Some process serial may become the obstacle on getting perfect product. There are many variation for this process depending on the type of substrate being plated upon. Different etching solutions are used for different substrates. Hydrochroric, hydrofluoric and sulfuric acids can used. A typical hard chrome vat will plate at about 25 micrometers per hour.
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.
The typical of hexavalent chromium plating process are as follows:
- Activation bath
- Chromium bath
The activation means use chromic acid with a reverse current run through it, this will etches the workpiece surface and removes any scale on the metal surface. The chromium bath is a mixture of chromic acid and sulfuric acid that use the ratio between 75:1 to 250:1 by weight. The temperature and current density in the bath effect the brightness and final coverage. For decorative coating the temperature range from 95 to 115 oF (35 to 46 oC), for hard coating it ranges from 120 to 150 oF (49 to 66 oC). While temperature also dependent on current density, higher current density will require a higher temperature. The whole bath should be agitated to keep the temperature steady and increase a uniform deposition. The next article is how hexavalent component can affect to the chromium plating product.