Initial atmospheric corrosion of zinc in presence of Na2SO4 and (NH4)2SO4

Initial atmospheric corrosion of zinc in the presence of Na2SO4 and (NH4)2SO4 was investigated via quartz crystal microbalance(QCM) in laboratory at relative humidity(RH) of 80% and 25 °C. The results show that both Na2SO4 and (NH4)2SO4 can accelerate the initial atmospheric corrosion of zinc. The combined effect of Na2SO4 and (NH4)2SO4 on the corrosion of zinc is greater than that caused by (NH4)2SO4 and less than that caused by Na2SO4. Fourier transform infrared spectroscopy(FTIR), X-ray diffractometry(XRD) and scanning electron microscopy(SEM) were used to characterize the corrosion products of zinc. (NH4)2Zn(SO4)2, Zn4SO4(OH)6·5H2O and ZnO present on zinc surface in the presence of (NH4)2SO4 while Zn4SO4(OH)6·5H2O and ZnO are the dominant corrosion products on Na2SO4-treated zinc surface. Probable mechanisms are presented to explain the experimental results.