Enhanced anticorrosion of methyl acrylate by covalent bonded N-alkylpyridinium bromide for X70 steel in 5 M HCl

•Methyl acrylate connects covalently with alkylpyridinium bromide to produce MPA-n.•MPA-n adsorbs on X70 steel surface via O atom of MA moiety and positive pyridinium ring.•The interaction energy of MPA-n with iron increases with prolonging the alkyl chain.

Methyl acrylate connects covalently with alkylpyridinium bromide to build N-alkyl-3-(2-methoxycarbonyl-vinyl)pyridinium bromide (MPA-n, n = 8–14). MPA-n inhibited X70 steel from corrosion in 5 M HCl with inhibition efficiency of 98% and the inhibition capacity was in the order of MPA-14 > MPA-12 > MPA-10 > MPA-8. Quantum chemical calculation unveiled that MPA-n adsorbed on iron surface by O atom in MA moiety offering electrons to d orbital of iron and by π* orbital of pyridinium accepting electrons from iron, and MPA-n with longer alkylchain possessed higher EHOMO, lower ΔE, larger molecular volume and dipole moment, all suggesting the same corrosion inhibition order as that in experiments.

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