STRUCTURE OF AMINES AND THEIR INHIBITIVE ACTION ON CORROSION OF 63CU-37ZN IN HNO

Aniline, o-chloroaniline, o-nitroaniline, o-anisidine, o-phenetidine, o-toluidine and anthranilic acid have been investigated as inhibitors of the corrosion of 63Cu-37Zn in 2-4N HNO3. Of the substances investigated, anthranilic acid is the most satisfactory inhibitor. Substitution of the ortho position of aniline by electronegative groups such as-Cl,-COOH,-NO2 is beneficial to inhibitor action. The chloro, nitro and carboxyl substituents increase the velocity of diazotization in the ascending order Cl < COOH < NO2 which is in good agreement with the order of efficiency shown by ortho amines having these substituents, namely, o-nitroaniline > o-aminobenzoic acid >o-chloroaniline. However, the diazotization velocities of aniline, o-anisidine, o-phenetidine and o-toluidine are nearly identical but there is a difference in their inhibitor action and hence diazotization of amine and the consequent removal of nitrous acid does not seem to be the only reason of the retarding capacity of the amines. Probably, adsorption characteristics of amines on metal surface also play a significant role in inhibition. © 1969 Pergamon Press.