Electrochemical origin for mitigated pitting initiation in AA7075 alloy with TiB2 nanoparticles

Abstract

High-strength Al alloys are susceptible to various corrosion degradation, and the notorious pitting process is the major source for catastrophic failures. Recent development of metal nanocomposites may overcome some of these degradation issues, but the mechanism is unclear due to the blurred pitting initiation and evolution. In this paper, we have systematically analyzed the microstructural change induced by TiB2 nanoparticle nano-treating in AA7075 alloy. The pitting initiation process is directly observed, and the high-resolution surface topographies are used to compare pits’ size and density. Pitted surfaces after long-term immersion are characterized by XPS to quantify the surface composition evolution. Considering these distinct microstructures and surface features, a potential-determined electrochemical model has been set up to explain this advantageous role of TiB2 nanoparticles in AA7075, and our results confirm that this understanding is ubiquitous even with other suitable ceramic nanoparticles.