CORROSION INHIBITION OF CARBON AND LOW-ALLOY STEELS IN SULFURIC-ACID-SOLUTIONS BY 2-MERCAPTOPYRIMIDINE DERIVATIVES

Several derivatives of 2-mercaptopyrimidine (containing -OH, -SH, -NH2 or -CH3 substituents) have been studied as corrosion inhibitors of AR MCO iron and low alloy steels in 1 m sulphuric acid solutions. Tests h ave been conducted during 6 h in the temperature interval between 60 a nd 90-degrees-C. The trends of the corrosion rates as a function of ti me have been determined by polarisation resistance measurements and an alytical determinations of dissolved iron. 2-mercaptopyrimidine, 2,4-d imercaptopyrimidine and 2-mercapto-4-methylpyrimidine showed the most satisfactory action, reaching efficiencies of 98% on ARMCO iron at 90- degrees-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-degrees-C. A tentative interpretation of the action mechanisms of the additives has been given on the basis of their mole cular characteristics.