Chrome plating (less commonly chromium plating) is a technique of electroplating a thin layer of chromium onto a metal object. A chrome plated part is called chrome, or is said to have been chromed. The chromium layer can be decorative, provide corrosion resistance, facilitate cleaning, or increase surface hardness. Sometimes, a less expensive substitute for chrome such as nickel may be used for aesthetic purposes.
Chromium compounds used in electroplating are toxic. In most countries, their disposal is tightly regulated. Some fume suppressants used to control the emission of airborne chromium from plating baths are also toxic, making disposal even more difficult.
The preparation and chrome plating of a part typically includes some or all of these steps:
Surface preparation
Manual cleaning to remove dirt and surface impurities
Removal of remaining organic contaminants using emulsion cleaning, alkaline cleaning, anodic electrocleaning, or solvent cleaning by immersion, spray, manual application, or vapor condensation
Rinsing
Activation or electroetching
Rinsing (not necessary if the activation and plating steps are done in the same bath)
Immersion in the chrome plating bath, where the part is allowed to warm to solution temperature
Application of plating current for the required time to attain the desired thickness
Rinsing
There are many variations to this process, depending on the type of substrate being plated. Different substrates need different etching solutions, such as hydrochloric, hydrofluoric, and sulfuric acids. Ferric chloride is also popular for the etching of nimonic alloys. Sometimes the component enters the chrome plating vat while electrically live. Sometimes the component has a conforming anode made from lead/tin or platinized titanium. A typical hard chrome vat plates at about per hour.
Some common industry specifications governing the chrome plating process are AMS 2460, AMS 2406, and MIL-STD-1501.
Hexavalent chromium plating, also known as hex-chrome, Cr6+, and chrome (VI) plating, uses chromium trioxide (CrO3, also known as chromic anhydride) as the main ingredient.