Study of the performance of films containing rare earth salts as corrosion inhibitors of zinc-iron alloy electroplated steel

Zinc-iron alloy electroplated steel is a material commonly used in the construction industries and automotive. This zinc-based material needs, however, to be protected against corrosive environments through a surface treatment that generally has hexavalent chromium, wich is toxic to the environment and may cause cancer to human being. This paper shows a study with the films of rare earth (Ce or La) on the zinc-iron alloy electroplated steel. These films were evaluated using Polarization Curves, Electrochemical Impedance Spectroscopy (EIS), Scanning Electron Microscopy (SEM) and EDS. The X-ray photoelectron spectroscopy (XPS) was also used to prove the existence of oxide films on the surface of zinc-iron alloy electroplated steel. The EIS and Polarization results have shown that the systems under study were efficient against corrosion and its performance depended upon the type of salt. The sample ZnFe+Ce proved to have the best inhibitors against corrosion. The cathodic branch of the polarization curve presents a decrease in order of 10 times in the current density when the ZnFe alloy coating were treated with rare earth and IZI. increase in order of one time at the same circumstance.