Effect of α-tocopherol as a green inhibitor on chloride-induced corrosion of steel

Immersion of stainless-steel (SS) samples of type X4Cr13 in ethanol solutions of stearic acid, with and without addition of α-tocopherol, resulted in a modified surface with hydrophobic and corrosion resistance characteristics. We observed a double effect: a hydrophobic and corrosion-resistant surface of SS type X4Cr13 in a solution of 3.0% (wt.) NaCl at 25°C. The corrosion properties of bare and modified surfaces of stainless steel were tested by polarization and electrochemical impedance spectroscopy (EIS) in 3.0% (wt.) NaCl solution at 25°C. To observe the morphology and microstructures of sample surfaces, a Scanning Electron Microscope (SEM) was used after the electrochemical measurements. The results obtained from potentiodynamic polarisation measurements show that the inhibition effectiveness of X4Cr13 reached ~ 68% in cases when surfaces were modified in stearic acid alone (EIS measurements ~ 82%), while the values increased to more than 99.0% (for both methods) with addition of α-tocopherol (E307). Modification of the surface using an immersion method in an ethanol solution of stearic acid, especially with addition of α- tocopherol, appears to be a promising treatment for improving the corrosion resistance of stainless steel (SS) X4Cr13.