47 Dissolution and Hydrogen Diffusion Control of IGSCC in Sensitized Aluminum-Magnesium Alloys

Prior research affirmed that the mechanism for intergranular SCC in sensitized Al-Mg alloys in chloride solution requires dissolution of grain boundary β to promote severe crack tip acidification, hydrogen production, and process zone embrittlement. This study establishes two new findings that strengthen this mechanism. First, H precharged-notched specimens of alloy 5083 exhibit grain boundary embrittlement, with or without β. Second, extra-ordinarily high rates of IGSCC are enabled by H diffusion, provided that diffusivity is on the order of 10^-7 cm²/s and not reduced by H trapping. Grain boundary embrittlement by precharged H may provide a means to characterize β size and morphology.