Hydrothermal vs. Electrochemical Synthesis of CaAl-Layered Double Hydroxides Smart Pigments for Steel Corrosion Protection

Intercalation efficiency and controlled release of organic molecules within CaAl-layered double hydroxides (LDHs) were investigated to develop smart pigments for corrosion protection of organic-coated steel. By systematically comparing hydrothermal and electrochemical syntheses, it is found that the electrochemical approach provides higher sebacate loading, whereas only autoclave post-treatment applied to either route leads to enhanced LDH crystallinity, smaller and more uniform particles, and greater inhibitor content (up to 40.9 wt %), and controlled release behavior. The improved structural features following autoclaving allow for a stronger link between release kinetics and overall corrosion protection performance. Hydrothermally prepared pigments display initially faster release and nobler corrosion potentials; however, post-treatment minimizes these differences and boosts the performance of electrochemical LDHs. The core novelty of this work lies in demonstrating that the interplay between tailored synthesis and post-synthesis treatment governs both the structure and function of LDH-based smart pigments. These findings provide practical guidance for the rational design of sustainable and effective inhibitors, highlighting the key relationships between LDH structure, inhibitor release, and protective efficacy on steel substrates.