Electrochemical polarization measurements of tooling alloys in pyrolysis oil

Biofuels are more environmental friendly than fossil fuels and can be used in diesel motors and power plants, but the corrosion of materials used for these systems has to be considered. Electrochemical measurements are quick and sensitive ways to investigate corrosion properties of metallic materials, however, the medium should be conductive (i.e., electrolyte) in order to perform such measurements. Pyrolysis oil is one kind of biofuels, which has a high aqueous content, a low pH and a high conductivity, and thus electrochemical measurements are feasible. In this study, cyclic polarization measurements were performed to investigate the corrosion behavior of two nitrogen-based (Vanax 35 and Vanax 75) and one carbon-based (Elmax) tooling alloys in pyrolysis oil, and stainless steel AISI 316L was included for comparison. The samples of the tooling alloys underwent the same heat treatment, including austenitizing, quenching and tempering, to obtain proper mechanical property. The cyclic polarization measurement was performed with a scan rate 100 mV/min. The start potential was -0.2 V vs. OCP, and the final potential was set to the OCP. By an automatic setting in the software, the upward potential scan was reversed when the anodic current density reached at 0.1 mA/cm 2.