Aluminum 5000 series (5xxx) alloys are commonly used for ship structures. The alloys with greater than three percent Mg have problems with sensitization, collection of the beta-phase (Mg2Al3) at grain boundaries when exposed to elevated temperatures. The corrosion mode of many sensitized alloys is exfoliation, while non-sensitized alloys tend to pit. This study was conducted to find correlation of corrosion mode to electrochemical cyclic polarization data by comparison with ASTM G66 and ASTM G67 accelerated tests data and metallographic analyses. Electrochemical and ASTM G66, G67 results are correlated with the metallographic analyses to assess beta-phase distribution and impact on corrosion mode and extent. Welded material presents the greatest challenge to this endeavor as chemical composition varies across the fusion region and the base metal temper is disrupted in the heat affected zone.

Subject
Marine environments, Water, Materials, Mass loss, Metallography, Base metals, Sensitization, Pitting, Marine vessels, Aluminum alloys, Grain boundary, Alloys, Protection potential
Keywords:
5xxx aluminum alloys, beta phase, sensitization, ASTM G66, ASTM G67, electrochemical cyclic polarization, metallographic analysis
Government work published by the Association for Materials Protection and Performance (AMPP) with permission of the author(s). Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
2009
GOV
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