Influence of corrosion and surface roughness on wettability of ASTM A36 steels

This study aims at investigating the influence of corrosion on water wettability of ASTM A36 steel. To this end, ASTM A36 steel specimens are subjected to different corrosion durations and water wettability of these specimens is determined using contact angle tests based on sessile drop method. Water wettability is found to increase with increase in corrosion of ASTM A36 steels. Pitting corrosion associated with higher corrosion exposure is observed to increase the surface roughness and the subsequent non-uniformity of the corroded surfaces. The increase in the surface roughness due to corrosion is hypothesized as the reason behind the increase of water wettability in corroded specimens. In order to prove this hypothesis, different set of specimens are grinded and polished to achieve a range of surface roughness values. When contact angle tests are conducted on these specimens, it is observed that increase in surface roughness results in increase in the wettability of steel proving the above stated hypothesis. The converse of the hypothesis is also verified by exposing specimens with different surface roughness values to corrosive environment. From a visual examination, specimens with higher roughness values exhibited more corrosion when compared to smoother specimens when exposed to a corrosive environment for same duration. Finally, predictive equations are proposed to estimate the water contact angle of ASTM A36 as a function of surface roughness.