Abstract
Corrosion inhibition of mild steel in 0.5 mol/L H2SO4 was investigated in the absence and presence of different concentrations of thiosemicarbazide. The inhibition efficiency of thiosemicarbazide was studied by electrochemical impedance methods, potentiodynamic polarization and scanning electron microscopy at different inhibitor concentrations. Inhibition efficiency, corrosion rate and surface coverage were evaluated at different concentrations of thiosemicarbazide. Electrochemical impedance plots indicated that the presence of the inhibitors increased the charge transfer resistance of the corrosion process, increasing the inhibition efficiency. Polarization curves showed that this compound acted as mixed type inhibitor. The results of the investigation showed that this compound had good inhibiting properties for mild steel corrosion in 0.5 M sulfuric acid. The adsorption isotherm studies showed that Thiosemicarbazide adsorbed chemisorbed and formed a stable surface complex on the mild steel surface. And Langmuir obeyed the adsorption isotherm. Scanning electron microscopy analysis shows that, the surface morphology of the polished mild steel in the presence of thiosemicarbazide as inhibitor is smoother surface as compared with polished mild steel specimen in the absence of inhibitor.
Highlights
The corrosion of materials is one of the main problems facing industrial processes, generating huge financial losses
The Nyquist diagrams show a single semicircle shifted along the real impedance axis (Zreal), indicating that the corrosion of mild steel in 0.5 M H2SO4 solution is controlled by a charge-transfer process [21]
The impedance response of mild steel in inhibited solution has significantly changed after the addition of thiosemicarbazide in the corrosive media, and the impedance of inhibited substrate increased with increasing thiosemicarbazide concentration
Summary
The corrosion of materials is one of the main problems facing industrial processes, generating huge financial losses. The use of organic inhibitors for preventing corrosion is a promising solution [2] These organic inhibitors are usually adsorbed on the metal surface by the formation of a coordinate covalent bond (chemical adsorption) or the electrostatic interaction between the inhibitor and the metal (physical adsorption) [3]. These compounds were adsorbed, or formed a protective layer/insoluble complex on the metal surface and block the active corrosion sites [4]. Potentiodynamic polarization, electrochemical impedance techniques and scanning electron microscopy analysis were studied
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