Influence of temperature on intermolecular association of an inhibitor N, N-dimethyl-cetyl-amine with proton donors and on chemisorption of the inhibitor on steel surface were studied. Presence of the intermolecular association was determined by infrared spectra of the proton donors dissolved in carbon tetrachloride solution of the inhibitor at various temperature. Weight losses of mild steel test coupons prefilmed with the inhibitor in the solution with and without the proton donors at various temperature were measured by dipping in uninhibited 5% HCl aqueous solution.
Inhibition efficiencies of the intermolecularly associated inhibitors were lower than those of the unassociated, since an unshared electron-pair which was necessary for chemisorption of the inhibitor on metal surfaces was blocked by hydrogen-bonding. Elevation of temperature was effective for dissociation of these intermolecularly associated inhibitors. Inhibition efficiencies of the associated inhibitors were, therefore, more increasing than those of the unassociated ones with elevation of the filming temperatures. Warming of filming solution was more effective on increase of inhibition efficiencies of the associated inhibitors at their low concentration than those of high concentration because hydrogen bond could more easily be dissociated.
Adsorption of amine-hydrochloride of which unshared electron-pair was occupied with proton was further studied by measurements of inhibition efficiencies of test coupons pre-filmed in some solvents at various temperature.