Effect of temperature on pulsed current chromium electrodeposition from Cr(III) aqueous solutions

Chromium electrodeposition is widely used industrially to obtain protective coatings with high corrosion resistance combined with other important properties such as high hardness and wear resistance (hard chromium plating) or high surface finishing (decorative chromium plating).In recent years, much attention was given to finding alternative electroplating methods that could achieve similar coatings without the use of hexavalent chromium, given the known toxicity of its compounds. Ideally the deposition of metallic chromium from trivalent chromium acqueous solutions represent the easier strategy to obtain such coatings without the use of hazardous solutions; unfortunatelly a lot of complications concerning the chemistry of trivalent chromium in acqueous solution make this way very difficult to pursue. In this work some deposition strategies have been developed, obtaining; on carbon steel substrate, metallic chromium coatings with good properties (high adhesion to the substrate, micro-hardness, surface finishing) starting from aqueous solutions of Cr (III) and formic acid. The developed strategies are based on the use of pulsed current (and optimization of its process parameters, such as duty cycle, period and magnitude of current applied) and low temperatures.