Some α + β’ brass components of drinking water distribution systems in Morocco underwent early failures and were investigated to assess the nature and extent of the corrosion attacks. They exhibited different corrosion forms, often accompanied by extensive β’ dezincification. In order to offer viable alternatives to these traditional low cost materials, the corrosion behavior of two representative α + β’ brass components was compared to that of brass alloys with nominal compositions CuZn36Pb2As and CuZn21Si3P, marketed as dezincification resistant. CuZn21Si3P is a recently developed eco-friendly brass produced without any arsenic or lead. Electrochemical tests in simulated drinking water showed that after 10 days of immersion CuZn21Si3P exhibited the highest polarization resistance (R_p) values but after longer immersion periods its R_p values became comparable or lower than those of the other alloys. After 150 days, scanning electron microscope coupled to energy dispersive spectroscopy (SEM-EDS) analyses evidenced that the highest dezincification resistance was afforded by CuZn36Pb2As (longitudinal section of extruded bar), exhibiting dealloying and subsequent oxidation of β’ only at a small depth. Limited surface dealloying was also found on CuZn21Si3P, which underwent selective silicon and zinc dissolution and negligible inner oxidation of both α and κ constituent phases, likely due to peculiar galvanic effects.

In the field of sustainable construction materials, the production of eco-friendly concretes, obtained by the addition of waste products such as biochar and recycled polymer particles, offers interesting alternatives to traditional materials. Biochar is a carbonaceous solid by-product obtained from the thermo-chemical conversion of biomass and its addition into concrete admixtures can offer an eco-friendly carbon sequestration solution, capable to slightly improve concrete properties. Recycled polymer materials can be used to partially replace conventional aggregates with the aim of obtaining lighter concretes that help to face the disposal challenge presented by this non-degradable plastic waste. However, the influence of these waste additions on the corrosion behavior of steel rebars embedded in these “eco-concretes” is still unexplored. Within this context, this work presents some results of an extensive study dealing with the concrete mechanical and physical properties and the rebar corrosion resistance during cyclic exposures to chloride-containing solutions.

The corrosion behavior of 20% silicon carbide particle reinforced (SiCp)/AZ80A (UNS M11800) and 20% SiCp/ZK60A (UNS M16600) metal matrix composites (MMC) was studied in 0.1 N and 1 N sodium sulfate (Na2SO4) or sodium chloride (NaCl) solutions at 25°C. The dissolution rate (Vcorr) of the two MMCs was obtained by weight-loss tests, while the evolution of their corrosion rate was followed by electrochemical measurements (linear polarization resistance measurements, anodic and cathodic polarization curve recording, and electrochemical impedance spectroscopy). Vcorr of UNS M11800 MMC was slightly higher than that of UNS M16600 MMC in sulfate solutions. By increasing the sulfate concentration from 0.1 N to 1 N, Vcorr of both MMCs increased around 10-fold, from ~20 mdd to ~200 mdd; in chloride solutions it was very high, around several thousand mdd. Polarization resistance (Rp) during 24 h immersion increased in sulfate solutions owing to the formation of partially protective corrosion products, while it remained constant or decreased in chloride solutions. The impedance spectra confirmed the difficulty to form uniform protective magnesium hydroxide (Mg[OH]2) layers on both MMCs.

This paper reports the effects of thermal aging between 650 and 850 °C on the localized corrosion behavior of lean duplex stainless steel (LDSS 2404). Critical pitting temperature (CPT) and double loop electrochemical potentiokinetic reactivation (DL-EPR) tests were performed. The localization of pitting attack and intergranular corrosion (IGC) attack after DL-EPR was investigated by optical (OM) and scanning electron microscopy (SEM) and by focused ion beam (FIB) coupled to SEM. Thermal aging caused the precipitation of mainly chromium nitrides at grain boundaries. Aging at 650 °C or short aging times (5 min) at 750 °C caused nitride precipitation mainly at α/α grain boundaries as a result of fast diffusion of chromium in this phase. Aging at 850 °C or aging times from 10 to 60 min at 750 °C also allowed the precipitation at the α/γ interface. Nitrides at γ/γ grain boundaries were observed rarely and only after long aging times (60 min) at 850 °C. Electrochemical tests showed that in as-received samples, pitting attack only affected the α phase. Conversely, in aged samples, pitting and IGC attack were detected close to nitrides in correspondence of α/α and α/γ grain boundaries depending on aging temperatures and times.

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.