Laboratory Perforation Corrosion Tests of Autobody Steel Sheet

The Corrosion Task Force of the Automotive/Steel Partnership (A/SP) and the Society of Automotive Engineers' Automotive Corrosion and Prevention (SAE/ACAP) committee are working cooperatively on the development of an improved laboratory test for perforation corrosion. This paper gives the results of testing a set of standard SAE perforation corrosion test specimens for up to 160 cycles in the environment of J 2334, the new SAE cyclic test for cosmetic corrosion. SAE J 2334 was found to provide a clear distinction among the test materials. In general, the results indicate that the perforation corrosion resistance of coated products is much greater than that of cold rolled steel, and that it also increases with coating mass, as well as with application of a barrier organic coating. Magnetite (Fe₃O₄) was the predominant iron corrosion product found in the crevices of the perforation corrosion test specimens. Smaller amounts of goethite (α-FeOOH) were also found. Zincite (ZnO) was the only zinc corrosion product found in the crevices of the zinc and zinc-alloy test specimens. These results will be compared to those of on-vehicle tests of identical specimens currently being conducted at St. John's, Newfoundland; Montreal, Quebec; and Detroit, Michigan.