AA5456-H116 undergoes accelerated localized corrosion when in a galvanic couple with cupronickel alloy C70600 during ASTM G85 Appendix 2 Wet Bottom (G85 WB) testing. Surface and subsurface damage of AA5456-H116 was investigated and quantified. These results were compared to Finite Element Modeling results investigating relative humidity (RH) and water layer (WL) thickness. The best fit between experimental results and the modeling results was found when modeling assumed that a 3,000 ┬Ám water layer was formed during the spray portion of the G85 cycle with thinner water layers present during the decreasing RH portion of the cycle, which led IGC attack that was focused in the proximity of the CDA/AA5456-H116 interface. The high-water layer thickness is likely the result of the corrosion product formation that traps additional electrolyte than would be present on a clean surface.

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