The effect of various derivatives of polymethylenebis-2,2-benzimidazol
e on the corrosion and electrochemical behavior of steel in H2S-contai
ning acids has been studied. Pentamethylenebis-2,2-benzimidazole appea
red to be the best inhibitor. The test compounds inhibit both electroc
hemical (anodic inhibition) and chemical corrosion. Stress corrosion t
ests also showed the inhibitors to be efficient. Rough estimates sugge
st that the blocking effect dominates over the energetic psi(1) and ki
netic effects in the optimum mechanism of inhibition.