Spectroscopic Methods Used for Analyzing Protective Film Formed by L-Histidine on Carbon Steel

The corrosion inhibition of carbon steel (CS) using the “green” inhibitor, L-Histidine (L-His) was investigated. This studywas conducted at pH 7.8. The effect caused by Zn2+ additive also was investigated. The study was done over a range of concentrations. Gravimetric method and electrochemical methods were applied. It was found that the L-Histidine acts as a good inhibitor at pH 7.8. The inhibition efficiency increases with increasing L-His concentration. The addition of Zn2+ to L-Histidine significantly increased the inhibition efficiency. Tafel results indicated that decrease the corrosion current (Icorr) value. The influence of biocide SDS on the inhibition efficiency of L-Histidine – Zn2+ system has been investigated. Also it is evident that at minimum concentration of biocides added to the inhibitor system, 100 % biocidal efficiency is noticed. The protective film formed on the metal surface has been analyzed by FT-IR, SEM and EDAX spectra. It is found that the protective film consists of Fe2+ - L-Histidine complex and Zn(OH)2