Intergranular corrosion prevention of a severely sensitized Al-Mg alloy using additively manufactured surface arrays of zinc island and AM engineered local substrate mixing

RIP2025-00092: The marine grade alloy AA5456 is inherently susceptible to corrosion due to its composition, aging process, and environmental conditions. This vulnerability primarily stems from anodic β-phase precipitates and more cathodic intermetallic particles (IMPs), which act as driving forces for corrosion due to their micro-galvanic couple potential difference. To address this challenge, a novel additive manufacturing approach utilizing "sacrificial anodic zinc lines and islands" was developed, departing from traditional protective barrier coatings that isolate materials. The innovative solution employs Laser Powder Bed Fusion (LPBF) to laser-printed high-purity Zn onto the AA5456 surface, creating sacrificial arrays channels for cathodic protection. Unlike conventional coatings, this method strategically modifies surface electrochemical potential profiles to disrupt corrosion initiation and spreading. By carefully adjusting process parameters, the technique induces surface and sub-surface optimized composition changes, leading to beneficial microstructure alterations that control the electrochemistry profile and inhibit both surface and 3D-corrosion damage. The effectiveness of this approach was further enhanced through remelting processes, which promoted Zn-Al mixing and created homogeneous compositions in the sacrificial anode melt-pools, thereby minimizing micro-galvanic potential risks. High-purity Zn patterns demonstrated significant suppression of intergranular corrosion, and subsequent electrochemical provide a framework the method's success in enhancing metal protection and reducing corrosion propagation. This innovative approach represents a substantial advancement in protecting AA5456 alloy from corrosion in demanding marine applications with the least intrusive and more persistent approach than a sacrificial anodic coating or laser surface melting and homogenization of previously sensitized Al-Mg.