Self-assemble L-glycine and L-cysteine/polydopamine nanohybrid films coated on 304 stainless steel for corrosion study in sterile seawater

Corrosion of alloys is a serious problem in many industries because it can induce huge economic losses. Therefore, a suitable strategy needs to be applied to control the alloys' structural integrity. Stainless steels, which are widely used in the seawater environments, are susceptible to localized attack mechanisms, mainly to pitting corrosion. Therefore, the use of corrosion inhibitors and protective films is an essential approach to delay corrosion. Due to the enhanced awareness of ecological issues, green types of corrosion inhibitors are urgently needed for practical applications. In this study, muscle extracted protein, polydopamine (PDA) coating on 304 stainless steel (304ss), was successfully prepared using a self-assembly process. In order to enhance the adhesion of PDA on a substrate surface, a self-assembled of green inhibitors (L-gly and L-cys) was first implanted on a steel surface. The inhibitory properties of the coatings were verified by potentiodynamic polarization measurements and electrochemical impedance spectroscopy in sterile seawater. The electrochemical analysis demonstrated a positive shift in the corrosion potential and a decrease in the corrosion current density, especially for double-layer nanohybrid coatings. The FT-IR spectroscopy measurements of the coated surface confirmed the modification of 304ss surface by L-gly and L-cys and the PDA modified by L-gly and L-cys. The surface morphologies of the coatings were analyzed using SEM. The results showed that the formation of a low porosity and dense double-layer coatings could effectively retard corrosion.