The inhibitive properties of amine-₁₈C fatty acid salts against the corrosion of iron in 0.5 M Na₂SO₄ have been evaluated. Potentiostatic polarization and resistance measurements in conjunction with corrosion rate determination indicated a substantial difference between the mechanism and efficiency of action of these compounds in neutral and acidic media. On the ground of previous findings the inferior inhibition in neutral media was linked to the tendency of amines and fatty acids to form complexes which did not lead to such effective surface layers as in acidic solutions. -- AATA