AC impedance measurement of cystine adsorption at mild steel/sulfuric acid interface as corrosion inhibitor

Oezcan M.

JOURNAL OF SOLID STATE ELECTROCHEMISTRY, vol.12, no.12, pp.1653-1661, 2008 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 12 Issue: 12
  • Publication Date: 2008
  • Doi Number: 10.1007/s10008-008-0551-1
  • Journal Name: JOURNAL OF SOLID STATE ELECTROCHEMISTRY
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.1653-1661
  • Keywords: corrosion, inhibitor, adsorption, cystine, AC impedance, quantum chemical calculations, MOLAR HYDROCHLORIC-ACID, LOW-CARBON STEEL, SULFURIC-ACID, BENZIMIDAZOLE DERIVATIVES, H2SO4 SOLUTION, SCHIFF-BASES, HCL SOLUTION, IODIDE-ION, PURE IRON, MEDIA
  • Çukurova University Affiliated: Yes

Abstract

Alternating current (AC) impedance measurements of mild steel/sulfuric acid interface in the absence and in the presence of various concentrations of cystine (Cys-Cys) have been carried out in the 100 kHz-10 mHz frequency range. The results revealed that Cys-Cys is a good and effective inhibitor for mild steel corrosion in 0.5 M H2SO4 and its percent inhibition efficiency changes with its concentration. Changes in impedance parameters indicated the adsorption of Cys-Cys on the mild steel surface, which was verified by scanning electron microscope (SEM) and atomic force microscope (AFM) photographs. Adsorption of Cys-Cys on mild steel surface was found to obey the Langmuir adsorption isotherm with a standard free energy of adsorption (Delta G(ads)degrees) of -33.2 kJ/mol. Energy gaps for the interactions between mild steel surface and Cys-Cys molecule were found to be close to each other showing that Cys-Cys owns capacity to behave as both electron donor and electron acceptor.