Microstructural and residual stress effects on the electrochemical response of multi-layer friction surfaced AA5083

Friction surfacing (FS) is a solid-state coating process in which a consumable stud is plastically deformed and bonded to a substrate through frictional heating, producing a deposited layer with a highly refined microstructure. In the present study, the corrosion behavior of FS AA5083 was investigated by comparing the substrate, the deposited layer material, and the consumable stud material. Corrosion performance was evaluated using immersion tests, open circuit potential (OCP) monitoring, and cyclic polarization in chloride containing solutions with different pH values. The electrochemical response was correlated with grain size and residual stress state. The deposited layer exhibited a predominantly equiaxed and refined grains relative to both the substrate and the stud base material. Immersion tests revealed significant pit nucleation in all conditions, with the deposited layer showing the highest pit density. However, cyclic polarization results indicated that the deposited layer developed the highest pitting potential, suggesting an enhanced ability for repassivation after initial attack. These results demonstrate that, although grain refinement in FS layers may increase susceptibility to pit initiation, it can simultaneously promote improved resistance to pit propagation, highlighting the complex interplay between microstructure and localized corrosion behavior in frictionsurfaced aluminum alloys.