Assessment of EFM as a new nondestructive technique for monitoring the corrosion inhibition of low chromium alloy steel in 0.5 M HCl by tyrosine

Electrochemical frequency modulation (EFM), a nondestructive corrosion measurement technique that can directly give values of corrosion current without prior knowledge of Tafel constants, is applied here to investigate the inhibition performance of tyrosine (Tyr) toward corrosion of low chromium alloy steel in 0.50 M HCl. Measurements were conducted under various experimental conditions in the range of temperature (20-60 A degrees C). Results obtained from EFM were compared with other traditional corrosion monitoring techniques, namely Tafel extrapolation, impedance, and weight loss. Polarization measurements showed that Tyr acted as a mixed-type inhibitor with cathodic predominance. The inhibition process was attributed to the formation of an adsorbed film on the metal surface that protected the metal against corrosive agents. Energy dispersive X-ray spectroscopy and scanning electron microscopy examinations of the electrode surface confirmed the existence of such an adsorbed film. The inhibition efficiency increased with increase in Tyr concentration, while it decreased with solution temperature. The adsorptive behavior of Tyr on the electrode surface followed Temkin-type isotherm. Thermodynamic functions for the adsorption process were determined. The data obtained from the different methods were in good agreements, which indicated that the EFM technique was valid for monitoring the corrosion inhibition under the studied conditions.