Erosion-corrosion of mild steel. (2nd Report, Effect of pH and Cl ions)

The effects of pH and Cl ion concentration on erosion-corrosion of mild steel in aqueous solutions were investigated using an impingement jet flow apparatus. It was found that the mass loss in ion-exchange water decreased with jet velocity, and the mass loss in the water with 6.7 ppmCl reached a peak at 0.1 m/s. Such a peak appeared in the case of the other solutions, but the peak value depended on pH, and was absent when pH > 6.5, because the increase of pH suppressed the breakdown effect of the Cl ion. A large number of pits were generated on the mild steel subjected to the solutions with Cl ions, probably because the Cl ions caused breakdown of parts of the protective film.