Tribocorrosion behavior of Zn, Zn-Ni, Cd and Cd-Ti electrodeposited on low carbon steel substrates

The tribocorrosion behavior of electrodeposited Zn-Ni alloy coatings was investigated with a view to assessing their suitability to replace Zn, Cd and Cd-Ti coatings. A modified pin on flat tribometer in an electrochemical cell was utilized to understand wear induced corrosion of the coatings in 3.5% NaCl solution. Wear tests were conducted at open circuit potentials, and impressed anodic potentials of the coatings to determine the corrosion resistance of coatings before, during and after the wear test. Electrochemical impedance spectroscopy was utilized to understand the polarization resistance of the coatings before and after the wear tests. Wear tracks were analyzed with SEM and XRD to determine the nature of corrosion products and surface morphology changes during the tribocorrosion tests. Zn-Ni coatings had higher polarization resistance after wear test as compared to zinc and cadmium coatings. The mass loss due to wear enhanced corrosion was less with Zn-Ni than with Zn and Cd coatings. Zn-Ni coatings are a suitable replacement to Cd coatings when the surfaces are subjected to simultaneous wear and corrosion.