Abstract
Duplex α + β’ brasses are widely used in drinking water distribution systems for tube fittings, valves, and ancillaries because they are low cost, easy to fabricate, and exhibit high mechanical strength. However, depending on application conditions and alloy composition, they may undergo dealloying and stress corrosion cracking. In this research, three different brass types, two leaded (CW617N and CW602N) alloys and one lead-free brass (CW724R), were investigated to assess their corrosion behavior and susceptibility to stress corrosion cracking (SCC) in simulated drinking water (SDW) solutions containing different chloride concentrations, compatible with drinking water composition requirements according to Moroccan standard NM 03.7.001. The corrosion behavior was assessed by electrochemical tests such as polarization curve recording and electrochemical impedance spectroscopy (EIS) monitoring, coupled to SEM-EDS surface observations. The susceptibility to SCC was investigated by slow strain rate tests (SSRT). The tests showed that corrosion was mainly under diffusion control and chlorides slightly accelerated corrosion rates. All alloys, and particularly CW617N, were affected by SCC under the testing conditions adopted and in general the SCC susceptibility increased at increasing chloride concentration.
Highlights
Duplex α + β’ brasses are widely used in drinking water distribution systems for tube fittings, parts of pumps, valves, faucets, and ancillaries because they are low cost, easy to fabricate, and exhibit high mechanical strength
Concerning dezincification of α and α + β’ brasses, two mechanisms were proposed, that is, selective Zn dissolution [1,2,3] and a more widely accepted selective dissolution model consisting in the initial dissolution of both Zn and Cu, followed by Cu redeposition [4,5,6,7,8]
The alloys suffered from spot dealloying that is preferential zinc and zinc and silicon dissolution already after 24 h immersion
Summary
Duplex α + β’ brasses are widely used in drinking water distribution systems for tube fittings, parts of pumps, valves, faucets, and ancillaries because they are low cost, easy to fabricate, and exhibit high mechanical strength. Depending on their composition, they may undergo different corrosion forms, such as dealloying and stress corrosion cracking and may determine human health concerns due to lead and, in the case of traditional dezincification resistant (DZR) alloys, arsenic release in drinking water. In this alloy a significant dealloying process cannot be avoided during long immersions (150 days) in simulated drinking water (SDW) [14]
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