Enhanced corrosion protection of magnesium alloy via in situ Mg-Al LDH coating modified by core-shell structured Zn-Al LDH@ZIF-8  

作　　者：Pu-Bo Li Yong-Xun Wang Ze-Xi Shao Bin-Tao Wu Heng Li Mang-Mang Gao Kuan-Guan Liu Ke-Ren Shi 

机构地区：[1]Ningxia Key Laboratory of Photovoltaic Materials,Ningxia University,Yinchuan,750021,China [2]School of Mechanical,Materials,Mechatronic and Biomedical Engineering,University of Wollongong,Wollongong,NSW,2522,Australia [3]China Special Equipment Inspection and Research Institute,Beijing,100029,China [4]State Key Laboratory of High-Efficiency Utilization of Coal and Green Chemical Engineering,Ningxia University,Yinchuan,750021,China

出　　处：《Rare Metals》2022年第8期2745-2758,共14页稀有金属（英文版）

基　　金：financially supported by the Project of Key Research Plan of Ningxia (Nos.2020BDE03012 and 2018BEE03008);the Science and Technology Project for Young Talents of Ningxia (No.TJGC2019042)

摘　　要：The Mg-Al layered double hydroxide(LDH)conversion coatings were first synthesized in situ to modify the AZ91 D alloy through urea hydrolysis to adjust the pH values(9.4,10.4,11.2 and 11.4).The pH 11.2 Mg-Al LDH possessed the best compactness and good crystallinity compared to other in situ LDH coatings and obtained the lowest corrosion current density(i_(corr))of(2.884×10^(-6)±0.345×10^(-6))A·cm^(-2),which was attributed to the anion-exchange reaction of LDH and the physical barrier against corrosion owing to the twisted penetration pathway of the interlaced LDH sheets.Core-shell structured Zn-Al LDH@ZIF-8 powder modified with stearic acid(SA)was further wrapped with polyvinylidene fluoride(PVDF)to prepare a hydrophobic double-layered coating on the underlying pH 11.2 Mg-Al LDH(SLLZ).The water contact angle(CA)of the SLLZ coating reached 105.6°,and its i_(corr)decreased to(3.524×10^(-7)±0.214×10^(-7))A·cm^(-2)compared with a single pH 11.2 film.The SLLZ coating exhibited high durability and corrosion protection,even after15 days of immersion in NaCl solution.The PVDF,SA and ZIF-8 nano-shells contributed to good hydrophobicity,effectively forming a physical barrier.The Zn-Al LDH core and underlying in situ Mg-Al LDH were beneficial for synergistically promoting anion-exchange reaction between the intercalated anions of LDH and chlorides in corrosive media.This work provides a promising approach that combines core-shell LDH@ZIF-8 with LDH film on a Mg alloy surface to construct a hydrophobic film with excellent longterm anti-corrosion performance.

关 键 词：Mg alloy Layered double hydroxide Corrosion protection COATING Metal-organic frameworks 

分 类 号：TG174.4[金属学及工艺—金属表面处理]