Abstract
The effect of phthalic acid, salicylic acid, benzoic acid, o-aminobenzoic acid, and oxalic acid on pitting corrosion of carbon steel in a 0.01 M NaOH solution in the presence of NaCl is evaluated using potentiodynamic anodic and cathodic polarization measurements. The results show that the carboxylic acids shift the pitting corrosion potential toward more positive values, indicating that they have an inhibiting effect. Of the studied acids, phthalic acid has the greatest inhibiting effect and oxalic acid has the lowest inhibiting effect. All the carboxylic acids are mixed corrosion inhibitors, with predominantly anodic inhibition. We discuss the pitting corrosion inhibition mechanism, taking into account the structure of the acid molecules, their behavior in alkaline medium, and the electron density on the COO- group.