Effect of PEG addition and temperature on hard chromium coating using eco-friendly trivalent chromium

Abstract

Commonly, electro deposition of chromium is carried out by using Chromium trioxide (CrO3) solution. CrO3 contains hexavalent chromium or Cr(VI) ions which is toxic and carcinogenic. Some countries such as Japan, America and the European Union including Indonesia on have banned the use of it as stated in their safety and health regulation. Chromium hexavalent is then replaced by trivalent chromium as it is safer and environmentally friendly. The trivalent hard chromium plating is more difficult to undertake than hexavalent hard chromium plating. In this research the effect of PEG 4000 addition and solution temperature variation was observed to achieve the maximum surface coating hardness. The result of coating was confirmed by using XRD and Optical Microscope. The highest hardness obtained is 957.2 ± 40 HV0.3 at temperature of 45°C with 6 g/l PEG 4000 addition it has also shown a small micro crack observed by Optical microscope. The maximum thickness of 81.3 ± 4.6 µm observed at 60°C with 6 g/l PEG 4000 addition. The diffractogram obtained is a typical of a trivalent chromium coating. Further research will be carried out to have deeper understanding on the behavior of the trivalent hard chromium electroplating.