Abstract
In order to confirm the adsorption of organic corrosion inhibitors on metals by means of back-donation of the metal electrons to an vacant orbital of the inhibitor, the inhibition efficiency of electron-accepting inhibitors was determined for pure iron in a 6.1M HCl solution by polarization measurements. Nitrobenzene derivatives were used as the electron-cacepting inhibitors. They accelerated the cathodic reaction because of their reduction, whereas they inhibited the anodic reaction. The inhibition efficiency of these inhibitors for the anodic reaction was expressed by the Hammett-like equation associated with the Hammett constant, σ. The efficiency of the compounds with an electron-attracting substituent (σ>0) increased with a decrease in the electron density of the nitro group. Since the efficiency of these compounds was closely related to the half-wave potential of reduction, the back-donation of metal electrons to the antibonding π-orbitals was concluded to play an important role in the adsorption of the nitrobenzene derivatives on the iron surface.
