Microhardness and roughness in nickel electrodeposition under pulse reversed current conditions

Abstract

The pulse reversed current (PRC) technique perturbs the electrocrystallization process and as a results changes the surface morphology and the properties of the deposits. The effect of this technique on the electrocrystallization mechanism depends, in addition to the other electrolysis conditions, on two new parameters: the pulse frequency v and the duty cycle [ T/( T+ T')] × 100, where T is the deposition time (cathodic period) and T' the dissolution time (anodic period). The purpose of this work was to study the changes in the microhardness and the roughness in correlation with the textural modifications, occuring of nickel deposits prepared from an organic-free Watts-type bath, as a function of the PRC parameters. The microhardness of the deposits was determined by the Vickers method and the roughness by the R a value. It was found that the PRC technique affects the composition of the catholyte with a mechanism analogous to the action of organic additives, by reinforcing the selective adsorption phenomena of the crystal growth, and permits the preparation of smooth and hard nickel electrodeposits in the absence of organic additives.