Growth Mechanism and Corrosion Resistance of a Co-Al Layered Double Hydroxide Film Grown In Situ on a Steel Substrate

The growth mechanism of layered double hydroxide (LDH) films grown in situ on steel via hydrothermal treatment is still unclear. In this study, the mechanism of Co-Al-CO3-LDH film grown in situ on a steel substrate was investigated in detail. During the hydrothermal reaction, the in situ growth process of Co-Al LDH on steel involved three steps: (1) hydrolysis of Al3+ and etching of the steel surface, (2) hydrolysis of urea and promotion of LDH nuclei, and (3) crystallization of LDH. More importantly, the generation of Al⁡(OH)3 determined the integrity of the LDH film grown on the steel surface, and a suitable heating rate was also the key factor that affected the growth of the ordered and regular LDH nanoflakes. Therefore, this work provides a comprehensive understanding of the in situ LDH growth mechanism on steel and may facilitate optimal LDH film preparation.