Anti-scale performance degradation of carboxylic acid scale inhibitors under corrosion conditions

The anti-scale performance of two typical carboxylic acid scale inhibitors, hydrolyzed polymaleic anhydride (HPMA) and polyaspartic acid (PASP), was investigated under different corrosion conditions of carbon steel. It reveals that steel corrosion induces the anti-scale performance degradation of the carboxylic acid scale inhibitors at steel-water interface, due to the preferential chelation of Fe2+ and carboxylic acid group. The anti-scale performance of scale inhibitor can be fully exerted when corrosion processes are inhibited. Otherwise, uninhibited cathodic oxygen reduction and anodic iron oxidation will induce interfacial pH rising and chelated Ca2+ being replaced, respectively, leading to CaCO3 deposition on steel surface.