Galvanically Induced Intergranular Corrosion of AA5083-H131 Under Atmospheric Exposure Conditions: Part 1-Experimental Characterization

In a two-part series of papers, the galvanic corrosion behavior of sensitized aluminum alloy (AA)5083-H131 (UNS A95083) when coupled with AISI 4340 (UNS G43400) steel was studied experimentally and computationally, with an emphasis on atmospheric conditions. In Part 1, the electrochemical kinetics of AA5083-H131 and steel in salt solutions of relevance to atmospheric corrosion were determined, including the influence of the degree of sensitization (DoS), potential, and sodium chloride (NaCl) concentration in the context of intergranular corrosion (IGC) propagation. More severe IGC was seen on materials with higher degrees of DoS, with damage depths of 1 mm or more developing in 100 h. The extent of IGC damage over 100 h was proportional to potential for a wide range of NaCl concentrations. These results from full immersion were compared with exposure testing and scanning Kelvin probe (SKP) measurements conducted under atmospheric conditions. It was found that the extent and spatial distribution of IGC damage on the atmospherically exposed material corresponded well to the IGC damage distribution expected from the SKP potential measurements and the damage results from the full immersion experiments. These findings are used as the input data for the computational model to predict the IGC damage distribution presented in the second paper.