Investigating the tribochemical behavior of the hard chromium coating deposited via the electroplating method with direct and pulse current on copper substrate

Department of Materials Science and Engineering, College of Chemical and Metallurgical Engineering, Shiraz Branch, Islamic Azad University, Shiraz 71955, Iran
e-mail: m.mansouri.2468@gmail.com

Received: 21 September 2014
Accepted: 28 July 2015

Abstract

Hard chromium coating is a common coating used in industries against environments which are corrosive or show high wear rates. The chromium coating can be applied electrically using direct or pulse current in a sulfate-catalyzed chromic acid bath at a plating current density of 0.16 A cm^-2. In this study the hardness, wear and tribochemical resistance of the chromium coating applied using direct and pulsed current on a copper substrate were compared and investigated. For this purpose, the different coatings (DC and pulse) were analyzed by microhardness evaluation, scanning electron microscope (SEM), energy-dispersive spectroscopy (EDX) and a pin-on-disk wear test. The wear test was performed in dry and wet environments to study the effect of corrosive environments on the wear rate of the coatings. The environments consisted of deionized water with different percentages of sulfuric acid (0%, 5%, 10% and 15% vol.). Moreover, the worn-out surface of the samples was analyzed by SEM and EDX to clarify the wear mechanism. The results show that the wear rate of the chromium coating applied using the pulsed current is higher than the coating applied using the DC current in both wet and dry environments. Moreover, it was clarified that increasing the acid content increases the wear rate, but the predominant mechanism in all of the samples was adhesive wear.