Inhibitors for Armco iron and ASTM A106 plain steel in hydrofluoric acid

Abstract

Different classes of organic substance (acetylenic derivatives, nitrogen containing additives, and/or sulphur containing additives) were tested as inhibitors for corrosion of ASTM A 106 plain steel and Armco iron in hot diluted hydrofluoric acid solutions. Those additives interacting with the metal surface by chemisorption through available electron lone pairs were the most efficient substances. The best results were obtained with sulphur containing additives; these markedly inhibit the acid attack on both Armco iron and plain steel. Though very efficient, some sulphur containing additives (e.g. phenylthiourea) act as promoters of hydrogen entry into the metal lattice in hydrofluoric acid corrosion: however, others (e.g. dibenzylsulphoxide) can be safely used as inhibitors in this acid solution.