User-Selectable Barrier, Sacrificial Anode, and Active Corrosion Inhibiting Properties of Al-Co-Ce Alloys for Coating Applications

An Al-Co-Ce alloy system has been developed with three important protection abilities when deployed as a metal coating over high-strength aerospace alloys such as AA2024-T351 (UNS A92024). These alloy coatings can serve as a local corrosion barrier with tunable anodic properties, act as a sacrificial anode (i.e., its open-circuit potential [OCP] is ca. 20 mV to 300 mV below that of AA2024-T351), and supply soluble ions that function as corrosion inhibitors. These three functions are not mutually exclusive. However, optimization of each may not be achieved in the same way. The Al-Co-Ce alloy system has demonstrated an excellent inherent resistance to corrosion due to its structural amorphicity and chemical composition, with electrochemical tunability based on solid solution Co and Ce composition. For example, the pitting potential (Epit) is more noble than the Epit of AA2024-T351 under acid, neutral, and alkaline conditions with pitting and repassivation potentials optimized by Co content. The gal...