Influence of Fatty Acid Methyl Ester Composition, Acid Value, and Water Content on Metallic Copper Corrosion Caused by Biodiesel

Oxidative stability parameters (OSP). acid value (AV), water content (W), and the metallic copper corrosion rate in biodiesels obtained from eight different vegetable oils were determined. Simple and multiple linear regression models were constructed to explain the influence of the OSP, AV and W variables on the corrosion rate. The corrosion rate was lower in biodiesel with less oxidative stability because, instead of reacting with copper, O-2 reacted preferentially with the unsaturated fatty acid methyl esters (FAME) that could act as "sacrificial molecules" to protect the copper against corrosion. Therefore, the corrosion rate was strongly related to the FAME composition. The AV was an important parameter in the corrosion process because free acids react with passivating agents. increasing the corrosion rate. The predictive capacity of W for corrosion rate was statistically insignificant, although water condensed on a copper surface causes corrosion.