Influence of Parameters in LDH Preparation on Its Morphology Structure and Corrosion Protection Property

Layered double hydroxide (LDH) has been widely used in the field of corrosion protection. LDH nanofillers can act as multifunctional additives in coatings based on the physical barrier effect and anion exchange effect. However, the preparation of the typical co-precipitation method needs to be simplified to realize large-scale industrialization. In this work, a wide range of synthesis parameters, including solution-mixing mode, reaction atmosphere, reaction pH control, titration rate and post-treatment on the obtained LDH, were systematically studied, and it was found that the one-step solution-mixing synthesis procedure and the adoption of N2 atmosphere were able to alleviate the carbonate contamination to some degree. However, the one-step solution-mixing synthesis procedure has a negative influence on the formation of LDH, probably due to insufficient reaction, while the hydrothermal post-treatment is able to promote the continual growth of the LDH platelet and, thus, lead to an increase in crystallinity and particle size. Green inhibitor aspartates were used to modify LDH, and the electrochemical test results indicated that the adoption of N2 atmosphere was able to clearly increase the corrosion protection ability of LDH, with an Rp value of 3.86 kΩ·cm2 after immersion for 96 h in 0.1 mol/L NaCl, probably due to the intercalation of a relatively large amount of inhibitor anions since less carbonates were intercalated, followed by the LDH synthesized via co-precipitation without N2 protection, pH control and hydrothermal post-treatment with an Rp value of 3.00 kΩ·cm2. The LDH sample without inhibitor intercalation presented a corresponding Rp value of 2.45 kΩ·cm2. Notably, the one-step solution-mixing method and a fast titration rate in co-precipitation would have a negative influence on the corrosion protection of LDH, probably due to insufficient reaction. This work could shed light on the simplification of LDH preparation, and it is able to provide a solid foundation and technical support for the wide promotion and application of LDH in anti-corrosion and other fields in the near future.