![]() For decorative coating the temperature ranges from 35 to 45 ☌ (100 to 110 ☏), but for hard coating it ranges from 50 to 65 ☌ (120 to 150 ☏). The temperature and current density in the bath affect the brightness and final coverage. This results in an extremely acidic bath (pH 0). The chromium bath is a mixture of chromium trioxide and sulfuric acid, the ratio of which varies greatly between 75:1 to 250:1 by weight. In some cases, the activation step is done in the chromium bath. This etches the work-piece surface and removes any scale. The activation bath is typically a tank of chromic acid with a reverse current run through it. Ī typical hexavalent chromium plating process is: Hexavalent chromium plating solution is used for both decorative and hard plating, as well as bright dipping of copper alloys, chromic acid anodizing, and chromate conversion coating. Hexavalent chromium plating, also known as hex-chrome, Cr 6+, and chrome (VI) plating, uses chromium trioxide (CrO 3, also known as chromic anhydride) as the main ingredient. Some common industry specifications governing the chrome plating process are AMS 2460, AMS 2406, and MIL-STD-1501. A typical hard chrome vat plates at about 0.001 inches (25 μm) per hour. Sometimes the component has a conforming anode made from lead/tin or platinized titanium. Sometimes the component enters the chrome plating vat while electrically live. Ferric chloride is also popular for the etching of nimonic alloys. ![]() Different substrates need different etching solutions, such as hydrochloric, hydrofluoric, and sulfuric acids. There are many variations to this process, depending on the type of substrate being plated.
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