Corrosion study of biodiesel with different acidity levels on a microalloyed steel

The production of biodiesel through the transesterification of vegetable oils and fats using homogeneous basic catalysts requires low acidity and moisture raw materials, which increases the cost of production and compromises the viability of the technology. On the other hand, the feasibility of biodiesel production using higher acidity and lowcost raw materials leads to an increase in the process investment cost due to the need to use equipment built with special steels. The objective of this paper is to evaluate the corrosion resistance of a microalloyed steel, a lower cost material when compared to special alloys, in contact with canola biodiesel. In order to investigate the influence of acidity on steel corrosion resistance, pure biodiesel and biodiesel samples with 1, 3 and 10% oleic acid were added. The corrosion resistance of steels was determined using measures of mass loss, corrosion rate and conductivity. The results suggest that canola biodiesel creates a protective layer called biofilm under the microalloyed steel after a time of contact, causing the corrosion to decrease and a reduction in acidity was also observed. After 30 days of contact, a significant increase in corrosion rates can be observed, probably caused by the rupture of the biofilm.