Tribological and electrochemical behavior of thick Cr-C alloy coatings electrodeposited in trivalent chromium bath as an alternative to conventional Cr coatings

Alternative process to hexavalent chromium plating, substitute materials and new designs are urgently needed owing to the requirement of “clean” manufacture. This comparative study was conducted to systematically investigate the tribological and electrochemical behavior of the Cr-C alloy coatings electrodeposited from a trivalent chromium bath and the hard Cr coatings electrodeposited from conventional hexavalent chromium bath, using reciprocating ball-on-disc tribometer and electrochemical analyzer. The electroplated Cr-C alloy coatings with thickness of 50 μm and acceptable quality that can be used for wear resistance as well as corrosion resistance purposes were produced successfully. The results show that the as-deposited Cr-C alloy coatings exhibited crack-free surface and amorphous/microcrystalline structure. The following heat treatment resulted in the cracked surface and the increase in hardness for the electroplated Cr-C alloy coatings. In contrast, the conventional Cr coatings exhibited cracked surface and their hardness decreased with the increase in annealing temperature. The electroplated Cr-C alloy coatings after heat treatment at 200 °C for 1 h exhibited better wear resistance than the conventional Cr coatings. In regard to the electrochemical behavior, the as-deposited Cr-C alloy coatings exhibited better corrosion resistance than the conventional Cr coatings. Therefore, the electroplated Cr-C alloy coatings are environmentally acceptable candidates to replace the conventional Cr coatings.