Oil Removal by Alkaline Cleaners.

Abstract

A study of the effect of variations in surface condition on ease of oil removal from metal surfaces has shown that mineral oil is readily removed from cold-rolled surfaces but this removal is sharply diminished after mild pickling operation. Buffing of pickled surfaces or, in the case of steel, passivation with concentrated nitric acid, results in restoration of a high level of cleaning efficiency in mineral oil removal.Removal of this oil is also efficient with steel surfaces covered with oxide (mill scale). This efficiency is greatly reduced on pickling. As the surfaces become rougher, the effects due to pickling and passivation are re-ARECENTLY developed method of evaluating metal cleaners has been applied to a study of the effect of the surface condition of metals on the ease of removal of oils from these surfaces. The importance of maintaining uniform surface conditions in this method was pointed out in a previous description of the method (.5). It was based on the observation that aluminum surfaces with a mirror finish gave high values for cleaning index, which were sharply-reduced upon abrasion with fine steel wool. . This investigation has disclosed that large variations in cleaning efficiency may be observed as a result of changes in surface condition. Therefore, data on this factor should be important in the evaluation and use of alkaline metal cleaners. There is apparently-little literature on this subject, and the relatively complete bibliography-on aluminum metal cleaners of Harris and Mears (2) does not make any reference to this factor.The procedure used here for evaluating the cleaners was similar to that previously reported (5). In general, this consists of coating metal panels by immersion in various oils, followed bydrainage under standard conditions, particularly-with regard to temperature. The panels are cleaned by a controlled procedure in which time, concentration, agitation, and temperature are uniform. After a prescribed rinsing operation, the panels are sprayed with water. This results in a uniform water film over the cleaned areas whereas discrete droplets condense over the areas that have not been thoroughly cleaned.These delineated areas are sketched on graph paper having one hundred squares, and the• percentage of the panel area that has been cleaned is thus estimated. The cleaning index