Synergizing passive barrier and active ROS-mediated anti-MIC effect: A microenvironment-responsive LDH-ZIF@CaO₂/epoxy coating against microbiologically influenced corrosion

Microbiologically influenced corrosion (MIC) induced by sulfate-reducing bacteria (SRB) severely threatens the service of metal materials, and traditional purely passive barrier coatings fail to withstand the continuous attack of biofilms. Herein, a ternary composite material (LDH-ZIF@CaO₂) composed of CoAl-LDH, ZIF-67, and CaO 2 was synthesized and incorporated into epoxy resin to construct an anti-corrosion coating that integrates active antibacterial and anti-corrosion properties. The study reveals that this composite possesses typical microenvironment responsiveness: in the acidic environment generated by microorganism metabolism, the Co ions released from the system can catalyze H₂O₂ (produced by CaO₂ hydrolysis) to undergo a Fenton-like reaction, generating highly oxidizing hydroxyl radicals (•OH) and singlet oxygen ( 1 O₂). This achieves highly efficient eradication of SRB and biofilm detachment. Electrochemical impedance spectroscopy (EIS) tests indicate that when the CaO₂ loading is 200 mg, the coating exhibits the optimal anti-corrosion performance, maintaining high compactness and high impedance characteristics even after 30 d of immersion, the impedance value is 10 8  Ω cm 2 , which is 2 orders of magnitude higher than that of epoxy resin systems. Furthermore, this paper thoroughly elucidates that the excessive addition of CaO₂ (400 mg) leads to filler agglomeration, internal gas pressure, and oxidative degradation of the resin matrix caused by excessive free radicals, which conversely accelerates coating failure. This study provides a new theoretical basis and strategy for designing microenvironment-responsive, anti-MIC coatings.