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Black chrome plating is a coating of chromium, electrostatically applied to a metal surface such as the wheel of an automobile or a motorcycle's exhaust pipe. The chromium has been chemically adulterated to achieve the black color. This type of plating is unique in its appearance, exhibiting not only the high reflectivity of polished chrome, but also a “depth” not readily evident in other polished finishes. A black chrome finish is hard and durable, and provides a measure of rust and corrosion resistance, largely because of the need for under-coats of copper and nickel plating.
Highly polished black chrome plating is used as a decorative surface for visible parts of cars and motorcycles, as well as for some household fixtures such as faucets. Matte finish plating is also used on the inside of telescopes and microscopes, and other areas where light reflection would interfere with the use of enjoyment of the device. This type of plating is costly, though, about three times as expensive as “regular” chrome plating, which itself is relatively expensive at $100 - $150, on average, per automobile wheel. More complex wheel designs, such as wire spokes, can cost considerably more because of the extra work involved.
Black chrome plating is so costly because the process, when done properly, is labor-intensive and time-consuming. An object to be chrome-plated must be thoroughly cleaned and prepared for plating in an electrostatic bath, and first plated with copper and then nickel before the chrome plate is applied. After each stage in the process, the object must be prepared for the next step. The materials used in both the cleaning and the plating processes are caustic and hazardous, and often carcinogenic, adding significant costs for compliance with environmental protection standards. In addition, the chemical compounds used in the plating process itself must be altered to impart the black tint to the final chrome plate.
There are less costly alternatives to black chrome plating, such as combinations of black paint and clear coat paint, or powder coating. The former is self-explanatory — black paint is applied in multiple coats, then over-painted with a clear coat. Coats are buffed after every application to achieve perfect smoothness and ensure maximum gloss. Powder coating is more complex, involving coating the work surface with electrostatically-charged powder, either by spraying or dipping, and then heat-curing it, melting the powder so that it forms a smooth surface. Aficionados insist that powder coating is aesthetically identical to black chrome, but there are limitations to powder coating in automotive applications — such items as exhaust pipes, which achieve very high temperatures, will quickly destroy powder coats applied to them.
Let's not forget that black chrome looks awesome on some wheels. The extra cost may be worth it. It's rare enough to be distinctive, but common enough so that you have a lot to choose from.
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