Application of microalloyed steels for handling of acidic chemicals in the biodiesel industry

Base-catalyzed transesterification of vegetable oils and fats is one of the most used technologies for biodiesel production globally. Several alternatives have been studied to enable the use of acidic and cheap raw materials for biodiesel production, but the initial investments are usually high due to the need for equipments made up of special steels. The present work was aimed at evaluating the corrosion resistance of three Brazilian steels in biodiesel with different acidity extents. Biodiesel was synthesized by the transesterification of soybean oil with methanol and further added oleic acid at specific contents. Gravimetric tests were carried out by the immersion of the steels in the biodiesel samples for up to 1344 h. The corrosion resistance of the steels was evaluated by corrosion rate determinations, whereas the biodiesel quality was monitored by acidity index and conductivity measurements. The best results were obtained with the microalloyedsteel, however, the quality of the biodiesel was reduced with the increasing oleic acid content, restricting the application of microalloyed steel to biodiesel with an acidity of up to 1%.