Abstract
The inhibitive action of thiourea on the corrosive behaviour of ARMCO iron was investigated in deaerated 0.5 M H2SO4 solution, by means of electrochemical impedance spectroscopy. The inhibitor effectiveness increases with concentration, reaches a maximum (at about 1 mm) and then decreases. The adsorptive behaviour of thiourea on the electrode surface up to its peak follows a Frumkin-type isotherm with lateral repulsion, where the molecules are vertically adsorbed on the iron surface via the sulfur atom. Thiourea acts as a mixed inhibitor up to the critical concentration. It decreases the dissolution of iron and the hydrogen evolution reaction by blocking the electrode surface. The free energy of adsorption ΔG ad = −39 kJ mol−1 and the attraction constant a = −4.4.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
Abbreviations
- a :
-
attraction constant
- b :
-
Tafel slope (mV)
- C :
-
capacitance (F cm−2)
- c :
-
concentration (mol dm−3)
- E :
-
electrode potential (mV)
- E * :
-
activation energy (kJ mol−1)
- f :
-
frequency (Hz)
- ℛ:
-
gas constant
- T :
-
temperature (K)
- Z :
-
electrode impedance (Ω cm2)
- j :
-
current density (mA cm−2)
- K :
-
adsorption constant (dm3 mol−1)
- R :
-
resistance (Ω cm2)
- α:
-
transfer coefficient
- Θ:
-
inhibition efficiency (%)
- ω:
-
angular velocity (rad s−1)
- ν:
-
scan rate (mV s−1)
- a:
-
anodic
- c:
-
cathodic
- corr:
-
corrosion
- ct:
-
charge transfer
- p:
-
polarization
References
G. M. Brown, G. A. Hope, D. P. Schweinsberg and P. M. Fredericks, J. Electroanal. Chem. 380 (1995) 161.
G. Fabricius, Electrochim. Acta 39 (1994) 611.
G. I. Lacconi and V. A. Macagno, Electrochim. Acta 39 (1994) 2605.
J. Bukowska and K. Jackowska, J. Electroanal. Chem. 367 (1994) 41.
J. Sundrarajan and T. L. Rama Char, J. Appl. Chem. 11 (1961) 277.
B. Donnelly, T. C. Downie, R. Grzehowiak and D. Short, Corros. Sci. 14 (1974) 597.
P. Spinelli, G. Hoxha and G. Rocchini, Proceedings of the 7th European Symposium on Corrosion Inhibitors, Ann. Univ. Ferrara (1990) p. 949.
K. C. Pillai and R. Narayan, J. Electrochem. Soc. 125 (1978) 1393.
, Corr. Sci. 23 (1983) 151.
B. G. Ateya, B. E. Anadouli and F. M. Nizamy, 24 (1984) 497.
, 24 (1984) 509.
B. E. Anadouli, B. G. Ateya and F. M. Nizamy, 26 (1986) 419.
T. K. Ross and D. H. Jones, J. Appl. Chem. 12 (1962) 314.
G. Oakes and J. M. West, Br. Corros. J. 4 (1969) 66.
I. A. Ammar and F. M. El Khorafi, Werkst. & Korros. 24 (1973) 702.
R. Agrawal and T. K. G. Namboodhiri, Corros. Sci. 30 (1990) 37.
J. O'M. Bockris, M. A. Habib and J. L. Carbojal, J. Electrochem. Soc. 131 (1984) 3032.
S. Brinic, Z. Grubac, R. Babic and M. Metikos-Hukovic, Proceedings of the 8th European Symposium on Corrosion Inhibitors, Ann. Univ. Ferrara 1 (1995) 197.
S. M. Wilhelm and D. Abayarathna, Corrosion 50 (1994) 152.
I. Singh, 49 (1993) 473, and references cited therein.
J. R. Macdonald, J. Electroanal. Chem. 25 (1987) 223.
W. J. Lorentz and F. Mansfeld, Corr. Sci. 21 (1981) 647.
D. D. Perrin, ‘Dissociation Constants of Organic Bases in Aqueous Solutions’, Butterworths, London (1965) p. 449.
[24]E. J. Kelly, J. Electrochem. Soc. 112 (1965) 1255.
J. O'M. Bockris and Bo Yang, 4 (1991) 325.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Metikoš-Hukovič, M., Babić, R., Grubač, Z. et al. Impedance investigation of corrosion inhibition of armco iron by thiourea. J Appl Electrochem 26, 443–449 (1996). https://doi.org/10.1007/BF00251331
Received:
Revised:
Issue Date:
DOI: https://doi.org/10.1007/BF00251331