Active corrosion protection of micro-arc oxidation-based composite coating on magnesium alloy: Multiple roles of ionic liquid modified layered double hydroxide

• Published in: Ceramics international 2024-07, Vol.50 (14), p.26160-26170
• Main Authors: Liu, Yingxue, Duan, Jiaqian, Zhang, Jinglai, Guo, Xugeng
• Format: Article
• Language: English
• Subjects: Composite coatings; Corrosion protection; Ionic liquids; Micro-arc oxidation; Self-healing
• ISSN: 0272-8842; 1873-3956
• DOI: 10.1016/j.ceramint.2024.04.357

Multifunctional composite coatings have been extensively used to protect metal substrates from corrosion. However, the use of ionic liquids (ILs) to modify the micro-arc oxidation/layered double hydroxides (MAO/LDHs) composite coating, to our best knowledge, has not been reported for the corrosion protection on metal substrates. It is thus necessary to prepare the ILs-modified MAO/LDHs composite coatings and understand in depth their corrosion resistance and active anticorrosive mechanism. Herein, a composite coating is constructed by introducing the MgAl-LDH modified by a choline 3-morpholinopropanesulfonate [Ch][MOPS] ionic liquid on an MAO film (CM-LDH/MAO). It is found that the CM-LDH/MAO composite coating shows the optimal corrosion protection on magnesium alloy, with a corrosion current density of 8.38 × 10−10 A cm−2, clearly lower than those of the MAO and LDH/MAO coatings. More importantly, a small pitting appears at the edge of the CM-LDH/MAO film only after long-term exposure of 216 h in 3.5 wt% NaCl solution. Such an improvement of corrosion resistance can be ascribed to the synergetic mechanism including the physical barrier of the composite coating, the self-repairing ability of the LDH nanosheets on the microporous flaws of the MAO film, as well as the formation effect of the Mg-based chelates by the adsorption of the [Ch]+ cations and the re-adsorption of the [MOPS]– anions released from the LDH interlayers.