Effect of The Free Water Content in Biodiesel On the Corrosion of Copper and AISI 1045 Steel: An Approach Using the Biodiesel/KOH-Solution Interface

Electrochemical measurements in low conductive media, such as biodiesel, are challenging. Here, the electrochemical corrosion process of carbon steel and copper, due to the free water content in biodiesel storage tanks, is studied. The electrochemical analysis was carried out at the interface of the biodiesel and a KOH aqueous solution under controlled experiments that replicate the free water content in biodiesel. The main contribution of this work is a movable working electrode in a typical three-electrode cell configuration for electrochemical characterization purposes. Corrosion of copper and AISI 1045 carbon steel was investigated using three standard electrochemical techniques, open circuit potential, potentiodynamic polarization, and electrochemical impedance spectroscopy. The working electrode was placed on a translation stage provided with a micrometer that allowed measurements at different points of the interface. Copper (4.0 μA·cm2) was found to be more prone to corrosion than carbon steel (0.03 μA·cm2). The results demonstrate that the novel proposed experimental setup provides a reliable option to study the corrosion of metals exposed to biodiesel.