Characterization of chrome layer formed by pulse plating

Characterization of thin chrome layers prepared under various pulse plating conditions were systematically studied to improve their mechanical properties. The chrome was electro-deposited from an electrolyte bath containing 500 g l−1 of chromic acid, 10 g l−1 of sulfuric acid using direct current density of 1.6 mA mm−2 and pulse currents with on–off time from 5 to 900 ms. The higher current density enhanced nucleation rate which resulted in refining grain size. The chrome growth kinetics determining nodule size and shape significantly depends on the duration of on-time rather than duration of off-time and on/off time ratio. Microstructural observation by TEM and micro-hardness measurement revealed that the reduction of wear resistance of the chrome deposited by pulse plating resulted from the grain size and residual stress relief during off-time.