Studies on the Inhibition by Amines Of the Corrosion of Iron By Solutions of High Acidity

The present paper describes studies carried out on the corrosion of both steel strips and iron powder in solutions of 1 normal hydrochloric acid. These studies have been directed toward the evaluation of various aliphatic and aromatic amines as corrosion inhibitors and to the correlation of the structure of the amines with their adsorption characteristics and inhibitor efficiencies. It has been found that the effectiveness of the amines increases with molecular weight in the homologous series and that steric factors which would appear to be more favorable for the adsorption of the amine or its ion at the metal to solution interface increase the inhibition efficiency. These factors are discussed in detail. The series of amines investigated were the aliphatic straight and branched chain, aniline and its homologs, and N-alkylated derivatives, alkylated pyridines and pyridine homologs, and several dibasic aromatic amines.