Corrosion Inhibition for Steel Surface Using a Polyacrylic Gel Sheet Containing Ni–Al Layered Double Hydroxide Prepared by Liquid-Phase Deposition

Ni–Al layered double hydroxide (LDH) was prepared on a steel plate and fumed alumina by the liquid phase deposition (LPD) method with NO2− inserted between the layers for rust prevention, and its corrosion-inhibition effect was investigated. Anion exchange of the synthesized LDH was carried out by immersing it in aqueous KOH and NaNO2 solutions, separately. The composition of the obtained Ni–Al LDH is typically [Ni(II)0.69Al(III)0.31(OH)2]OH0.31 in OH−-type LDH. Electrochemical measurements revealed the expansion of the passive area and a decrease in the corrosion current in the sample mixed with LDH, compared to the case with the pure polyacrylic gel sample. In particular, the corrosion current was reduced to less than half of the original in the samples mixed with NO2−–LDH. For the polyacrylic gel containing LDH, the anodic current was suppressed at all concentrations of the aqueous NaCl solution, and the corrosion current was approximately the same as the result of the polarization measurement. The corrosion-inhibiting effects due to Cl− absorption and NO2− release were confirmed. A good rust preventive effect was also observed in the hydrous LDH gel sheet intended to be exposed to the atmosphere where an arbitrary amount of Cl− ions is dissolved