Acta Phys. -Chim. Sin. ›› 2012, Vol. 28 ›› Issue (02): 399-406.doi: 10.3866/PKU.WHXB201112142

• ELECTROCHEMISTRY AND NEW ENERGY • Previous Articles     Next Articles

Steric Effect of Alkyl Substituted Piperidin-4-one Oximes for Corrosion Control of Mild Steel in H2SO4 Medium

SENTHILKUMAR Annamalai1, THARINI Kumaravel2, SETHURAMAN Mathur Gopalakrishnan3   

  1. 1. Department of Chemistry, H.H The Rajah's College, Pudukkottai-622 001, Tamilnadu, India;
    2. Department of Chemistry, Raja Saraboji Government College, Thanjavur-613 005, Tamilnadu, India;
    3. Department of Chemistry, Gandhigram Rural Institute DU, Gandhigram-624 302, Tamilnadu, India
  • Received:2011-08-04 Revised:2011-12-06 Published:2012-01-11
  • Contact: SETHURAMAN Mathur-Gopalakrishnan E-mail:mgsethu@rediffmail.com

Abstract: Three synthesized piperidin-4-one oximes, 3-ethyl-2,6-diphenyl-piperidin-4-one oxime (A), 1- methyl-3-isopropyl-2,6-diphenyl-piperidin-4-one oxime (B), and 3-isopropyl-2,6-diphenyl-piperidin-4-one oxime (C), were tested at different concentrations to determine their ability to inhibit corrosion of mild steel in 1 mol·L-1 H2SO4 and measured by a mass loss method (at various temperatures), polarization and impedance measurements, X-ray diffraction (XRD), scanning electron microscopy (SEM) with energydispersive X-ray spectroscopy (EDS), and a quantum chemical method. The synergistic influence of compounds A, B and C with iodides has also been evaluated. All three compounds show good inhibition efficiency in the following order: A>B>C. Compounds A, B and C were found to physically adsorb on the surface of mild steel while obeying the Temkin isotherm. Polarization measurements indicated that these compounds behave as a mixed mode inhibitor. XRD and SEM with EDS studies revealed the formation of a protective barrier on the mild steel surface by these oximes. The electron donating ability of the studied molecules was tested using semi empirical methods. The studies revealed that the oxime nitrogen, the piperidine moiety, and the phenyl ring assist largely in corrosion control. The studies also showed that the steric crowding by the alkyl group in the piperidine ring affects the inhibitor efficiency. Further, it is interesting to note that all of the studied compounds exhibit synergism with iodide ions.

Key words: Oxime, Steric crowding, Polarisation, Impedance, X-ray diffraction, Scanning electron microscopy