Texture and Surface Morphology Development in Zinc and Zinc-Cobalt Electrodeposits

Abstract

The morphology and texture formation in zinc and zinc-cobalt coatings, electrodeposited onto low carbon steel substrate in an acidic sulfate bath, was studied. The predominant texture component of zinc coating at low current density was pyramidal {11.5} and {11.6} nonfiber, while, for zinc-cobalt deposition, a nonfiber {11.0} prism was found as the predominant texture component. Hydrogen adsorption, during the zinc electrodeposition process, inhibited lateral bunching growth and produced a low-angle pyramidal texture component, which developed ridge morphology. Adsorption of cobalt or cobalt-containing species was the reason for promoting a “field-oriented texture”–type growth in zinc-cobalt deposition, which resulted in a coating morphology, consisting of numerous fibers grown almost normal to the substrate surface. At higher overpotentials, the adsorption was hindered. This led to the progression of lateral growth and the development of a sharp (00.2) fiber texture component in zinc and zinc-cobalt electrodeposits.