Abstract
The diffusion coefficient of oxygen through paint film coated onto mild steel was measured in 3wt% sodium chloride solution and the effect of oxygen on corrosion behavior of coated steel was investigated.
Results in this work were (I) The diffusion coefficient of oxygen through paint film was obtained from measuring a time lag of potential change which occurred soon after aerating a deaerated solution. That of epoxy paint film was 1.1×10-7 to 1.6×10-7cm2·sec-1., (II) The amount of oxygen used for cathodic reaction was calculated from the difference between corrosion currents under aeration and deaeration. The amount of oxygen exhausted was much less than the amount of oxygen permeated which was reported by other workers and it increased with immersion service period., and (III) It was found that the corrosion behavior was affected by oxide film formed at the surface of mild steel under paint film. It was suggested that passivated film was formed at the surface of mild steel under film in the presence of enough amount of oxygen.
