The Impact upon Applicability of Metal Fuel Tank Using Different Biodiesel

With the development of world economy, the shortage in the supply of oil energy as well as the greenhouse effect have become a public concern around the world. The application of biodiesel on vehicle transportation has become the focus of development in many countries. Biodiesel, Fatty Acid Methyl Esters (FAME), is made during the process of transesterification of the animal and vegetable oils. Compared with fossil diesel, biodiesel has some characteristics, such as organic acid, higher water saturation, and oxygen content. From the results of the literatures [1] to [5], it showed that biodiesel would cause the inflation of some plastic and flexible products and the corrosion of metal materials.

Metal fuel tanks have the characteristics of high flammability, high impact resistance, and good workability and are often used in commercial vehicles. The corrosion of metal materials is a natural chemical change and it can be influenced by the environment. The metal materials soaked in biodiesel will show different rates of corrosion and phenomenon, influenced by the factors such as water content, PH value, dissolved oxygen, temperature, conductivity, microorganism attachment and so on. Therefore, nine different oils (D100, B2, B5, B10, B20, B40, B60, B80, and B100) and four different samples of metal fuel tanks (Zn, ZnSn, SUS 304 and SUS 316) were used in this study under the conditions of room temperature, and high humidity. With the samples soaked for 2400 hours, the visual investigation was used for surface observation, the film thickness gauge was used to measure the thickness of Zn coating, SEM & EDS qualitative analysis were conducted, and the conductivity of the oils was analyzed periodically to study the impacts of biodiesel on fuel tanks.

The results of this study showed that after being soaked for 2400 hours, on the surfaces of the four different metal fuel tank samples, rust or corrosion were not found. There were some color changes found on the Zn coated samples soaked in B40 and above, but the thickness of Zn coating was not reduced. Using the SEM & EDS element analysis, it was found that there was some oxidization on the Zn coated samples with the increase of the percentage of the biodiesel. As for the stainless steel samples, little oxygen was measured. However, for the quality of biodiesel, the performances on conductivity, oxidation stability and the amount of dissolved Zn from the Zn coated samples using high percentage biodiesel (B20 and above) were poor. If the fuel tank was made of Zn coated material, it might increase the deterioration of high percentage biodiesel. Therefore, it is suggested that when using or transporting low percentage biodiesel (B20 and below), the material of the equipment should be coated with Zn or stainless steel. However, when storing high percentage biodiesel for long hours, the storage equipment should be made of stainless steel to avoid speeding the deterioration of the quality of the oils.