layer, and uniformly to every nook and cranny. When the body shell is electrically charged to attract the paint particles, there is a natural point where the primer can become thick enough to create an insulation effect, and therefore no more primer will adhere to the metal. If the plant operator cuts off the charging process at an exact time during the dip immersion, the layer of primer will be exactly the same thickness for the entire body shell and all its cavities. 2. Here's what I believe to be the answer to questions 2 and 3 above, regarding anodic versus cathodic immersion dipping. I found a picture on BMW Group that is entitled "Production automobile: Anodic primer dip, 3 Series, 1981". So, if BMW was still using anodic dipping in 1981, that means all of the Neue Klasse four door cars and all the 02 Series cars were primed using anodic e-coating, not cathodic. Sort of a nerdy topic, but fascinating. Thanks for reading. Robert
  14. A quick overview of this inquiry. I am trying to determine whether BMW used all three methods of applying primer by tank dipping at the factory for Neue Klasse and 02 Series cars, and when each method was first used and subsequently discontinued. The first method was utilized in the 1950s, and applied primer using gravity dipping paint primers. There was no electrical charge used for these gravity primer vat dips. Then, BMW advertised its electrophoretic immersion bath process for Neue Klasse and 02 Series cars, both in sales brochures and in factory production films. Initially, electrophoretic automotive paint coating (e-coating) developed on an industrial scale using anodic paint dipping (anodische Tauchlackieran or ATL). Most of the literature on anodic primer dipping indicates it was in use during the mid-1960s. With anodic dipping, the car shell would be cabled to achieve a positive charge (the anode) and the surrounding paint particles would be negatively charged (the cathode). For a variety of reasons, anodic dipping is not as protective of the body shell metal as is cathodic dipping (kataphoretische Tauchlackierung or KTL). Cathodic dip painting is when the body shell is negatively charged and paint particles are positively charged. However, cathodic dipping as an e-coat method for automobiles was not developed fully until sometime in the 1970s. Different primers must be used depending on whether the coating process is anodic or cathodic. These are the things I'd like to know: 1. Were any of the early Neue Klasse sedans (ie, 1962 1500) painted with primer using the gravity vat dip process for primer, and if so when did that practice end? 2. Were later Neue Klasse and early 02 Series sedans subjected to the anodic dipping process during their first years of production, and did the factory later convert from anodic to cathodic dip painting? If there was such a conversion from anodic to cathodic, when did that occur? 3. Is it possible the BMW factory stayed with anodic paint dipping for the entire run of the Neue Klasse sedans and 02 Series sedans, 1960s through the end of production in the late 1970s? Thanks so much for your thoughts and knowledge. Robert (high resolution link below) https://www.bimmerarchive.org/photo/3884-53-bmw-plant-munich.html
  15. Les, I think "the die is cast." It's a No Reserve auction. My experience with BaT is that it is very difficult to get out of your contractural agreement to sell, so this car will sell to the highest bidder. I don't think the video will attract many additional bidders. However, the window shades and the meatballs, now there's the "cat's meow!" Aloha, Robert. PS. I think low teens is all the money. RPS
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