Corrosion Inhibition in HCl Using Methyl Pyridines

The inhibiting effect of pyridine and seven of its methyl derivatives on the corrosion of iron in O 2 ‐free, at 35°C was determined. Corrosion rates were measured by colorimetric analysis for iron with mercaptoacetic acid. The relative inhibitor efficiency and cathodic potential shift increased with increasing inhibitor concentration and, for a given concentration, with increasing electron density at the nitrogen atom. Both increased slightly with decreasing concentration, but a temperature increase of 10°C had no effect on either. The proposition that chemisorption is involved in corrosion inhibition is supported by these experiments. As a supplementary item the great importance of careful purification of the organic compounds used in such researches as this is documented.