Effect of Sulfonate Ratio of Acrylic Acid Co-polymer on Corrosion Inhibition in Cooling Water Condition

摘要

The acrylic acid polymer is one of the important substances for cooling water treatment to inhibit scaling of minerals and corrosion inhibitor such as phosphate and/or zinc compounds, but the relationship between polymer composition and corrosion inhibition effect has not been well clarified yet. The corrosion study of co-polymers of acrylic acid and sulfonated monomer at different monomer ratios with and without phosphate and zinc corrosion inhibitor showed that there were optimal sulfonate-monomer ratios at different calcium hardness for corrosion inhibition of carbon steel. The in-situ and ex-situ surface analysis were conducted to observe the influence of polymer composition on formed rust on the carbon steel in cooling water condition. The in-situ observation of rust by X-ray computed tomography (X-ray CT) scan showed that the rust formed on carbon steel with sulfonated co-polymer for reducing corrosion rate was denser than that with not-sulfonated polymer. The ex-situ observation of rust by EPMA showed that more concentrated phosphorus and zinc were observed at optimal sulfonated ratio of co-polymer in phosphate-zinc based treatment. These results indicate that sulfo group in the polymer for cooling water treatment has important roles not only in scale inhibition but also in corrosion inhibition of carbon steel by affecting the characteristics of rust formed.