Chromium Chrome Finishing Plating Specification Electroplating
QQ-C-320, Chrome, Chromium Plating
Chrome plating (less commonly chromium plating), often referred to simply as chrome, is a technique of electroplating a thin layer of chromium onto a metal or plastic object. The chromed layer can be decorative, provide corrosion resistance, ease cleaning procedures, or increase surface hardness. Sometimes a less expensive imitator of chrome may be used for aesthetic purposes.
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 electrically live. Sometimes the component has a conforming anode made from lead/tin or platinized titanium. A typical hard chrome vat plates at about 1 mil (25 µm) per hour.
Various linishing and buffing processes are used in preparing components for decorative chrome plating. The overall appearance of decorative chrome plating is only as good as the preparation of the component.
The chrome plating chemicals are very toxic. Disposal of chemicals is regulated in most countries.
Excellent hardness (Rc 68-74), wear resistance and erosion resistance. Has low coefficient of friction, and is resistant to heat. In addition to above properties, can be rendered porous for lubrication purposes.
Type I Bright
Type II Satin
Class 1 .00001" min. chrome on all visible surfaces. Corrosion protection finish or the "Decorative" finish used in a conjunction with copper and nickel as under coatings prior to the chrome finish.
Class 2 Thickness should be specified on requirements documents. Plate directly on base metal.
Class 2a: Plated to specified dimensions or processed to specified dimensions after plating.
Class 2b: Parts below Rc 40 and subject to static loads or designed for limited life under dynamic loads.
Class 2c: Parts below Rc 40 and designed for unlimited life under dynamic loads.
Class 2d: Parts have hardness of Rc 40 or above and subject to static loads or designed for limited life under dynamic loads.
Class 2e: Parts have hardness of Rc 40 or above and are designed for unlimited life under dynamic loads.