Automobiles nickel coatings

The electroless deposition technique has a special application in the chromium plating of plastics, particularly for automobiles. A primary nickel coating is nsed to obtain the conducting layer necessary for the subsequent electrodeposition of chrominm or other metals. A common practice is to coat the electroless Ni first with Cu, then with more Ni and finally with very thin Cr, all by electroplating techniques. 

MG = mixed glass MGF = milled glass fibre Ml = medium impact mod. = modified grade MPG = micronized powder grade MR = mould release MV = medium viscosity NA = non-automobile NCGF = nickel coated graphite fibre... 

Chromium plated parts on automobiles consist of steel substrates with an intermediate layer of nickel, or in some cases, layered deposits of copper and nickel. The thin chromium deposit provides bright appearance and stain free surface while the nickel layer provides the corrosion protection to the steel substrate. With this system it is essential that the nickel cover the steel substrate completely because the iron will be the anode and nickel the cathode. Any breaks or pores in the coating will result in the condition shown in Figure 16.3. This figure illustrates the reason for the corrosion of chrome trim on automobiles after World War II. 

Advancements in materitJs have been one of the most important factors in the development of corrosion-resistant automobiles. For automobile body and chassis parts, use of precoated sheet steel in critical areas, as demonstrated in Fig. 5, is one of the most effective methods of combating corrosion. Early on, hot dip gttlvanized steel and Zincro-metal coated steel were used to prevent perforation corrosion from the inside out in auto-body applications. Today a wide range of materi tls is used including hot dip and electrodeposited zinc, zinc-iron, zinc-nickel, and zinc-nickel/ organic composite coated steel. Other materials include aluminum and aluminum-zinc coated steels for exhaust systems and some structural components, teme (tin-lead) coated steel for fiiel tanks, and tin coated steel [23-25],... 

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