Effects of deposition potentials on the morphology and structure of iron-based films on carbon steel substrate in an alkaline solution

Abstract

The purpose of this work is to investigate the effect of electrochemical deposition potential on the morphology and structure of iron-based films on the carbon steel in an alkaline Fe(III)-triethanolamine solution. The deposition potentials were controlled in the range from -1.05 to -1.23 VSCE for 1800 s at 80°C. Total amount of electric charge for electrodeposition process was increased with increasing deposition potential in negative direction. Pure magnetite films with a columnar and defect-free structure were deposited in the potential range from -1.05 VSCE to -1.11 VSCE. However, petal-like magnetite film containing ferrihydrite and iron was formed at -1.17 VSCE. At more negative potential of -1.23 VSCE, two distinct layers were observed: a porous outer layer containing ferrihydrite and goethite and a compact inner layer consisting of columnar metallic iron. In the potential range from -1.05 to -1.11 VSCE, the pure magnetite films gradually increased the thickness and decreased the surface roughness with an increase of the overpotential. The magnetite film deposited at -1.11 VSCE showed the most thick layer and smooth surface state.