2009 Volume 95 Issue 9 Pages 640-644
A simple and sensitive method is described for the determination of the mass per unit area of galvanized coatings by differential pulse anodic stripping voltammetry in the presence of iron matrix. The optimized experimental conditions were as follows: Zn2+ in a sample solution (5 mL) containing a 0.07 M nitric acid–0.05 M sulfuric acid mixture at pH 4 was electrodeposited as zinc amalgam in a hanging mercury drop electrode at −1.15 V vs. Ag/AgCl for 2000 s with stirring; the deposits were then anodically stripped in the potential range −1.15 to −0.7 V vs. Ag/AgCl at a scan rate of 30 mV s−1. The interference of the Fe3+ matrix was eliminated by reducing it to Fe2+ with L(+)-ascorbic acid, and the maximum permissible concentration of Fe2+ was up to 1.5 mg mL−1 by the addition of 0.1 M L(+)-ascorbic acid. The calibration (peak height vs. Zn2+ concentration) graph is linear in the concentration range 20 to 2000 ng mL−1 with relative standard deviation of 2.7% for 100 ng mL−1 (n=5). The possible interferences have been evaluated. The proposed method was applied to the determination of the mass per unit area of galvanized coatings with good precision and accuracy.