In the U.S., the Environmental Protection Agency regulates it heavily. įrom a health standpoint, hexavalent chromium is the most toxic form of chromium. To overcome this problem the part may be over-plated and ground to size, or auxiliary anodes may be used around the hard-to-plate areas. ![]() This means it leaves a non-uniform coating, with more on edges and less in inside corners and holes. One functional disadvantage of hexavalent chromium plating is low cathode efficiency, which results in bad throwing power. Finally, the whole bath is agitated to keep the temperature steady and achieve a uniform deposition. Temperature is also dependent on the current density, because a higher current density requires a higher temperature. 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 (CrO 3) and sulfuric acid ( sulfate, SO 4), 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: (1) activation bath, (2) chromium bath, (3) rinse, and (4) rinse. ![]() Hexavalent chromium plating solution is used for decorative and hard plating, along with 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 (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. Disposal of chemicals is regulated in most countries. The chrome plating chemicals are very toxic. Various finishing and buffing processes are used in preparing components for decorative chrome plating. A typical hard chrome vat plates at about 1 mil (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. Application of plating current for the required time to attain the desired thickness.Placement into the chrome plating vat, where it is allowed to warm to solution temperature.Various pretreatments depending on the substrate.Manual cleaning to remove all residual traces of dirt and surface impurities.( April 2021) ( Learn how and when to remove this template message)Ĭhrome plating a component typically includes these stages: Unsourced material may be challenged and removed. Please help improve this section by adding citations to reliable sources.
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