Physico-chemical investigation of Rust preventive oil

Abstract

The physico-chemical properties of rust preventive oils were studied in order to resolve the mechanism of rust preventive action and to shorten the timeconsuming tests by using physico-chemical measurements. Good rust preventive oils generally show oriented structures on the metal surface. However, the spot pattern comes from the layer of a high molecular crystalline substance on the surface of the oil film, and it follows that good rust preventive oils fortified with proper additives, do not necessarily show oriented structures. The pulse polarizer method was applied on the iron anode coated with rust preventive oil. It was immersed in 1N potassium chloride solution, and the variation of the anode potential and the impedance of the film were simultaneously observed. The results indicate that a good rust preventive oil can spontaneously restore a breakdown on the film caused by pulse discarge, to its original state and that the film will not be damaged even by repeated pulsation. The surface potential changes in the atmosphere of oxygen or water vapor indicate that ordinary petroleum oils admit the passage of oxygen or water vapor through the oil film, and these gases are adsorbed on the metal surface. On the other hand, rust preventive oils inhibit the adsorption of oxygen or water vapor on the metal surface; thus making it possible to provide good rust preventive properties. The potential change at repeated pulse discharges can well be correlated with the fingerprint removability, while the surface potential changes on the metal, which is coated with a rust preventive, in the water vapor aimosphere can well be correlated with the results of the humidity cabinet test.