The Mg-Al layered double hydroxide(LDH)conversion coatings were first synthesized in situ to modify the AZ91D 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(icorr)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 icorr 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 after 15 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 com-bines core-shell LDH@ZIF-8 with LDH film on a Mg alloy surface to construct a hydrophobic film with excellent long-term anti-corrosion performance.

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

Ningxia Key Laboratory of Photovoltaic Materials,Ningxia University,Yinchuan 750021,China;School of Mechanical,Materials,Mechatronic and Biomedical Engineering,University of Wollongong,Wollongong,NSW 2522,Australia;China Special Equipment Inspection and Research Institute,Beijing 100029,China;State Key Laboratory of High-Efficiency Utilization of Coal and Green Chemical Engineering,Ningxia University,Yinchuan 750021,China

稀有金属（英文版）

[1]Pu-Bo Li;Yong-Xun Wang;Ze-Xi Shao;Bin-Tao Wu;Heng Li;Mang-Mang Gao;Kuan-Guan Liu;Ke-Ren Shi-.Enhanced corrosion protection of magnesium alloy via in situ Mg-Al LDH coating modified by core-shell structured Zn-Al LDH@ZIF-8)[J].稀有金属（英文版）,2022(08):2745-2758

SLLZ

Enhanced,corrosion,protection,magnesium,alloy,via,situ,Mg,LDH,modified,by,core,structured,ZIF,layered,double,hydroxide,conversion,coatings,were,first,synthesized,modify,AZ91D,through,urea,hydrolysis,adjust,values,possessed,best,compactness,good,crystallinity,compared,other,obtained,lowest,current,density,icorr,which,was,attributed,exchange,reaction,physical,barrier,against,owing,twisted,penetration,pathway,interlaced,sheets,Core,powder,stearic,acid,SA,further,wrapped,polyvinylidene,fluoride,PVDF,prepare,underlying,water,contact,angle,CA,reached,its,decreased,single,film,exhibited,high,durability,even,after,days,immersion,NaCl,solution,nano,shells,contributed,hydrophobicity,effectively,forming,beneficial,synergistically,promoting,between,intercalated,anions,chlorides,corrosive,media,This,work,provides,promising,approach,that,bines,surface,construct,excellent,long,term,anti,performance

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