Enhanced corrosion inhibition behavior of carbon steel in aqueous solution by Phosphoserine-Zn2+ system

The corrosion inhibition effect of carbon steel in aqueous solution was using a synergistic mixture of an environmentally friendly inhibitor system phosphoserine (PS) and Zn²⁺ using gravimetric studies, potentiodynamic polarization, and electrochemical impedance studies. Potentiodynamic polarization studies showed that the inhibitor system is a mixed type inhibitor. Electrochemical impedance studies of the metal/solution interface indicated that the surface film is highly protective against the corrosion of carbon steel in the aqueous solution. X-ray photoelectron spectroscopic analysis of the protective film exhibited the presence of the elements viz., iron, phosphorus, nitrogen, oxygen, carbon, and zinc. The chemical shifts in the binding energies of these elements inferred that the surface film is composed of oxides/hydroxides of iron, Zn(OH)₂, and Fe(II)/(III)-Zn(II)-PS] complex. Further, the surface examination techniques viz., FTIR, SEM, and AFM studies confirm the formation of an adsorbed protective film on the carbon steel surface. Based on the results obtained, a suitable mechanism of corrosion inhibition is presented.