Effects of NaCl and NH4Cl on the initial atmospheric corrosion of zinc

Effects of NaCl and NH4Cl on the initial atmospheric corrosion of zinc were investigated via quartz crystal microbalance (QCM) in laboratory at 80% RH and 25 °C. The results show that both NaCl and NH4Cl can accelerate the initial atmospheric corrosion of zinc. The combined effect of NaCl and NH4Cl on the corrosion of zinc is greater than that caused by NH4Cl and less than that caused by NaCl. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy and electron dispersion X-ray analysis (SEM/EDAX) were used to characterize the corrosion products of zinc. (NH4)2ZnCl4, Zn5(OH)8Cl2 · H2O and ZnO present on zinc surface in the presence of NH4Cl while Zn5(OH)8Cl2 · H2O and ZnO are the dominant corrosion products on NaCl-treated zinc surface. Probable mechanisms are presented to explain the experimental results.