Guozhe Meng

Electrochemically assisted silanization treatment of an aluminum alloy under oxygen pressure for corrosion protection

A silane film was prepared on an aluminum alloy through electrochemically assisted deposition under different oxygen pressure levels. Surface morphology observation and corrosion resistance evaluation of the silanized aluminum alloy showed that silane film deposition was enhanced by exerting oxygen pressure during the electrochemically assisted silanization (EAS). The coverage degree and corrosion resistance of the silane film prepared under oxygen pressure increased compared with those of the silane film prepared by dipping or electrochemically assisted deposition without oxygen pressure. These phenomena were explained by the increased OH− ion generation rate under oxygen pressure due to the facilitated oxygen diffusion and by the fact that the OH− ions not only can accelerate the condensation reaction of the silanols but also increase the amount of hydroxyl groups on the surface of the Al alloy, consequently improving the formation of the silane film.

Anticorrosion Performance of LDH Coating Prepared by CO2 Pressurization Method

Many surface treatment methods are used to improve the corrosion resistance of magnesium alloys. LDH (layered double hydroxides) conversion coatings are currently found in the most environmentally friendly and pollution-free coatings of magnesium alloy. In this study, the CO2 pressurization method was applied to the preparation of LDH coating on magnesium alloy for the first time. The effect of CO2 pressurization on the formation and corrosion resistance of LDH coating on AZ91D alloy was investigated. The hardness and adhesion were significantly higher on LDH coating in the case of CO2 pressurization than it is in atmospheric pressure. The surface and cross-sectional morphologies show that LDH coating is more compact in the case of CO2 pressurization than with atmospheric pressure. The results of the polarization curve, hydrogen evolution, and immersion tests indicate that the corrosion resistance of the LDH coating prepared by the CO2 pressurization method was significantly improved.