Efficiency of cationic gemini surfactants with 3-azamethylpentamethylene spacer as corrosion inhibitors for stainless steel in hydrochloric acid

The corrosion inhibition efficacy of two cationic gemini surfactants with 3-azamethylpentamethylene spacer on AISI 304 stainless steel in 3 M HCl was investigated by polarisation measurements and electrochemical impedance spectroscopy (EIS). Following corrosion testing, the surface of stainless steel samples was studied by scanning electron microscopy (SEM). The results showed that the effectiveness of corrosion inhibition were up to 95% depending on the C-chain length and the gemini surfactant concentration. The inhibitive action is due to an adsorption of inhibitor molecules onto the metal surface following a Langmuir adsorption isotherm model. The variation in the cathodic and anodic branches reveals that the surfactants tested act as mixed-type inhibitors. The highest inhibition efficiency was reached around the values of the critical micelle concentration. The results obtained from both polarisation and EIS measurements are in a good agreement.