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Additional tertiary treatment of secondary-treated municipal wastewater (MWW) is necessary to reduce its scaling potential for use in power plant cooling systems. In this study corrosiveness of three tertiary-treated municipal wastewaters (acidified MWW, MWW treated by nitrification–filtration, and MWW treated by nitrification–filtration and granular activated carbon adsorption) towards mild steel, copper, and cupronickel alloys was assessed. pH, ammonia, and organic matter were identified as important corrosion influencing parameter in tertiary-treated municipal wastewater. Corrosiveness of wastewater towards metal alloys increased after tertiary treatments. However, corrosion of mild steel and copper alloys was controlled within acceptable limits using the corrosion inhibitor tolyltriazole.

Cupronickel alloys are used as heat exchanger tube materials in nuclear power plant auxiliary coolant systems. In this work, the corrosion behaviour of cupronickel (70:30) alloy in permanganic acid medium was studied. Corrosion rate was found to follow logarithmic kinetics. Cyclic polarization studies showed that cupronickel did not undergo pitting in permanganic acid medium but uniform corrosion was observed. Presence of 0.43 mol/m 3 chromate in 2.5 mol/m 3 permanganic acid was found to decrease the corrosion rate of cupronickel by 50%. EIS and XPS studies revealed that the film formed on cupronickel was protective in nature and contained oxides of copper, nickel and manganese (mainly MnOOH). The composition of the film on cupronickel that had undergone chromate treatment also showed similar film except that it contained some chromium (III).

Nickel–aluminium bronze (NAB) alloys show good corrosion resistance under marine conditions. The corrosion behaviour of cast and wrought NAB alloys is illustrated in this work through a range of electrochemical techniques including open-circuit potentiometry with time, oxygen reduction voltammetry, NAB dissolution voltammetry, potential step (or flow step) current transients and linear polarisation resistance. The galvanic coupling of NAB to stainless steel or copper is examined by zero resistance ammetery. The importance of using controlled flow working electrodes is illustrated by the use of a rotating disc electrode, a rotating cylinder electrode and a bimetallic (NAB/copper–nickel) rotating cylinder electrode. In addition to controlling the hydrodynamics, such electrodes allow charge transfer data to separate from those of mass transport control under mixed kinetic control. Longer term seawater immersion trials on planar coupons coupled to titanium or cupronickel are also reported. The relative contributions of erosion and corrosion attack are considered using a wall-jet electrode and the corrosion characteristics of NAB are compared to those of copper and copper–nickel in chloride media.

The present work is concerned with the prediction of corrosion rates of copper and cupronickel in flowing seawater (up to 16 m per second) and for filmed copper and cupronickel up to 3.5 m per second). Such predictions are not available at present and would be of use for the design and maintenance of copper based components subjected to high velocity flows. Pipe systems on board ships often use such components-pumps, valves, elbows etc. The effect of flow on corrosion currents of filmed and polished samples that allows modelling of the behaviour of surfaces of old and newly fitted components is discussed. Equations describing the flow velocity dependence of these currents are developed and used to determine the mechanism controlling the copper dissolution and to identify the dissolution reactions.

The outer surface of thick oxides formed on the high copper-cupronickel alloys is invariably copper oxide, yet at room temperature the oxide film is entirely nickel oxide. The ESCA (or XPS) technique has been used to determine the temperature at which overgrowth of the initial nickel oxide by cuprous oxide takes place on a 60 40 alloy. By means of interrupted oxidation runs on a heated probe in the ESCA spectrometer, the physical and chemical displacement of Cu2O by NiO has been followed. It is concluded that the diffusion step in this displacement reatcion is probably rate controlling during oxidation of the alloy at temperatures up to 650°C. The XPS spectra have been interpreted quantitatively and excellent agreement is found between the calculated stoichiometry and the chemical shifts of the Auger spectra.