Preparation of superhydrophobic Li-Al-Ala LDH/SA film with enhanced corrosion resistance and mechanical stability on AZ91D Mg alloy

摘要

Layered double hydroxide (LDH) films have attracted extensive attention in Mg alloy anti-corrosion due to their unique physical barrier function and ion exchange performance. However, most of the LDH films on Mg alloy have problems of harsh preparation conditions, poor anti-corrosion stability, and poor adhesion. In this paper, a typical Li-Al-alanine (Ala) LDH film has been successfully prepared on AZ91D Mg alloy surface under milder conditions using multi-arc ion plating and in-situ dipping for the first time. Then an improved vacuum impregnation further modified the Li-Al-Ala LDH film in an ethanol solution of stearic acid (SA) to improve its protective stability. The potentiodynamic polarization curves and electrochemical impedance spectra (EIS) showed that the Li-Al-Ala LDH /SA film's corrosion resistance is more than three orders of magnitude higher than that of the blank Mg alloy in 3.5 wt% NaCl, showing a highly increased corrosion resistance. The long-term immersion experiments found that the surface structure and corrosion resistance of the Li-Al-Ala LDH /SA film did not change much after immersion in 3.5 wt% NaCl for 432 h. The bonding force between the film and the Mg alloy substrate can reach grade 0 based on the standard from International Standardization Organization (ISO). And the hydrophobicity of the film can remain stable with the water contact angle (WCA) being steady at about 140 degrees after a certain distance of external abrasion, showing excellent mechanical wear resistance. The study provides a new milder approach to fabricating superhy-drophobic LDH films with durable anti-corrosion resistance, good adhesion, and mechanical stability on Mg alloy surface. @@@ [GRAPHICS] @@@ .

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