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Lubricating oil additives are expected to perform in the presence of polar organic compounds in functioning lubrication system. The present study deals with the influence of polar solvent on the adsorption phenomena of DNNS and other additives on metal surfaces using ellipsometry. The results show that BaDNNS film adsorbed on gold surface from n-hexane solution is not easily desorbed with n-hexane, whereas the film is desorbed with acetone. The same result was obtained with CaDNNS; succinimide dispersant is not easily desorbed by acetone rinse. The same tendency was obtained with chromium, and iron alloy. On the other hand, when Ba-DNNS is adsorbed from acetone solution on gold surface, the adsorbed film consists of two layers, that is, one is easily desorbed with acetone and the other is not. The contact angle measurement suggests that the adsorbed film of BaDNNS from n-hexane solution is different from that for acetone in orientation. The adsorption behavior of BaDNNS on gold from mixed n-hexane/ 1-propanol solution is different from that on carbon black.

The adsorption of alkaline-earth metal salts of dinonyl-naphthalene sulfonic acid(DNNS) on carbon black was studied in a three-component system consisting of Solvent I (n-heptane), Solvent II (polar compounds and others), and DNNS in which the influence of Solvent II was investigated.The adsorption of DNNS is influenced by the kind of Solvent II used. The amount of adsorbed DNNS on carbon black decreases sharply with increasing amount of polar solvent, particularly, in the range of low fractions of the solvent. Non-polar solvents exert mild degrees of influence. Similar phenomenon was observed in the actual diesel engine sludge. There is a trend in the influence on adsorption of BaDNNS by polarity and by solubility parameters of the solvent II used. An isotherm equation for competitive adsorption was derived from the equilibrium theory and found that it was applicable to the data obtained in the present three-component system. Dispersancy of carbon black particle correlates with the amount of adsorbed BaDNNS at low concentrations of 1-propanol.