The inhibition action of four amine compounds (e.g. p-toluidine, o-aminophenol, anthranilic acid and ophenylenediamine) on the corrosion of mild steel in HCl solutions has been studied using weight – loss technique. The
results revealed that most of the amine compounds inhibit the corrosion of mild steel. It is obvious that, at each inhibitor
concentration the inhibition effect for the amine compounds increases in the following order: anthranilic acid > ophenylenediamine > p-toluidine. The inhibition effect of anthranilic acid and o-phenylenediamine compounds could be
attributed to the formation of an insoluble adsorbed complex layer onto the metal surface, while in case of p-toluidine
the inhibition effect was ascribed to the formation of a link between the – NH2 group and the metal surface via
adsorption. On the other hand, different concentrations from o-aminophenol in HCl were found to accelerate corrosion.
This stimulating action towards the corrosion of mild steel could be due to oxidative tendency of the formed adsorbed
surface complex. The corrosion inhibition mechanism is discussed depending on the nature and surface charge of the
metal, the type of the aggressive electrolyte and the chemical structure of the amine compounds.