1996 Volume 45 Issue 8 Pages 473-479
Invesigated was corrosion behavior of Zn and Zn-Fe alloy electroplated steel sheets in modified Volvo test (atmospheric exposure test with 5%NaCl solution sprinkling). 1) Zn-15% Fe exhibited the best corrosion resistance in the exposure test. 2) It was considered that the excellent corrosion resistance of Zn-15%Fe alloy resulted from the effect of suppresion of oxygen diffusion caused by high coverage of zinc corrosion products and low concentration of iron corrosion products in the corrosion products. 3) As to zinc corrosion products of Zn-15%Fe alloy, it was supposed that 4ZnO·CO2·4H2O existed in the outermost layer, Zn (OH)2 was located in the outer layer, ZnCl2·4Zn (OH)2 or ZnCl2·4Zn (OH)2+ZnCl2 existed in the inner layer in which Zn-Fe alloy coexisted. Iron corrosion products coexisted in the corrosion product layers described above. 4) EG (Zn) corroded ununiformly and formed zinc corrosion products composed of 4ZnO·CO2·4H2O, ZnCl2·4Zn(OH)2 and ZnO with low coverage, and the low coverage decreased the suppressing effect of the products on oxygen diffusion.