The Electrochemical Behavior of α,β^′-Brass in Basic NaNO₃Solutions

Abstract

The electrochemical behavior of an α,β -brass CuZn40Pb2 (CW617N) was studied in basic nitrate solutions with various basic pHs and nitrate ion concentrations. In all the chosen experimental conditions, corrosion at the open circuit potential proceeded by the galvanic coupling of the α and β phases, leading to a surface dezincification of the β phase. The study showed that the extent of the dezincification was affected by the presence of lead in the alloy but the pH was the major parameter. During polarization tests, a pseudo-passive or a passive stage followed by a breakdown was observed: corrosion phenomena mainly involved copper and zinc dissolution from the β phase. At pH 11, a Cu 2 O/PbO layer was efficient in achieving passivity of the brass. At pH 12, a Cu(OH) 2 -rich surface layer was formed: it was not protective enough, and complete dissolution of the β phase was observed leading to the removal of lead particles.

Dissolution Kinetics of α,β′-Brass in Basic NaNO3Solutions

“…Microstructure.-The metallurgical state of the brass was described in a previous study. 16 It corresponded to that of the center of a 65 mm diameter extruded rod ( Figure 2). The α phase (64 at.…”

“…Material.-The material used is the α,β -brass CuZn40Pb2 (CW617N) removed from extruded rods, as reported in a previous study. 16 Its chemical composition obtained from inductively coupled plasma (ICP) measurements is presented in Table I. Its microstructure was characterized by using optical microscope (OM) observations after abrading, polishing and etching the brass sample surface using Klemm II solution (24 g Na 2 S 2 O 3 , 5 g K 2 S 2 O 5 , 50 mL H 2 O) for 9 minutes.…”

Analytical Study of CuZn 30 and CuZn 39 Brass Surfaces in 3% NaCl Solution Under Polarization

“…Brasses continue to dissolve permanently by diffusion of zinc atoms from the CuZn alloy lattice without the electrochemical involvement of atomic Cu. Other studies suggest that dezincification can occur as a result of a dissolution of both zinc and copper in the brass [27], followed by a redeposition of Cu metal cation dissolved in solution on brass surfaces. Then a copper layer will be established thus accelerating zinc dissolution [10,28].…”

Importance of the surface and environmental conditions on the corrosion behavior of brass, steel and brass coated steel wires and brass coated steel cords

“…Brass corrosion usually initiates by the selective dissolution of zinc in solid solution into the copper matrix [12]- [14]. In acid and neutral solutions, simultaneous copper and zinc dissolutions are observed despite the establishment of a galvanic coupling that protects copper and depends on the copper/zinc ratio in the brass [13]- [16] [17]. As a result, the brass surface enriches in copper either by the highest dissolution rate of zinc compared to copper or by the redeposition of copper [18]- [20].…”

“…CuXO oxide presents both p-type and n-type semiconductor properties that depend on the solution pH and metal doping [25], [26]. Also, the cupric ions concentration near the brass surface seems the second major factor in Zn dissolution [16]. For brass-coated steels, the dissolution mechanism still starts with the dezincification of the brass due to the lower redox potential of the Zn/Zn 2+ couple compared to Cu/Cu 2+ or Fe/Fe 2+ [10].…”