Functionalized Double Layered Hydroxide Coating on Aluminum Alloy for Enhanced Alkaline Resistant Anti-Corrosion

摘要

Growth of oriented Zn-Al LDH film on AA6061 substrate was achieved through hydrothermal crystallization by which partial dissolved alloy substrate during the hydrothermal synthesis was used as the in-situ Al source with addition of external Zn precursor as Zn source. With increasing hydrothermal temperature and time, the LDH film grown on AA6061 became increasing oriented and intergrowth, resulting in increasing dense film structure. Depending on LDH crystallinity, film density and hydrophobicity, LDH film could significantly enhance the corrosion resistance of AA6061 in 0.1 M NaOH solution (pH of 13) by reduction of corrosion current (i_(corr)) by four orders of magnitude. When Poly(methyl methacrylate) (PMMA) or sodium dodecyl sulfate was intercalated into the LDH film, the functionalized LDH film exhibited even more reduced i_(corr) and also more positive corrosion potential (E_(corr)), as an indication of reduction of the corrosion activity of AA6061. The improved corrosion resistance of intercalated LDH film could be attributed to the dense film structure of polymer - LDH composite. In contrast, when PMMA and some other polymers were coated on the LDH film, polymer acted as a physical protection layer enabling only for reduction in corrosion rate without metal passivation.