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.
KEYWORDS: 5xxx aluminum alloys, beta phase, sensitization, ASTM G66, ASTM G67,
electrochemical cyclic polarization, metallographic analysis