Influence of pH on corrosion behavior of carbon steel in simulated cooling water containing scale and corrosion inhibitors

In this paper, the influence of pH on the corrosion behavior of AISI 1020 carbon steel in simulated cooling water was investigated by using electrochemical and surface analysis methods. The results of polarization showed that the corrosion resistance of carbon steel increased with an increase in pH of the simulated water, and the corrosion control process changed from cathodic polarization to anode polarization control. The scale and corrosion inhibitor 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA) had a certain anodic corrosion inhibition effect on carbon steel, whereas Zn2+ acted as a cathodic inhibitor for carbon steel in simulated water with pH 7-9. In simulated water containing both PBTCA and Zn2+, a good synergistic corrosion inhibition was found between PBTCA and Zn2+, and their corrosion inhibition effect on carbon steel was the best at pH 8. This was attributed to the formation of Zn(OH)(2) precipitate film in the cathode region and the formation of Zn-PBTCA complex film in the anode region at this pH.