By Jim Kerr
Beautiful paint looks great, but nothing makes a car stand out like some tasteful and well-placed shiny chrome. Chrome — or more correctly, Chromium — is a naturally-occurring chemical element and you might be surprised to find out that it really isn’t shiny: it’s what’s underneath that makes the chrome stand out.
Chrome can be applied to many metals: steel, aluminum, brass, copper and nickel. It can even be applied to plastic, although most commonly the plastic “chrome” interior trim and automotive grilles we see are really plastic coated with a thin layer of aluminum. Real chrome is applied using an electroplating process. Electrical current is directed through the part to be plated while it is immersed in a liquid bath of Chromium solution. The Chromium forms a thin layer only a few millionths of an inch thick on the part, giving it a bright bluish tint.
Industrial chrome can be electroplated directly to the base metal, where a layer several thousands of an inch thick can be deposited to provide a good wearing surface, such as on the shaft of a hydraulic cylinder. The decorative chrome we see on automotive parts starts with a layer of nickel. In fact, the shiny parts on cars before the 1920’s were all nickel plated and it is this nickel that still gives chrome its shiny look. However, nickel can tarnish so the parts would look dull after some time. To prevent this tarnishing, a thin layer of chrome is plated over the nickel and give it a long lasting and durable finish.
Show chrome, triple plated chrome and double nickel chrome are all names for the same thing. They refer to the aftermarket process used to produce the mirror-like finishes we see on show car parts. First the metal part is stripped, cleaned and repaired. Then is it cleaned again. Several different chemical rinses are used to thoroughly clean the part.
Then the part is electroplated with a layer of copper. The copper fills small irregularities in the metal and is relatively soft, so it can be polished to a smooth finish. Sometimes the part may need several layers of copper, each being polished before the next layer is plated, so that a perfectly smooth surface is produced. The smoother the surface, the better the chrome will look.
After the copper plating and more rinses and cleaning, a layer of nickel is electroplated to the surface. The layer of nickel produces the shine and the best “show chrome” will often have two layers of nickel applied. Again, the part is cleaned before the final layer of chromium is applied, protecting the nickel and providing that long lasting finish.
Quality chrome finishes are expensive. The many chemical baths and plating process take a lot of time, but much of the cost comes from the time spent polishing the parts between the plating layers to produce a smooth finish. Two shops may use the same process, but the best shop will have skilled people doing all the metal prep and polishing. Just as with a quality paint finish, most of the work is hidden beneath the surface.
While it is possible to electroplate chrome plate on plastic it is a difficult and expensive process. Vacuum metalizing is the most common process used for a chrome look on plastic but it doesn’t have the durability or corrosion resistance of chrome plating. During the vacuum metalizing process aluminum is evaporated in a vacuum chamber, which than condenses back on and bonds to the parts to form a uniform layer, which shines like chrome. A protective clear topcoat is applied, although dyes can be added for that special effect. This type of chrome should only be cleaned with a damp, soft rag or the surface can become damaged.
Recently, a painting process has been developed that can give that “chrome” look. A base primer is sprayed on the part, then a layer of metal is sprayed from the paint gun and finally a top clear coat is applied to provide protection. This finish can be applied on smooth or textured surfaces of almost any solid material for that custom look, but it must be cared for just like an automotive paint finish.
Chrome accents can set a vehicle apart in the crowd. The next time you see really nice chrome, appreciate the time and workmanship that goes into prepping the parts, for that is where the real craftsmanship is.