Enhancing the corrosion resistance of the epoxy coating using CaAl LDH intercalated with L-cysteine and its derivatives as a pigment on steel substrate

Epoxy resin coating serves as a potential alternative for the corrosion protection of steels and is widely used in various applications. In this article, the CaAl layered double hydroxide intercalated with L-cysteine and its derivatives that act as corrosion inhibitors were developed. And then these CaAl layered double hydroxides were incorporated with epoxy resin as pigment to improve the corrosion resistance of coated Q235 steel. The optimum pH condition of preparing the layered double hydroxide precursor is 11.5, with an excellent crystallinity and an enhanced corrosion resistance with the impedance value of 2981 Ω cm2 and the current density of 1.02 × 10−5 A cm−2. On the other hand, the surface characterizations, such as X-ray Diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and high resolution transmission electron microscopy, confirm the successful intercalation of L-cysteine and its derivatives into the layered double hydroxide structure, in which the Epoxy/CaAl layered double hydroxide intercalated with the S-benzyl-L-cysteine exhibits more excellent corrosion resistance performance with the impedance value of 7.505 × 109 Ω cm2 due to its larger molecular volume which easily covering metal surfaces as well as an appropriate increase in the thickness of the layered double hydroxide.