Effect of Polymer Systems Having Carboxyl Groups as Corrosion Inhibitors in Cooling Water Systems

Relationship between Molecular Structure and Corrosion Inhibition Capability

Abstract

We investigated the effect of polymer systems having carboxyl groups as corrosion inhibitors on the corrosion of mild steel in cooling water systems We found that a ternary copolymer composed of acrylic acid (AA), acrylamide (AAm) and acryloylmorpholine (AMo) was a good corrosion inhibitor Its maximum inhibition efficiency was more than 90%, and formation of scale was limited by an addition of the copolymer in a solution with high concentrations of ionic species For this copolymer system, in the relationship between molecular structure and corrosion inhibition capability, essential factors were that i) the number average molecular weight was about 7×10³ to 1×10⁴, ii) the content of AA was about 70mol%, iii) the bond-structure of carboxyl group to polymer main chain was a direct one, and iv) the functional groups except for the carboxyl group were AAm and AMo A ternary copolymer having these characteristics is potentially an effective inhibitor of corrosion of mild steel.