Corrosion inhibition of carbon and low alloy steels in sulphuric acid solutions by 2‐mercaptopyrimidine derivatives

Abstract

Abstract Several derivatives of 2‐mercaptopyrimidine (containing ‐OH, ‐SH, ‐NH 2 or ‐CH 3 substituents) have been studied as corrosion inhibitors of ARMCO iron and low alloy steels in 1 M sulphuric acid solutions. Tests have been conducted during 6 h in the temperature interval between 60 and 90°C. The trends of the corrosion rates as a function of time have been determined by polarisation resistance measurements and analytical determinations of dissolved iron. 2‐mercaptopyrimidine, 2,4‐dimercaptopyrimidine and 2‐mercap‐to‐4‐methylpyrimidine showed the most satisfactory action, reaching efficiencies of 98% on ARMCO iron at 90°C. The presence of Cr and Mo in the alloys exerted a negative influence on the efficiency of pyrimidine derivatives, by diminishing their action at 90°C. A tentative interpretation of the action mechanisms of the additives has been given on the basis of their molecular characteristics.