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The use of tailored-blanks is increasing in the automotive industry as manufacturers attempt to join dissimilar steel grades and thicknesses for parts consolidation and vehicle weight savings. Two methods, laser welding in a square-butt joint and resistance mash-seam welding of overlapped edges, have been used for select applications. Several automotive grade coated sheet steels were laser and mash-seam welded and evaluated for weld integrity, formability, and corrosion resistance. Salt spray and cyclic laboratory tests, and on-vehicle exposures were used for corrosion resistance evaluations. Regarding the corrosion performance of welded parts, it was observed that the weld area provided the weakest corrosion resistance on any given panel. The corrosion performance was, in part, a function of the width of the weld fusion zone.

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 American Iron and Steel Institute's (AISI) Task Force on Automotive Corrosion is making significant progress in its continuing efforts towards development of an accelerated laboratory test for ranking the cosmetic corrosion resistance of automotive steel sheet products. This paper provides an overview of this work and reviews major accomplishments to date. Accelerated tests conducted by the AISI and by the SAE's Automotive and Corrosion Prevention Committee (ACAP) Division 3 are compared to long-term on-vehicle exposure tests now in progress for four years in Montreal, Quebec and St. John's Newfoundland. A license-plate exposure test has also been initiated to broaden the basis for real-world performance. Statistical methods for comparing the results of the various tests are described. A designed experiment (Plackett-Burman L8) is underway to evaluate the effects of seven key cycle test parameters on the rankings of the test materials in a laboratory cyclic corrosion test.

The process considerations, manufacturability, corrosion properties, paintability, weldability, and formability of nominal 9 to 15 percent electrodeposited zinc-nickel (Zn-Ni) alloy-coated sheet steels for automotive applications were reviewed. Zn-Ni coatings were selected for use in automobile body panels by several automakers because of their ease of manufacturing, forming, and welding. Although Zn-Ni coatings may be easily manufactured into autobody panels without a change in production procedures, these coatings exhibit poor paintability and poor corrosion resistance, and would be risky to expose in the U.S. automotive environment at the specified 20 to 40 g/m2 coating weights. Zn-Ni coatings will not provide the cosmetic corrosion protection of zinc or zinc-iron (Zn-Fe) coatings, particularly on exterior autobody panels in a fully painted condition.