In this study, electrochemical measurements were carriet out to characterize the behaviour of Admiralty Brass in a 0.5 M sodium chloride solution in the absence of inhibitors and in the presence of a mixture of alkylamines and thiazol-derived products. This formulation is employed for water treatment in cooling circuits.
The steady-state current voltage curves and the impedance diagrams were obtained with a rotating disc electrode in order to control the hydrodynamic conditions.
The first part of this study deals with the results obtained for two concentrations of the mixture and for two immersion times at the corrosion potential. It has been shown that the inhibitive effect is more marked when the concentration increases from 10 to 50 mg/l. A slight decrease of the protection of the brass surface is observed when the immersion time increases
The second part of this study is a comparison of the inhibitive effects of each compound of the mixture, on one hand, for concentration values used in the water treatment (0.1 mg/l of tbe solution containing the thiazol-derived products and 1 mg/l of the solution containing the alkylamines) and on the other hand, for identical concentration values (5 mg/l ). For 0.1 mg/l, no inhibitive action of thiazol-derived products could be detected. Thus, the corrosion protection of cooling circuits in Admiralty brass is attributed essentially to the alkylamines. They form a thick, protective film at the electrode surface.
For higher concentration values, the addition of 0.5 mg/l of thiazol-derived products to 5 mg/l of alkylamines improves the corrosion resistance of brass.
Corrosion, inhibition, brass, electrochemical methods, alkylamines, thiazol-derived products, water treatment, cooling circuits.
N. Pebere, URA CNRS 445, Laboratoire des Matériaux, Équipe
Métallurgie Physique, ENSCT, 118 route de Narbonne, 31077 Toulouse Cedex,