Dissolution Kinetics of α,β′-Brass in Basic NaNO3 Solutions
Résumé
Corrosion tests at a constant anodic potential, referred to as dissolution tests, were performed to determine the dissolution kinetics of an α,β′-brass CuZn40Pb2 (CW617N) in a basic nitrate solution with and without mechanical loading. The corrosion behavior of the α,β′-brass was characterized by a two-step mechanism, with an initiation step for which the simultaneous dissolution of all the alloying elements of the β′ phase occurred only and a propagation step including at first, the afore-mentioned simultaneous dissolution process before a critical time tc and then, both simultaneous dissolution and dezincification of the β′ phase after tc. The pH and Cu concentration of the electrolyte near the brass surface were determined to be two of the major factors influencing the occurrence of the dezincification process. The dezincification of the β′ phase extended in depth by a percolation dissolution mechanism. Mechanical loading during the dissolution tests was observed to largely influence the dezincification process. It was assumed to open or close the pores present in the dezincified β′ phase, which promoted or slowed down the dezincification mechanism depending on the sign of the stress.
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