Enhancing anticorrosive performance of epoxy primers using MBT-modified LDH and zinc phosphate synergy

Abstract

An epoxy-based anticorrosive primer was developed by combining zinc phosphate, a widely used anticorrosive pigment, with the organic corrosion inhibitor 2-mercaptobenzothiazole (MBT) intercalated into Zn/Al/Mg layered double hydroxides (LDH). LDH was synthesized using a co-precipitation technique involving zinc, aluminum, and magnesium. To improve its corrosion resistance, MBT was incorporated into LDH, and Fourier-transform infrared spectroscopy (FTIR) was used to confirm the structural changes and chemical interactions. Primer formulations with different ZnP concentrations (2.5, 4, and 5.5%) and 1% LDH or MBT–LDH were created to test their combined corrosion protection. Mechanical testing showed that LDH/MBT–LDH increased the hardness (up to 5H) and scratch resistance while maintaining good impact resistance and flexibility across all formulations. Chemical resistance was maintained by coatings passing acid, alkali, and solvent tests. Salt spray exposure for 500 h showed that MBT–LDH coatings with 5% ZnP had excellent corrosion resistance and low rust growth. The synergy of ZnP and MBT provided active corrosion prevention, while the LDH structure improved the barrier properties and minimized localized corrosion. These data show that LDH and MBT–LDH are effective alternatives to chromate-based inhibitors in epoxy coatings.

Graphical Abstract

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