External Corrosion Resistance and Internal Fuel Compatibility of Prepainted Zinc-Nickel for Fuel Tank Applications

Alternative materials to the present terne (hot-dip lead-tin) coated steel are required for fuel tank compatibility with future flexible fuel blends of methanol and gasoline. In addition, the alternative materials must be more resistant to external corrosion from road salts than the present terne coated steel. The goal of the study described in this paper was to identify a coated steel that will satisfy these requirements.

Materials evaluated included organic coatings over terne, galvanneal, and zinc-nickel coated sheet steels. The fuel resistance of these materials was evaluated by exposure to various flex fuel blends at elevated temperature. The external corrosion performance of these coatings was examined by exposure to salt spray and cyclic corrosion laboratory tests. The results of these tests are described in terms of resistance to paint delamination, red rust formation at scribes, cut edges, and deformed areas. The analysis of these test results indicates that electroplated zinc-nickel with an aluminum-rich epoxy paint provides the best overall interior and exterior performance.