Corrosion protection of zinc by LDH conversion coatings

Corrosion protection efficiencies of Layered Double Hydroxide (LDH) conversion coatings on zinc were studied. As-prepared LDH coatings contained nitrate anions that were exchanged for vanadate ones. Corrosion inhibitive properties of the LDH coatings were studied by electrochemical impedance spectroscopy (EIS) and scanning vibrating electrode technique (SVET) techniques in 0.05 M NaCl solutions. Electron microscopy, X-ray diffraction and release studies were employed to understand the mechanism of zinc protection. The LDH/vanadate system displayed about 20-fold increase in impedance and smaller local ionic currents compared to bare zinc. The protection was attributed to the partial release of vanadate anions from the LDH.