Macro-cathodic Reaction Efficiency of Low Alloy Steels in Sea Water

Yoshiaki Shimizu, Akihiro Tamada, Iwao Matsushima
1978 Corrosion engineering digest  
The corrosion resistance of low alloy steels have been studied with particular attention to the formation of macro-cathodic area on the corroded surface. Additions of chromium to steel increase the macro-cathodic area, which effectively decreases the corrosion rate. The latter behavior cannot be explained by the "catehment area principle" which claims that the corrosion rate is constant as far as the total area for oxygen reduction remains the same. The results of polarization measurements and
more » ... n measurements and various corrosion tests using artificial macro-cathode show that Ca++ and Mg+ ions in sea water deposit on the macro-cathodic area forming an effective oxygen diffusion barrier. Thus, the beneficial effect of macro-cathodic area can be attributed to the slower oxygen reduction on such areas, the increase of which by chromium additions accordingly reduces corrosion.
doi:10.3323/jcorr1974.27.5_229 fatcat:7k3m4tr6dnatxjercqz5e5zf54