ZINC LAYER CHARACTERIZATION ON GALVANIZED STEEL BY CHEMICAL METHODS

A method has been developed for corrosion product analysis on zinc galvanized steel. Zinc corrosion products are first removed while leaving the underlying metallic zinc unaltered. This method then permits the amount of metallic zinc to be determined by dissolving it, while oxidation compounds at the zinc/iron interface remain unaltered. Zinc corrosion products are dissolved by glycine solution attack (10 minutes at 25-degrees-C) by which zinc corrosion layers of 10 angstrom thickness can be analyzed. The zinc metallic layer is dissolved by electrochemical attack (anodic polarization at -900 mV), which does not alter the corrosion products, if any, at the Zn/steel interface. After metallic zinc dissolution, steel corrosion products can also be chemically analyzed by treating the specimens with a series of suitable solvents (glycine, bromine-methanol) for recovery and characterization of iron oxidation compounds.