Hot-Dip Tin Coated Sheet Evaluations for Flexible Fuel Tank Applications

Thickly coated hot-dip tin sheet was evaluated in fuel immersion, exterior corrosion, and weldability tests to determine its viability for methanol fuel tank applications. Performance in solutions of pure gasoline and low percentage methanol blends at ambient temperature and 60°C was excellent for hot-dip tin coated steels. However, in high-temperature testing in high methanol fuel blends, hot-dip tin sheet experienced some coating etching that was likely related to the added contaminants of formic acid and chlorides. Regarding exterior atmospheric corrosion protection, tin coatings are not sacrificial to exposed sheet steel, and therefore, tin coated sheet could be expected to provide exterior corrosion protection similar to terne coated sheet at similar coating weights. Tin coatings may require a primer coating for added exterior corrosion protection in fuel tank applications. The manufacturing processes currently used for production of terne fuel tanks can be applied to hot-dip tin coated sheet steels. Tin coated sheet is readily weldable useing resistance spot- and seam-welding processes, providing flow-back protection of areas adjacent to the weld. Formability and drawability are similar to current terne coated sheet.