The influence of chromium on the atmospheric corrosion of steel

The corrosion behavior of mild steel and Cr-containing steel has been investigated during wet/dry transitions. The corrosion potential was measured with a Kelvin probe and the corrosion rate was followed by the decay of the partial pressure of oxygen in a closed volume. The corrosion rate during drying was closely correlated with the corrosion potential during the wet period for mild steel: the high corrosion rate during drying was observed, if the surface had been polarized before to negative potentials less than -0.2 V-SHE during the wet corrosion conditions, and only low corrosion rate was observed during the period of drying, if the corrosion potential stayed at a positive potential greater than -0.2 V-SHE during the wet stage. The addition of Cr affected the corrosion not during the wet stage, but during the drying stage greatly, and the low corrosion late was observed during drying even if the surface had been polarized before to negative potentials below -0.2 V-SHE during the wet corrosion conditions For Cr-containing steels. This can be interpreted by the difference of the rust reduction behavior owing to the existence of Cr in the rust layer. The main influence of Cr on the corrosion during wet/dry cycle is presumably, the inhibition of the cathodic reaction. (C) 2001 Elsevier Science Ltd. All rights reserved.