2011 Volume 60 Issue 7 Pages 333-341
Corrosion rate of steel is controlled by oxygen diffusion through in a 10-100 μm electrolyte film. If the electrolyte thickness decreased to less than 10 μm, oxygen dissolution rate controls the corrosion rate. We developed a numerical analysis model for galvanic corrosion under a thin electrolyte film in consideration of oxygen dissolution rate and diffusion rate. In this model, oxygen salting-out effect, thermal dependence of electric conductivity and oxygen solubility were also considered. NaCl solution salt spray test (SST) and cyclic corrosion test (CCT) were conducted on Fe/Zn galvanic electrode and galvanic current was measured to compare with the numerical results. The galvanic current showed its maximum value during wetting and drying process. The galvanic current calculated by this model agreed with the SST and CCT results. In addition, the electrolyte thickness in the CCT was estimated by numerical analysis model, it is indicated that galvanic current becomes maximum value when the electrolyte thickness is 3-10 μm.