Polarization and Corrosion of Electrogalvanized Steel—Evaluation of Zinc Coatings Obtained from Waste‐Derived Zinc Electrolytes

Abstract

The corrosion of electrogalvanized 1070 steel wire has been investigated in molar quiescent ammonium chloride and ammonium sulfate under near‐neutral conditions. Zinc coatings obtained from waste‐derived electrolytes were evaluatedvs. coatings from relatively pure zinc electrolytes. The waste source of zinc was brass smelter flue dust. Corrosion rates were measured by Tafel line extrapolation and the polarization resistance technique. Values of the Tafel slopes and the corrosion currents were also compared with those for pure zinc (99.999%). Corrosion rates were found to be affected by the medium employed, pH, and bimetal diameter reduction (drawing). Drawn electrogalvanized steel displays higher values of the Tafel slopes than do the as‐plated samples. The Tafel slopes are different from those obtained on pure zinc. This is assumed to be due to inhomogeneous surface features obtained from additive adsorption (during plating) and residual lubricants used in the drawing process as well as surface structure. The corrosion rates of electrogalvanized samples plated in the waste‐derived zinc electrolytes were similar to the corrosion rates of samples plated in relatively pure zinc electrolytes. Therefore, wastes are a potential source of zinc for electrogalvanizing.