Synergistic corrosion inhibition of MnOx and L-cystine loaded α-ZrP sheets for enhancing the active/passive protection of waterborne epoxy coating

An environmentally friendly anti-corrosion coating was developed by incorporating MnO x and L-cystine loaded α-ZrP. During the preparation of ZPML (α-ZrP/polydopamine/MnO x /L-cystine) composite particles, a redox reaction occurred between MnO 2 and L-cysteine. MnO 2 was reduced to produce MnO x , which contained abundant oxygen vacancies that effectively passivated the steel substrate. Simultaneously, L-cysteine was oxidized to form L-cystine, which had more active inhibitory sites. Moreover, the decoration of MnO x nanoparticles on ZPML suppressed sheet aggregation and restacking, while incorporating L-cystine improved the interface compatibility between ZPML and the waterborne resin matrix, both of which significantly reduced coating defects and enhanced the physical barrier function of ZPML composite particles. This synergistic active inhibition effect of MnO x and L-cystine, combined with the enhanced barrier properties of α-ZrP sheets, resulted in the ZPML/WEP coating demonstrating exceptional long-term anti-corrosion performance. Impressively, the |Z| 0.01 Hz value remained above 10 10 Ohm cm 2 even after 210 d of immersion in a 3.5 wt% NaCl solution. This research presents a new strategy for enhancing the long-term anti-corrosion performance of waterborne epoxy coatings.