Corrosion Inhibition of AA2024-T3 By Smart Polyelectrolyte Coacervates Responsive to Both Acidic and Alkaline Environments

Abstract

Previously reported pH-responsive corrosion-protective coatings based on the layer-by-layer assembled polyelectrolytes responded to either a pH increase or decrease caused by cathodic or anodic reactions in corrosion, respectively, but not to both. The layer-by-layer technique, which is the standard method to prepare these coatings, requires dozens of layers to make the coatings useful for corrosion protection by safely enclosing corrosion inhibitors. In this study, polyacrylic acid was directly added into polyethylenimine to make polyelectrolyte coacervates via electrostatic interactions. The coating consisting of polyelectrolyte coacervates was capable of entrapping the SrCrO4 inhibitor and releasing the inhibitor at both acidic and alkaline pH. The concentration of released SrCrO4 exceeded the threshold for the corrosion protection of AA2024-T3 and the corrosion resistance of AA2024-T3 was improved, as evidenced by electrochemical methods including cyclic potentiodynamic polarization and electrochemical impedance spectroscopy. The developed polyelectrolyte coacervates open a pathway for creating a dual-pH release system in a facile and fast way, which can be applied as main components in active corrosion-protective coatings for Al alloys.