Effect of Amines on Polarization of Iron Electrodes

Abstract

An apparatus has been designed and constructed which gives a measure of the effect of organic amine salts on the polarization of iron cathodes in 1.0N sulfuric acid solution. The apparatus consists essentially of a Wheatstone Bridge circuit in which two of the ratio arms are electrolysis cells with a common anode and separate iron cathodes. The elements of the bridge are arranged in such a way that the electrolysis currents through the two cathodes can be measured simultaneously when the cathodes are at the same potential.The effect of the amine salts on the polarization of the iron cathodes has been interpreted in terms of the apparent area changes brought about by adsorption of the amines on the surface of the cathodes. These apparent area changes have then been compared with the per cent inhibitor efficiencies of the amines, as measured by corrosion rate studies. Over the concentration ranges employed, the per cent inhibitor efficiency for each amine is a linear function of the apparent per cent surface area masked by that amine. Since the different amines showed considerable specificity in the relationship between per cent efficiency and apparent per cent area masked, it is concluded that the action of the amine as a corrosion inhibitor is more than a simple masking of certain portions of the surface of the corroding metal.