Effects of palm biodiesel and blends of biodiesel with organic acids on metals

This paper presents the corrosion behavior studies of five metallic materials used in auto part manufacturing exposed to pure palm biodiesel (B100) and palm biodiesel mixed with acidic species commonly found in biodiesel. Samples of AISI-SAE 1005 carbon steel, AISI-SAE 304 stainless steel, tin, aluminum and copper were exposed to a temperature of 45 °C for 12 months. The highest corrosion rates were present in totally immersed copper (B100-acetic acid blend) and in carbon steel (B100-oleic acid blend). The most corrosive blends for the metallic materials were B100-linoleic acid, B100-oleic acid and B100-acetic acid. The efficacy of two corrosion inhibitors, ethylenediamine (EDA) and tert-butylamine (TBA) increased as a function of exposure time. The characterization tests allowed the detection of different species, in the products of steel corrosion, associated with, lepidocrocite, ferrihydrite, magnetite, and some iron carbonates. In turn, cuprite, malachite, azurite, and some copper carbonates were found on the copper samples. Such corrosion products formed protective layers on the surface of the metals, which is reflected in a decrease in corrosion rates over time.