Synergistic effect of mixing cationic and nonionic surfactants on corrosion inhibition of mild steel in HCl: Experimental and theoretical investigations.

We studied the inhibition performances of IMB (imidazoline quaternary salt (IM) and benzotriazole (BTAH)) and IMO (IM and octyl phenol ethoxylates (OP)) mixtures as inhibitors of L245 steel placed in 10 vol% HCl solution at 298 K using experimental methods and theoretical calculations. We found that the mixtures adsorb on the steel by an endothermic spontaneous process, and the adsorption model follows Langmuir isotherm. The mixtures exhibit good synergistic inhibition effect, and the inhibition efficiency enhanced in turn (IMB < IMO). The relationship between synergistic effect of organic inhibitors and their energetic position of molecular frontier orbitals was discussed.