Acetylenic alcohols as inhibitors of iron acid corrosion. Improvement of the inhibition efficiency of a class of substances based on their action mechanism

This paper shows the results obtained in “A. Daccò” Corrosion Study Centre on the inhibition of iron acid corrosion by acetylenic alcohols. The improvement in the protective performances of this class of substances was obtained through base molecule modifications related to their action mechanism (i.e., initial adsorption onto the metal surface and successive polymeric layer formation). Therefore, in an attempt to favour molecular adsorption, some 3-methyl-1-butyne derivatives were modified by substituting the acetylenic hydrogen atom with halogen atoms (Cl, Br or I), while alkyn-3-ols were modified by increasing their alkyl chain length to determine the subsequent polymeric layer improvement. The presence of halo-atoms of increasing polarizability favoured the inhibiting action of 3-methyl-1-butyne derivatives to the anodic reaction, while the lengthening of the alkyl chain in alkyn-3-ols promoted a marked increase in the inhibiting effects due to the formation of a thick layer. In this latter class of substances the iodine atom significantly increased the persistence of the inhibiting action.