Elucidation of the Corrosion Mechanism of Vegetable-Oil-Based Lubricants

In this paper, the corrosion properties of vegetable oils as base oil for industrial lubricants are evaluated by the copper strip corrosion test (ASTM D130) and rust prevention test (ASTM D665). An analysis of possible organic reaction mechanisms leading to corrosion of metals in the absence and presence of oxygen and moisture is presented, when vegetable oils are used as base oils. Corrosion properties of vegetable oil fatty acids, evolved as degradation products, are analyzed using quantum chemical calculations. The popular quantum chemical software SPARTAN 04 (Wavefunction Inc. USA) was used for the studies employing the semi-empirical PM3 method. The calculations were performed in line with similar reported studies used to analyze the corrosion inhibition properties of many nitrogen and sulfur-containing anti-corrosion additives. The corrosion inhibition properties of ZDDP (zinc dialkyldithiophosphate) were compared to other additives using PM3 semi-empirical calculations. Moisture content in vegetable oils is found to be the leading cause of corrosion in vegetable-oil-based lubricants. Control of moisture content and use of additives like ZDDP can be effective in controlling corrosion.