Black chrome plating is a coating of chromium that has been chemically altered to achieve a black color. The chromium is applied electrostatically to a metal surface, such as an automobile wheel or a motorcycle exhaust pipe.
Black chrome plating has a unique appearance, exhibiting not only the high reflectivity of polished chrome, but also a depth not seen in other polished finishes. A black chrome finish is hard and durable, and provides some protection against rust and corrosion, largely because of the need for under-coats of copper and nickel plating.
Uses of Black Chrome Plating
Highly polished black chrome plating is used as a decorative surface for visible parts of cars and motorcycles, as well as for household fixtures such as faucets. In contrast, matte finish black chrome plating is used on the insides of telescopes and microscopes, and other areas where light reflection would interfere with the operation of the device.
Black chrome plating is costly, often costing about three times as much as “regular” chrome plating. Even regular chrome plating is relatively expensive, at an average of $100 - $150 per automobile wheel. More complex wheel designs, such as wire spokes, can cost considerably more because of the extra work involved.
The Plating Process
Chrome plating is costly because the process, when done properly, is labor intensive and time consuming. In the standard triple-plating process, an object must first be cleaned thoroughly and prepared for plating in an electrostatic bath. It is plated with copper and then with nickel before the chromium 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 black chrome plating, the chemical compounds used in the plating process must be altered to impart the black tint to the final chrome plate.
Caring for Black Chrome Plating
- Black chrome plating is more susceptible to scratching and stains than regular chrome plating, and it requires slightly different care.
- Black chrome should be regularly cleaned with fresh water, using a microfiber towel, to wipe away dirt and brake dust. A gentle, diluted cleaner should be safe to use with black chrome.
- Abrasive surfaces and abrasive chrome polish should never be used on black chrome plating. Make sure that you choose a chrome polish that is safe for black chrome, and use a clean towel to buff it off.
- Finishing off with high-quality automotive wax that is safe for clear coats is a great way to keep black chrome plating looking its best.
Alternatives to Black Chrome Plating
Combining black paint and clear coat paint is a less expensive alternative to black chrome plating. 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 another alternative to black chrome plating. Powder coating involves 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.
Some enthusiasts insist that powder coating is aesthetically identical to black chrome. However, there are limitations to powder coating in automotive applications. Items such as exhaust pipes, which achieve very high temperatures, will quickly destroy powder coats applied to them.
How Is Black Chrome Plating Done?
A trained plater applies black chrome plating using an electroplating process. First, the object is cleaned to prepare it for plating; this may involve sanding, grinding or chemical etching. Then it is placed in the electroplating vat. The electroplating vat has several components.
The electrolyte is a solution of salt and ions of the plating metal; for example, when plating an item with copper, the electrolyte contains copper ions. The solution may contain additional chemicals, such as potassium cyanide.
A cathode is a negatively-charged electrode. The object being plated serves as the cathode in black chrome plating; for example, a metal wheel rim. The material the object is made of is called the substrate.
Black chrome plating requires a direct electrical current to the anode. With the electrodes immersed in the electrolyte solution, the electroplater turns on the power supply. The metal ions in the anode and the solution oxidize; this means they take on a positive charge. The positively-charged metal ions are attracted to the negatively-charged cathode and adhere to it, producing a thin metal coating.
For example, when coating a metal wheel rim with copper, the plater begins by cleaning the wheel to prepare it for plating. He or she then immerses the rim, which will serve as the cathode or negative electrode, in an electrolyte solution of salt and copper ions. A copper anode is placed in the solution and the plater turns the power on. The copper ions oxidize and move to the wheel rim, depositing a copper coating on the rim.
To produce a black chrome finish, the plater must repeat this process a second time with nickel and a third time with black chromium.
How Much Does Black Chrome Plating Cost?
Because black chrome plating is a longer process than normal chrome plating, you should expect to pay more for black chrome than normal chrome. The cost of black chrome plating takes into account many factors.
The thin, reflective chrome layer highlights every flaw in the substrate, so the plater must prepare the surface before electroplating. Often, the preparation takes more time and labor than the plating. If the part is old, rusty or damaged, preparation takes longer and costs more.
Electroplating consumes a lot of electricity, and black chrome plating, which requires multiple layers, consumes more. Shops must consider utility costs when setting their prices.
Electroplating chemicals are harsh and sometimes toxic. Shops must follow strict safety regulations, which add to operating expenses.
While one does not need formal certification to do black chrome plating, it does require training and skill. An electroplater should have a steady hand, good manual dexterity and the ability to follow instructions and adhere to safety procedures. More experienced platers generally charge more.
Hazardous Waste Disposal
Shops must dispose of black chrome plating chemicals properly; they can't simply pour them down the drain. Disposing of hazardous chemicals requires extra work and cost for the business, so this is reflected in the price.
What Is the Difference Between Chrome and Black Chrome?
While chrome and black chrome are both chromium, there are some differences between the two. The most obvious difference between chrome and black chrome is color. The dark finish of black chrome is achieved by adding other metals to chromium.
Black chrome and regular chrome require different care, as black chrome scratches more easily. However, it also may provide better protection against rust and corrosion because of the multiple layers of coating.