(Some thought the pass/fail mass loss criterion of<15 mg/cm2 was too severe.) For two years, this Task Group struggled to prepare a test matrix involving selection of suitable sample configurations, exposure conditions and alloy types that would assess the correlation of NAMLT mass loss values to resistance to IGC, Exfoliation and SCC in natural marine environments. 3 In 2005, a Task Group was established jointly under ASTM B07.03 and G01.09 with the purpose of correlating G67 NAMLT mass loss results with performance in natural marine environments. B928 requires producers to certify that their marine alloy products in the -H321 as well as the -H116 temper (2) 2met the resistance to intergranular corrosion (IGC), exfoliation and stress corrosion cracking (SCC) as determined by testing by ASTM G66 (ASSET), ) ASTM G67 Nitric Acid Mass Loss Test (NAMLT) and metallographic examination. Its purpose is to prevent re-occurrence of these failures. 2 A new ASTM Standard, B928, was established in 2004 for marine aluminum alloy. 1 This same problem had been observed 30 years earlier and was well documented. The presence of selective, continuous grain boundary precipitation of the Mg2Al3 phase, which results in intergranular, exfoliation and stress corrosion cracking, was the result of improper metallurgical processing. A field survey and metallographic studies concluded that the cracking was the result of stress corrosion cracking (SCC). In 2000-2001, cracking of 5083-H321 plated structures was detected on several patrol and catamaran ferry boats built in the Pacific Northwest. This led to the ASTM Task Group's current use of a modified perform specimen configuration (U-Bend) for more extensive SC tests of the 5XXX alloys with varying mass loss values.1 atmospheric test of preformed samples of sensitized 5083-H321 in both sheet and plate thicknesses are provided. This paper describes how a preform- stressed specimen configuration was found to serve this purpose. Resistant tempers cited in B928 are -H116 and -H321. (1) The intent of B928 is to prevent use of alloys and tempers that are not resistant to intergranular corrosion, exfoliation and stress corrosion. ASTM B928 was established in 2004, following an inspection survey in 2002 of several boats exhibiting stress corrosion cracking in hull and deck plates of 5083-H321. ASTM Task Group B07.03/G01.09 needed a stress corrosion test specimen for relating nitric acid mass losses (ASTM G67) cited in ASTM B928 to stress corrosion resistance in marine environments.
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