Adsorption and inhibitive properties of a Schiff base for the corrosion control of carbon steel in saline water

Abstract

A Schiff base, namely N-(2-hydroxybenzylidene) thiosemicarbazide (HBTC), was investigated as inhibitor for carbon steel in saline water (SW) using electrochemical measurements such as: potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The morphology of the surfaces before and after corrosion was examined by Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM/EDS). The results showed that HBTC acts as corrosion inhibitor in SW by suppressing simultaneously the cathodic and anodic processes via adsorption on the surface which followed the Langmuir adsorption isotherm; the polarization resistance (R_p) and inhibition efficiency (IE) increased with each HBTC concentration increase. SEM/EDS analysis showed at this stage that the main product of corrosion is a non-stoichiometric amorphous Fe³⁺ oxyhydroxide, consisting of a mixture of Fe³⁺ oxyhydroxides, α-FeOOH and/or γ-FeOOH, α-FeOOH/γ-FeOOH and Fe(OH)₃.

Keywords:

• Carbon steel
• corrosion inhibition
• electrochemical measurements
• SEM/EDS

Acknowledgments

This work was supported by CNCSIS – UEFISCSU, project number PNII – IDEI 422 code /2008. The author thanks to the IDEI/Grant-Program, 422/2008 competition and Acad. Prof. Dr. Aurelian Gulea from Moldova State University, Chisinau for Schiff base preparation and for mentioned SEM / EDS analysis accomplishment.