Insight into inhibition behavior of novel ionic liquids for magnesium alloy in NaCl solution: Experimental and theoretical investigation

[Display omitted] •Inhibition behavior of three novel ionic liquids for Mg alloy is studied.•The highest inhibition efficiency is 91.9% for [OTP][NTf2] in 0.05 wt.% NaCl.•The inhibition efficiency is improved with the substituted elogation of alkyl chain.•The possible inhibition mechanism is proposed by theoretical and XPS result. Three ionic liquids, decyl triphenyl phosphonium bis(trifluoromethylsulfonyl)amide ([DTP][NTf2]), tetradecyl triphenyl phosphonium bis(trifluoromethylsulfonyl)amide ([TTP][NTf2]), and octadecyl triphenyl phosphonium bis(trifluoromethylsulfonyl)amide ([OTP][NTf2]), are firstly synthesized and their corrosion inhibition for AZ31B magnesium alloys in 0.05 wt.% NaCl solution is measured by electrochemical tests. The surface morphology is determined by scanning electron microscopy (SEM) and atomic force microscopy (AFM), which testifies the formation of protective films on Mg alloy surface. The inhibition mechanism is further elucidated by X-ray photoelectron spectroscopy (XPS), first principle calculation along with molecular dynamics (MD). Possible inhibited mechanism is proposed finally. The highest inhibition efficiency is 91.9% by addition of 0.30 mM [OTP][NTf2] in corrosive media.