Douglas K. da Silva,^a,b) Gisele C.B. Ribas, ^b) Maico T. da Cunha,^a,b) Silvia M.L. Agostinho,^b) Paulo R.P. Rodrigues^a)*

^a) GPEL – Electrochemical Research Group of DEQ / UNICENTRO – Department of Chemistry / State University of the Center-West, Guarapuava - Paraná, Brazil

^b) IQUSP – Institute of Chemistry of the University of São Paulo, São Paulo, SP, Brazil

Abstract

In this work the characteristics of corrosion and inhibition of 1008 stainless steel in 0.5 mol.L^-1 H₂SO₄ were investigated by physical and electrochemical methods. Organic compounds containing the heteroatom of N as benzotriazole (BTAH), tolytriazole (TTAH) and mixtures of BTAH + TTAH were used as corrosion inhibitors. The techniques used were: open circuit potential, anodic potentiodynamic polarization measurements, chronoamperometry, electrochemical impedance spectroscopy, weight loss and optical microscopy. The anodic polarization showed that the increase of both concentrations BTAH or TTAH diminishes the current density in all the potential anodic range studied; these results together with the weight loss measurements suggest that the inhibitors act by blocking the surface and that the interaction among them is only of destructive nature when inhibiting efficiency is approximated 100%, revealing that at low concentration both inhibitors act without affecting the mechanisms of the cathodic processes, but the anodic polarization curves in presence of the TTAH showed a strong inhibitive effect in all the potential range studied. However, both gravimetric and electrochemical results suggest a synergic effect for the inhibitive efficiency of the mixture 1.10^-3 mol.L^-1 BTAH + 1.10^-3 mol.L^-1 TTAH.

Keywords: carbon steel 1008, corrosion, inhibitor, sulfuric acid, benzotriazole, tolytriazole.

Texto disponível em PDF

Referências

1. G. Trabanelli, Corrosion Mechanisms, (F. Mansfeld) New York, Marcel Dekker (1987).        [ Links ]

2. P. Spinelli and G. Hoxha, "Evaluation of Armco iron corrosion rate by impedance techniques", 9­^th European Congress on Corrosion, Utrecht, The Netherlands, 2/6 oct., p. FU-15 (1989).

3. S. Brinic, Z. Grubac, R. Babic and Metikos-Hukovic, "Study of the thiourea adsorption on iron in acid solution", Proceedings of the 8^th European Symposium on Corrosion Inhibitors (7SEIC), Ann. Univ. Ferrara, v. 1, p. 197 (1995).

4. P.R.P. Rodrigues, "O benzotriazol como inibidor de corrosão para o ferro e ligas ferrosas em meio de ácido sulfúrico", Tese de Doutorado, IQUSP – São Paulo, SP (1997).

5. M.T. Cunha, "Estudo comparativo dos inibidores benzotriazol e tolitriazol na oxidação de materiais ferrosos em meio de ácido sulfúrico”, Dissertação de Mestrado, IQUSP – São Paulo, SP (2003).

6. I.V.S. Santos, "Filme de Benzotriazol sobre Materiais Ferrosos: Formação, Resistência, Efeito de Aditivos e do Transporte de Massa", Dissertação de Mestrado, IQUSP – São Paulo, SP (2003).

7. K. Nobe, N. Elkadar, Corrosion 37 (1981) 4.

9.  K. Nobe, N. Elkadar, Corrosion 32 (1976).

10. G.K. Gomma, Materials Chemistry and Physica 56 (1998).

11. M.T. Cunha, P.R.P. Rodrigues, S.M.L. Agostinho, “Construção de um potenciostato com interface de baixo custo para medidas eletroquímicas”, Anais do XVIII Simpósio Brasileiro de Eletroquímica e Eletroanalítica, Araraquara, São Paulo (2000).

*Corresponding author. E-mail address: prprodrigues@unicentro.br