The influence of sodium bromide in the corrosion and passivity of copper in borate buffer

M.R. GENNERO DE CHIALVO; M.F.L. DE MELE; R.C. SALVAREZZA; A.J. ARVIA

CORROSION SCIENCE

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 1988 vol. 28 p. 121 - 134

0010-938X

The electrodissolution, passivity and pitting corrosion of copper in borate buffer containing sodium bromide is studied by using potentiodynamic and potentiostatic techniques complemented with scanning electron microscopy. The voltammogram involves three regions. The first one corresponds to the electrodissolution of copper and the electroformation of a complex passive film containing Cu(I) and Cu(II) oxides and presumably some bromide ions. The second region involves the passivity of copper. In this region the transport of copper ions through the passive film is enhanced as the bromide ion concentration and temperature increase. The third region extends from a critical potential associated with the pitting corrosion of copper upwards. The critical potential decreases linearly with the sodium bromide concentration and in a complex way with temperature. Large hemispherical pits are observed in this potential region growing on the copper surface. The kinetics of pitting corrosion for high NaBr concentration can be described in terms of an instantaneous nucleation 3-D growth under diffusion control as previously reported for other metals and alloys in electrolytes containing other aggressive anions.