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AA5456-H116 undergoes accelerated localized corrosion when in a galvanic couple with cupronickel alloy C70600 (CDA 706) during ASTM G85 Appendix 2 Wet Bottom (G85 WB) testing. Surface and subsurface damage of AA5456-H116 and the region of protection of the C70600 were investigated and quantified after 31 d (124 cycles). These results were compared to finite element modeling results investigating relative humidity (RH) and water layer (WL) thickness. The best fit between experimental results and the modeling results was found when modeling assumed that a 3,000 μm water layer was formed during the spray portion at the start of each G85 cycle, with thinner water layers present during the decreasing RH portion of the cycle, which led to intergranular corrosion attack that was primarily focused in the proximity of the C70600/AA5456-H116 interface, but extending along the AA5456-H116 surface for some distance. The high-water layer thickness is likely the result of the corrosion product formation that traps additional electrolyte than would be present on a clean surface.

The hot tensile deformation properties and microstructure evolution of high purity C71500 cupronickel alloy at 1 023–1 273 K and 0.000 1–0.1 s−1 strain rates were studied by uniaxial hot tensile deformation method. Based on the experimental data, the flow behavior, microstructure and fracture characteristics of the alloy were analyzed after considering the influence of different deformation parameters. The relationship between microstructure and high temperature (T⩾1 023 K) plasticity is discussed, and the fracture mechanism is revealed. The relationship between strain rate sensitivity coefficient and stress index and plastic deformation is discussed. The constitutive equation of the alloy is established by Johnson-Cook model. Based on the dynamic material model, the energy dissipation model is established, and Prasad’s instability criterion based on Ziegler’s expected rheological theory is used to predict the unstable region in the processing map. Processing map in hot tensile is analyzed to provide theoretical basis for different processing technology.

The electron backscatter electron diffraction (EBSD) technique was applied to study the microstructure evolution and properties of the annealed cold rolling C71500 cupronickel alloy tube. The fixed reduction ratio of C71500 alloy tube was 23.71%. After rolling with different thickness reduction, the change process of grain, the evolution of texture, the characteristic distribution of grain boundary and the mechanical properties of the alloy tube were discussed systematically. The texture of cold rolling tube was obviously different from the drawing and sheet textures, and only the textures of RZ{111 type and R-cube{001} type could be observed after the two roller cold rolling process. After a certain amount of deformation, obvious accumulated orientation differences could be seen in the textures, which could create favourable conditions for the recrystallization nucleation. In the rolling process, the nonuniformity deformation of tube was caused by the inconsistency of stress state. With the increase reduction of tube wall, the tensile strength of the alloy increased from 405.13 to 574.65 MPa, the yield strength increased from 310.35 to 338.76 MPa, and the micro-Vickers hardness increased from 137.40 to 186.01.

The influence of sulfur on the hot compression properties of C71500 cupronickel alloy and the mechanism of thermo mechanical effect are studied for the first time. The composition of sulfide inclusions and its damage mechanism to properties were also studied. The effect of sulfur content on the dynamic recrystallization activation energy and the properties of the alloy was deduced and explained systematically. The relationship between the dynamic recrystallization activation energy and sulfur content was obtained, and a energy dissipation model was established based on the dynamic material model. The Prasad’s instability criterion was used to predict the unstable region in the processing chart. The effect of sulfur on the processing parameters selection was compared under different strain conditions, which could provide the ideal processing technology for the thermal deformation of C71500 alloy with various sulfur content.

Ultrasonic spot welding (USW) is a solid-state joining process which is preferably adopted in the joining of lithium-ion battery tabs for hybrid electric vehicles. It has several benefits o...

The present paper describes a failure investigation of 70/30 cupronickel tubes of a heat-exchanger that showed pinhole leakages and localized thinning after about 5 years of operation. The shell and tube type heat-exchanger contained demineralized water on the shell side which was cooled by seawater flowing in the tube side. The examination of failed and partially-thinned tubes were done using stereo microscope, optical microscope and scanning electron microscope equipped with energy dispersive spectroscopy. Formation of thick biofilms together with dense colony of bacteria were observed on the inner diameter surface of the tubes. The biofilms were concentrated just ahead of the tube inlet insert due to low flow conditions of seawater at these regions. The bacteria within the biofilm was identified as Acidithio bacillus thiooxidans type which are sulphur-oxidizing bacteria. Pits were observed to initiate under the biofilm which finally led to pinhole leakage. Therefore, localized thinning and pinhole leakage of the tubes were concluded to be due to microbiologically influenced corrosion. Recommendations to avoid such failures are also suggested.

Constitutive analysis for elevated temperature flow behavior of BFe10-1-2 alloy was carried out by using experimental stress–strain data from isothermal hot compression tests on a Gleeble-3800 thermo-mechanical simulator, in a wide of temperature range of 1,023–1,273 K, and strain rate range of 0.001–10 s−1. A constitutive equation based on double multiple nonlinear regression (DMNR) was proposed considering the independent effects of strain, strain rate, temperature and their interrelation. The predicted flow stress data obtained from the developed equation based on DMNR was compared with the experimental data. Correlation coefficient (R), average absolute relative error (AARE) and relative errors were introduced to verify the validity of the developed constitutive equation. The results showed that the developed constitutive equation based on DMNR could predict flow stress of BFe10-1-2 alloy with good correlation and generalization.

Morphology, dimensions, crystalline structure and compositions of nanomaterials are very critical in determining their unique characteristics. Here we report how the reducing agent concentration affects the surface morphology of copper nanowires and establish the optimized reaction conditions to synthesize high aspect ratio nanowires with a smooth surface. Also, reported is the magnetic field assisted technique to control the orientational and positional ordering of cupronickel nanowires (Cu/Ni NWs) on a large-scale area. A combination of magnetic field, surface derivatization and photolithographic techniques allowed self-assembly of Cu/Ni NWs into channels. The channel resistance as a function of the applied magnetic field during fabrication shows an anomalous decrease owing to the positional end-to-end alignment of NWs. Magnetic field and areal NW density dependence of NW sheet resistance in channels is presented and analyzed using scaling theoretical models.

The deterioration of metals under the influence of corrosion is a costly problem faced by many industries. Therefore, particle-reinforced composite coatings are being developed in different technological fields with high demands for corrosion resistance. This work studies the effects of nanoplatelet reinforcement on the durability, corrosion resistance, and mechanical properties of copper-nickel coatings. A 90 : 10 Cu-Ni alloy was coelectrodeposited with nanoplatelets of montmorillonite (Mt) embedded into the metallic matrix from electrolytic baths containing 0.05, 0.10, and 0.15% Mt. X-ray diffraction of the coatings indicated no disruption of the crystal structure with addition of the nanoplatelets into the alloy. The mechanical properties of the coatings improved with a 17% increase in hardness and an 85% increase in shear adhesion strength with nanoplatelet incorporation. The measured polarization resistance increased from 11.77 kΩ·cm2 for pure Cu-Ni to 33.28 kΩ·cm2 for the Cu-Ni-0.15% Mt coating after soaking in a simulated seawater environment for 30 days. The incorporation of montmorillonite also stabilized the corrosion potential during the immersion study and increased resistance to corrosion.

In this study, the characteristics of thin semi-rigid cables composed of different conductors and with outer diameters ranging from 0.86 to 1.19 mm were investigated at low temperatures. The thermal conductance was measured between approximately 1 and 8 K, and the frequency dependence of the attenuation in the cables was obtained at 3 K. The electrical conductors used in the cables were alloys: beryllium copper, brass, stainless steel (SUS304), phosphor bronze, cupronickel (CuNi), and niobium–titanium (NbTi). The thermal conductance of a commercial miniature coaxial cable with braided wires forming the outer electrical conductor was also examined for reference. The measured thermal conductance was compared to published data and that generated from material libraries and databases. Among the measured cables using normal metals, the semi-rigid cable composed of SUS304 conductors and a polytetrafluoroethylene insulator showed the lowest thermal conductance. The transmission performance of the semi-rigid cables using SUS304 or CuNi was improved by plating the central conductors with a silver coating of approximately \(3~{\upmu }\hbox {m}\) thickness, and their thermal conductance with the plating increased by approximately one order of magnitude. The superconducting NbTi semi-rigid cable exhibited the lowest thermal conductance of all the cables considered in the present study along with very small attenuation up to above 5 GHz.

High temperature deformation behavior of BFe10-1-2 cupronickel alloy was investigated by means of isothermal compression tests in the temperature range of 1,023~1,273 K and strain rate range of 0.001~10 s–1. Based on orthogonal experiment and variance analysis, the significance of the effects of strain, strain rate and deformation temperature on the flow stress was evaluated. Thereafter, a constitutive equation was developed on the basis of the orthogonal analysis conclusions. Subsequently, standard statistical parameters were introduced to verify the validity of developed constitutive equation. The results indicated that the predicted flow stress values from the constitutive equation could track the experimental data of BFe10-1-2 cupronickel alloy under most deformation conditions.

Cupronickel alloys, reinforced by L12 precipitates, offer a high strength, corrosion resistant and anti-bio fouling material for marine engineering applications. These alloys exhibit complex precipitate nucleation and growth mechanisms that must be fully understood in order to optimise the mechanical properties. In this work, the microstructural characteristics of the Cu-Ni-Al based alloy, Hiduron® 130, have been assessed in the as-received condition and following 100-h thermal exposures at 500, 600, 700 and 900 °C and after a two-stage exposure at 900 °C for 100 h followed by 500 °C for 100 h. The L12 phase was observed to precipitate both discontinuously and continuously and its subsequent coarsening was characterised alongside measurements of the lattice misfit. The hardness of the alloy was found to decrease with increasing exposure temperature up to the L12 solvus and correlated with the evolution of the L12 precipitates, the alloy grain size and the fraction of the discontinuously formed L12 phase.

Cupronickel alloys such as 70/30 Cu-Ni have excellent resistance to sea water corrosion and anti-fouling properties, and thus have been widely used for naval and offshore applications. Traditionally, arc welding and brazing processes have been used to weld such materials. In contrast, laser beam welding is a promising technology due to its high productivity, good process flexibility and reliability, and good welding integrity. In the present work, a high power fiber laser system is used to weld 5-mm thick 70/30 Cu-Ni alloy plates in a configuration of butt joints. Then, the laser welded joints are evaluated in terms of microstructures, defects, and mechanical properties (hardness, face and root bend, and tensile) in accordance with the applicable International Organization for Standardization and Defence Standard specifications. Keywords: Laser welding, Cupronickel alloy, Butt joint, Microstructure, Tensile properties, Bend testing

The performance of Benzotriazole (BTA) as a stress corrosion cracking (SCC) inhibitor is investigated for Cu-30Zn and Cu-27Ni alloys in Mattsson’s solution using electrochemical techniques and slow strain rate test (SSRT). With the addition of BTA, the polarization resistance increases for both alloys. Electrochemical impedance measurements show that BTA can form a protective film on the surface of the Cu-27Ni alloy and shifts the corrosion potential to nobler states. BTA also improves the corrosion resistance of the Cu-30Zn alloy by controlling the cathodic reaction rate and charge transfer resistance. SSRT results reveal that the presence of BTA decreases the susceptibility to SCC for both alloys; this improvement is more significant for Cu-27Ni alloy. Fractographic analysis after SSRT confirms that crack propagation regime is controlled by the BTA concentration. For Cu-27Ni alloy, fracture type changes from intergranular brittle to ductile as the protectiveness of BTA increases. Besides, BTA recovers the ductility by decreasing crack tip dissolution and growth as fewer cracks are observed around the necked area of fractured Cu-30Zn alloy tensile sample.

The present work aims to analyze the failure resulting from temperature change and its influence on the corrosion and fouling resistance of the cupronickel Cu-Ni 90/10 in simulated marine solution to predict the removal fouling temperature in the desalination heat exchanger and how affects fouling composition and morphology. The Cu-Ni 90/10 electrochemical behavior has been studied through: polarization tests, following the evolution of open circuit potential (OCP) and electrochemical impedance spectra (EIS) with immersion time under thermal and hydrodynamic conditions close to those prevailing in the heat exchanger of desalination industry. Electrochemical measurements show that the corrosion rate of Cu-Ni 90/10 alloy change with temperature, due to a competition between the formation of stable complexes on the metal surface and the dissolution of salts to generate aggressive ions in the corrosion medium. 60 °C ensures an equilibrium between the complexation reactions that promotes fouling stability, and fouling mitigation that leads to metal oxidation. In contrast, at high temperatures (80 °C), the dissolution of salts predominates over the complexation process. It can be deduced that 60 °C is a critical point for heat exchanger that promotes the formation of thin layer with low thermal fouling resistance that protects the installation against damage, maintain a good heat transfer and extend the cleaning scheduling of the machine. Surface analyses were performed by means Raman spectroscopy, SEM and EDS quantification, reveals the reinforcement of fouling by iron compound which make deposit more resistant at 60 °C.

The hot deformation behavior of BFe10-1-2 cupronickel alloy was investigated over wide ranges of deformation temperature and strain rate. The physics-based constitutive model was developed to predict the dynamic recovery (DRV) behavior of BFe10-1-2 cupronickel alloy at elevated temperatures. In order to verify the validity of the developed constitutive equation, the correlation coefficient (R) and average absolute relative error (AARE) were introduced to make statistics. The results indicated that the developed constitutive equation lead a good agreement between the calculated and experimental data and can accurately characterize the hot DRV behaviors for the BFe10-1-2 cupronickel alloy.

True stress and true strain data obtained from isothermal compression tests on a Gleeble-3800 thermo-mechanical simulator, in a wide range of temperatures (1073-1323 K) and strain rates (0.001-10 s−1), has been used to evaluate the material constants of two constitutive models: the modified Zerilli-Armstrong and the strain compensation Arrhenius-type models. Furthermore, a comparative study was conducted on the capabilities of the two models in order to represent the elevated temperature flow behavior of BFe10-1-2 cupronickel alloy. The suitability levels of these two models were evaluated by comparing the accuracy of their predictions of deformation behavior, correlation coefficient (R), average absolute relative error (AARE), relative errors of prediction, and the number of material constants. The results show that the predicted values of these two models agree well with the experimental values of BFe10-1-2 cupronickel alloy except at the temperature of 1123 K and the strain rate of 1 s−1. Meanwhile, the strain compensated Arrhenius-type model can track the deformation behavior of BFe10-1-2 cupronickel alloy more accurately throughout the entire temperature and strain rate range, while fewer material constants are involved in the modified Zerilli-Armstrong model.

The effect of different annealing times on microstructure and properties of C71500 cupronickel alloy tubes were studied at the temperature of 800 °C. Electron backscatter diffraction (EBSD) technique was applied to analyze the change trend of the “special” grain boundaries proportion of alloy under different processing conditions. The difference of microstructure transformation between small and large annealing deformation was analyzed. The optimal process was verified by means of grain cluster analysis, “Σ3 regeneration model” verification, the relationship between grain cluster size and grain size, and the residual stress analysis. The results show that the static recrystallization (SRX) is the main process of the 70.55% deformation alloy tube after annealing at 800 °C. With the increase of annealing time, the proportion of low coincidence site lattice (CSL) grain boundary has no obvious pattern change, but the grain size can be controlled. The static recovery is the main process for the small deformation (9.57%) alloy tube at 800 °C annealing, and the proportion of low ΣCSL grain boundary reaches 78.00% after annealing for 15 min. The ideal microstructure could be obtained by the two stages rolling processes: “70% deformation + 800°C annealing, holding for 20 min; and 9.57% deformation + 800°C annealing, holding for 15 min”.

The present paper describes a failure investigation of a tube that had shown leakage in a shell and tube type heat-exchanger with 70/30 cupronickel tubes and mild steel baffles (13 nos.). Corrosion damage or thinning of the failed tube was found to have occurred from the outer surface at all the baffle locations. Further examination of the failed tube was done using an optical microscope, a scanning electron microscope equipped with energy dispersive spectroscopy, Raman spectroscopy and an instrumented microhardness indentation machine for hardness measurement. Based on the results, it was concluded that the failure and the loss in wall-thickness of the tube at locations where it was in contact with the mild steel baffles were caused by fretting corrosion. The focus of this investigation is to bring out the metallurgical changes and the surface conditions (including changes in microstructure and microhardness, mode of corrosion attack and type of oxides/corrosion products) of the tube material undergoing fretting corrosion at micro level. Recommendations to avoid such a failure are also suggested.

Herein, we developed a straightforward and effective method to prepare epoxy coating for the early stage corrosion-detection of copper alloy. A selective “turn-on” chemosensor derived from rhodamine B for Cu(II), 3′,6′-Bis(diethylamino)-2-[[(2-hydroxyphenyl)methylene]amino]spiro[1H-isoindole-1,9′-[9H]xanthen]-3(2H)-one (RHS), was obtained via a two-step synthesis of acylation and schiff-base reaction. Both the colorimetric and fluorescent signals of the typical 0.5 wt% sensor-doped coating was observed, which showed that the area prior to corrosion was no significant damage. The concentration of RHS could be reduced to 0.14 wt%, after the zinc-based metal–organic framework (MOF) particle, ZIF-8, applied as a nanocontainer in this coating, and the detection sensitivity was better than the coating with bare RHS. This nondestructive strategy successfully realized early-stage corrosion detection for cupronickel in epoxy coating, which could be potentially used in the corrosion detections for copper alloys.

The effects of aluminum on the mechanical properties and corrosion behavior in artificial seawater of Cu-Ni-Fe-Mn alloys were investigated. Cu-7Ni-xAl-1Fe-1Mn samples, consisting of 0, 1, 3, 5, and 7 wt % aluminum along with the same contents of other alloying elements (Ni, Fe, and Mn), were prepared. The microstructure of Cu-7Ni-xAl-1Fe-1Mn alloy was analyzed by Transmission Electron Microscopy (TEM), and its corrosion property was tested by an electrochemical system. The results show that the mechanical and corrosion properties of Cu-7Ni-xAl-1Fe-1Mn alloy have an obvious change with the aluminum content. The tensile strength has a peak value of 395 MPa by adding 3 wt % aluminum in the alloy. Moreover, the corrosion rate in artificial seawater of Cu-7Ni-3Al-1Fe-1Mn alloy is 0.0215 mm/a which exhibits a better corrosion resistance than the commercially used UNS C70600. It is confirmed that the second-phase transformation of Cu-7Ni-xAl-1Fe-1Mn alloy follows the sequence of α solid solution → Ni3Al → Ni3Al + NiAl → Ni3Al + NiAl3. The electrochemical impedance spectroscopy (EIS) shows that the adding element aluminum in the Cupronickel can improve the corrosion resistance of Cu-7Ni-xAl-1Fe-1Mn alloy.

A theoretical model of infiltration kinetics based on the Darcy's law which was evaluated by W − Lambert function has been established for Cu-Ni-Mn alloy (grade MNMts 60-20-20) during melt infiltration into Cr3C2 porous skeletons with different morphology. It is shown, that theoretical calculations are in good correlation with experimental data obtained by pressureless infiltration of carbide preforms with open porosity 20-40 vol. % at 1200 °C. Calculations shows that infiltration height dependence on the average size of carbide particles is described by curves with a maximum which corresponds to~ 60 μm for specified system with carbide skeleton porosity of 40 vol. %. Key words: chromium carbide, manganese cupronickel, cermet, infiltration, Lambert W-function., Для процесу просочування пористих каркасів із Cr3C2 із різною морфологією сплавом Cu-Ni-Mn (марка МНМц 60-20-20) була розроблена теоретична модель кінетики просочування на основі закону Дарсі із використанням W- функції Ламберта. Показано, що теоретичні розрахунки з достатньо високою точністю описують експериментальні дані, які були отримані при просочуванні у вакуумі карбідних каркасів із відкритою пористістю 20-40 об.% при 1200 °С. Розрахунки показують, що залежність глибини просоченого шару від середнього розміру карбідних частинок описується кривою з максимумом, який для вказаної системи припадає на ~60 мкм при пористості карбідного каркасу 40 об. %.

The aim of this work was to form protective and durable films of octadecylphosphonic acid on the surface of CuNi alloy. In order to achieve this goal several parameters of the film preparation procedure were examined: temperature and duration of adsorption as well as the drying temperature. It was found that these parameters had significant impact on the corrosion protection efficiency and durability. The best corrosion protection was obtained when both adsorption and drying were conducted at elevated temperatures. The maximum protection efficiency was 96% for the first and 82% for the 14th day of exposure to corrosive medium.

The fabrication of uniformly interconnected cupronickel (CuNi) micromesh films on glass and polymer substrates with seamless junctions has been achieved using a simple transfer printing method. When used as a transparent heater, these CuNi micromesh films exhibited an effective and rapid heating performance at low input voltages (below DC 9 V) that can be attributed to the creation of a high quality network over the whole surface area that offers a relatively high transmittance, strong adhesion to its substrate and good mechanical flexibility. A high thermal stability and reliability was also observed relative to a pure Cu micromesh film. Transparent heaters based on CuNi micromesh are therefore considered suitable for providing anti-fogging or de-icing in optics and optoelectronic devices, as well as for wearable heating systems.

Purpose – The purpose of this study is to explore the influence of the sulfate reducing bacteria (SRB) on the corrosion of cupronickel. Design/methodology/approach – Tests monitoring the change in free corrosion potential, linear polarization resistance and electrochemical impedance spectroscopy and examination using the scanning electron microscope and energy spectrum analysis were used to investigate the corrosion behavior of cupronickel in blank medium and in media inoculated with SRB to explore the influence of the SRB on the corrosion behavior of cupronickel alloy. Findings – The results show that SRB can destroy the surface oxide film of cupronickel and significantly reduce the free corrosion potential and polarization resistance of the cupronickel, causing the cupronickel to corrode significantly. Originality/value – SRB are widely found in the water supply system and is one of the important factors inducing microbial corrosion. This paper verified that SRB promote cupronickel corrosion and explored the influence and mechanism of attack.

Corrosion fatigue performance of two copper alloys (admiralty brass and cupronickel 90/10) is investigated by conducting fatigue tests in artificial seawater. Two different experimental setups are developed and used: immersed rotating beam bending of round wires and immersed flexural cycling of rectangular plates. For the second setup, two sets of specimens are used: as-manufactured and after 1-year exposure to natural seawater in North Atlantic. In addition, the fatigue performance is compared between the dry and immersed tests. It is observed that the fatigue life of copper alloys in seawater environment depends on their composition and manufacturing parameters. Immersion in seawater does not affect low-cycle fatigue, however, high-cycle fatigue behavior shows significant differences. It is also observed that one-year preliminary exposure to natural seawater (stress-free corrosion) results in up to three times reduction of fatigue life at stress amplitudes corresponding to high-cycle fatigue.

The effects of room-temperature deformation on mechanical properties, the microstructure and texture evolution of continuous columnar-grained BFe10-1-1 cupronickel alloy tubes during room-temperature rolling and drawing were investigated. The results showed that continuous columnar grains were gradually thinned down into fiber microstructure, and the degree of working-hardening of the BFe10-1-1 alloy was increased continually with the increase of room-temperature reduction during rolling and drawing. After the rolling deformation degree of 82.8%, the ultimate tensile strength (UTS) of the BFe10-1-1 cupronickel alloy tubes increased to 418.7 MPa from 212.0 MPa of the as-cast state, and the elongation (El) of 8.5% was still obtained. The as-rolled BFe10-1-1 cupronickel alloy tubes were further drawn to the deformation degree of 99.0%, and the ultimate tensile strength (UTS) increased to 603.7 MPa and the elongation (El) reduced to 2.2%. The excellent room-temperature extensibility of the continuous columnar-grained BFe10-1-1 cupronickel alloy tubes is significantly beneficial from the relative high volume fraction of the texture as well as low angle boundary.

The drawing of 12X18H10T stainless-steel wire with a cupronickel coating and cadmium-plated carbon-steel wire is considered. The quality of zinc-plated carbon wire is shown to depend on the drawing temperature, which must be stable.

With the rapid development of the shipping and the power industry, the demand for high-performance cupronickel alloy pipes is greatly increasing. The main processing methods of this alloy include semisolid ingot casting and deformation by hot extrusion. Many defects appear during the hot extrusion process for large diameter cupronickel alloy pipes, which results in considerable problems. Therefore, numerical simulation of hot extrusion for cupronickel alloy pipes before the practical production is of vital significance to properly determine the deformation parameters. In order to obtain the influence of processing parameters on the piercing extrusion process of large diameter cupronickel alloy pipe, metal flowing law under different deformation conditions was simulated and analyzed via employing a 3D FEM code. The results showed that piercing speed had no obvious influence on the cupronickel alloy billet. However, the friction had significant influence on the piercing process of cupronickel alloy billet: with the increase of friction coefficient, the temperature and the load increased.

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.

PurposeThe purpose of this paper is to investigate the effect of iron content (2% and up to 6% Fe) on the corrosion behavior of 90Cu‐10Ni alloys in 3.5% NaCl at different temperatures (23, 50 and 80°C) under stagnant conditions and fluid flow (with an agitation speed of 350 and 900 RPM). The laboratory study was conducted following a failure of high iron content (up to 6%) 90Cu‐10Ni heat exchanger tubes in a desalination plant.Design/methodology/approachPotentiodynamic polarization measurement (DC) was used to estimate the corrosion rate of the 90Cu‐10Ni alloys in NaCl solutions under stagnant and fluid flow conditions.FindingsIt was found that the higher iron content cupronickel material suffered higher corrosion rates in all tests. The intensity of the corrosion attack of both materials was increased significantly with increasing experimental temperature or flow velocity. The results support a previous prediction that the presence of excess iron (well above 2%) has played a major role in corrosion failure of 90Cu‐10Ni heat exchanger tubing material in seawater.Originality/valueThis paper explains the role of iron content on the corrosion behavior of 90Cu‐10Ni alloys in 3.5% NaCl under stagnant and fluid flow conditions.

A cupronickel heat exchanger failed after 10 years of service. The cooling heat exchanger was in service in a marine environment, with water flowing along shellside and natural gas along tubeside. Many tubes showed leakages during a regular maintenance test. A comprehensive failure analysis of the heat exchanger revealed the de-nickelification process on the external side of the damaged tubes (shellside). The de-nickelification originated from a large deposit of sea water scale, over tube lengths, which completely covered the area just outside the internal portion of the tubesheet, and occurred because of a failure of the regular cleaning operation. Stagnant water and possible hot spot formations on the tubes probably caused the phenomenon.

Corrosion inhibition of Cu–30Ni alloy in aerated 0.5 M H2SO4 solution by cysteine, an amino acid, has been investigated. Potentiodynamic polarization and impedance spectroscopy (EIS) at open circuit potential were performed. Corrosion current density was also determined from colorimetric experiments. Voltammetric curves showed that cysteine addition to 0.5 M H2SO4 affects largely the cathodic process; shifting the corrosion potential to more negative values and decreasing significantly the corrosion current density. The inhibiting efficiency reaches a value of 91% at an inhibitor concentration of 10−3 M. Impedance data reveal the adsorption of the inhibitor and the surface relaxation process due to nickel. Polarization resistance deduced from impedance measurements or voltammetric experiments are in a good agreement.

Pin-hole leakage was observed in a number of 90/10 cupronickel evaporator tubes of a chilling plant which was in service for about 6 years. Chilled water is cooled from 12 °C to 7 °C which flows inside the evaporator tubes, while the OD side has LiBr environment. The failure investigation of the failed tubes revealed greenish/blackish uniform deposits together with some spots where localized thick deposits on the ID surfaces were present. Underdeposit corrosion beneath these thick deposits was the primary reason for failure of the tubes. Intergranular corrosion was also observed underneath the thick deposits. The ID surface of the failed tubes confirmed the presence of wide variety of deposits, e.g. carbonates, silicates, phosphates, and sulphur-bearing compounds. The stagnant conditions under the thick deposits alter the chemistry inside the crevices thus formed. The altered chemistry conditions caused rapid corrosion (and intergranular attack) on the cupronickel tubes. Remedial measures that may be undertaken to prevent future occurrence of the problem are addressed.

Copper nickel alloys 90/10 and 70/30 are used extensively in saltwater systems operating on marine platforms and offer high corrosion and biofouling resistance. However, systems using these materials were reported to fail prematurely. Preliminary investigations revealed pollution of harbor waters with tangible levels of ammonia and sulphides which was reported to be the primary cause of failure. The present author(s) have performed laboratory and field investigations to identify the stress-material-environment interaction of the copper nickel alloys extensively in use on seawater system of marine platforms. Results obtained point to the fact that polluted seawaters can affect the material properties of the alloy leading to premature failure(s) of systems at stresses well below the designed stress. The paper presents the correlation of the results of the laboratory and field tests of 90/10 and 70/30 copper–nickel alloys in seawaters polluted with ammonia and sulphide pollutants.

PurposeThe purpose of this paper is to evaluate the effect of seawater temperature on the corrosion behaviour of 90‐10 cupronickel alloys. Also, to investigate the effect of thiosulphate additions (one of the major sulphide oxidation products in seawater) on the alloy corrosion rate in seawater.Design/methodology/approachPotentiodynamic polarization measurement (DC) was used to estimate the corrosion rate of the cupronickel alloy in seawater with and without thiosulphate species (50‐650 ppm).FindingsIt was observed that the cupronickel alloy suffered accelerated corrosion as the seawater temperature was raised from 25 to 50 or 80°C. The increase in the corrosion rate was found to correspond well with the negative shift in the free corrosion potential. Thiosulphate addition was found to depend on the test temperature. At 25°C, thiosulphate activated the alloy dissolution rate and the higher were the thiosulphate concentrations, the higher was the corrosion rate. At 50 or 80°C, however, thiosulphate promoted the dissolution rate at early stages, but seemed to interfere with the surface film formation later on, producing a black film that effectively decreased the alloy corrosion rate. At higher potentials, however, the film became non‐protective, leading to accelerated corrosion once again.Originality/valueThis paper explains the corrosion behaviour of 90‐10 cupronickel alloys in seawater as a function of test temperature and thiosulphate additions.

The failure of 90/10 cupronickel heat exchanger tubes in hydrogen coolers were seen after few years in use. The tubes had river water flowing at a velocity of 2.5 m/s. The shell side was exposed to hydrogen at a pressure of 3.5 kg/cm2. The inlet and outlet temperature of the cooling water of the cooler are 37 °C and 47 °C, respectively. The failures were pin hole type with a thick layer of muck deposit on the inner side of the tube. The metallographic studies carried out for the tube showed a well annealed microstructure. The region near the pit showed attack along the grain boundaries with dislodging of the grains. The electron probe micro analysis (EPMA) studies revealed the denickelification near the pits. The energy dispersive spectroscopy (EDS) analysis of the pit showed the presence of copper chloride and also the variation in the copper and nickel concentration with respect to the unaffected regions of the tube. Microbial presence was detected in the water as well as the muck deposits in the tubes. The pin hole failure of the tube was a result of the combined action of the chloride as well as the deposits in the tube which gave a conducive environment for the microbial activity to flourish which has caused the propagation of the pit through intergranular corrosion.

The reserves of chromonickel ore in Kazakhstan and around the world are briefly reviewed. Research on the enrichment and pelletization of chromonickel ore and the smelting of chromonickel hot metal using different reducing agents is reported.

Cupronickel pipes are widely used in cooling systems. Under this application, localized corrosion is observed, particularly associated with selective corrosion of nickel (denickelification). This work studied the denickelification process in solution-treated cupronickel alloys 90-10 (Cu-10wt%Ni), with aluminum and iron additions, in 0.01 M, 0.1 M, or 0.6 M sodium chloride (NaCl) aqueous solutions. Polished surfaces of the studied materials were submitted to potentiodynamic polarization, and after that, the polarized surfaces were studied using optical microscopy (OM) and scanning electron microscopy (SEM) assisted by energy-dispersive spectroscopy (EDS). A passivity break potential (Epb) was determined in all solutions, related to the initiation of selective corrosion of nickel. When submitted to cyclic potentiodynamic polarization, alloys with higher Epb showed the higher nickel losses in localized spots. However, potentiodynamic polarization tests conducted in 0.01 M NaCl until current densitie...

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).

Failure analysis of cupronickel condenser tubes of a crude distillation unit of a petrochemical refinery has been conducted. Condenser tubes carrying sea water were found to undergo premature failure which was preceded by extensive overall thinning, formation of shallow channels, pits, etc., and greyish-black internal deposits in one of the units. In the other unit, the failure of tubes was noticed without any significant overall thinning and in the presence of adherent, hard and black-brown deposits. The studies indicated that the increased velocity of sea water as well as the deficiency of iron in the alloy had resulted in failure in one case whereas relatively low velocity of water associated with deposition of sludge and bio-fouling were the causes of failure in the other case. The failure of tubes could be controlled by maintaining the water velocity within a specified range, flushing the tubes with clean water, use of anti fouling paints, selecting a more appropriate composition of the cupronickel alloy, through control of sea water sulphur level, etc.

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 authors carried out failure analysis of bent and branched copper-nickel alloy pipelines that had failed in marine environments. These failures were almost always dominated by a brittle stress-corrosion cracking (SCC) mode and could often be attributed to the presence of ammoniacal byproducts in the operating environment. Attempts were made to reproduce the marine-type field failures in the laboratory by testing a Cu-5.37%Ni alloy, similar to the material used in failed pipelines. The tests were performed under slow strain rate test (SSRT) conditions in aqueous ammonia and ammoniacal seawater. Results revealed that the ammonia-induced brittle SCC failures were predominant and reduced the load-bearing capacity of the alloy. The real-life failures are not simple SSRT-type failures. The operating conditions, in addition to the induced residual stresses from manufacturing/processing, subject the system pipes to external forces and widely varying pressures and fluid flow rates. This combination of stresses can produce both static and cyclic stress conditions, similar to a static load coupled with a low-amplitude cyclic load. Tests conducted under superimposed cyclic stresses on prestressed specimens were found to accelerate the stress-corrosion failures in the present copper-nickel alloy in an ammoniacal environment.

In this study, the corrosion behavior of 90%Cu-10%Ni (C70600) cupronickel alloy in artificial seawater was investigated. The corrosion tests were conducted using a rotating cylindrical electrode at different speeds. In the experiments, free corrosion potential tests, electrochemical impedance spectrum (EIS) analysis, weight loss tests, and optic microscope observation were performed. The corrosion rate of 90%Cu-10%Ni alloy in artificial seawater increased with increasing rotation speed and time. Damage period was changed with rotation speed. It was also determined that the damage to the protective film began after 3 hours at the rotation speed of 1600 rpm, and after 3 hours at 2000 rpm, and increased with increasing time. It was determined that 1200 rpm rotation speed is better than both 1200 rpm and 1600 rpm for working conditions.

All the Arabian Gulf States suffer from a shortage of fresh water resources. This deficiency is remedied through the desalination of seawater, mainly by the multi- stage flash (MSF) evaporation technique. The number of MSF distillers in Abu Dhabi is 382, producing a total quantity of 5,465,784 m 3 /d of potable water. It has been reported that these units have a tendency to suffer, at varying degrees, from a variety of corrosion and scaling problems. This paper consists of two sections. The first section describes some of the corrosion problems facing the desalination plants, concentrating mainly on the vapour-side corrosion (VSC) of condenser tubes made of cupronickel alloys, 70/30 and 90/10. The research in this section is necessary because condenser tubes are the part most prone to failure in desalination plants. Almost all of the previous cases of corrosion of condenser tubes reported were focused on water-side corrosion of the tubes. The present paper will discuss two contrasting cases of attack related to both acidic and alkaline corrosion in the vapour side. This is the first such research to be cited anywhere in this field. The second section of the paper will discuss the mechanism of the scale formation reported in the literature, and will present the actual scale formed in desalination plants, which is different from scale formed in the laboratory.

Cupronickel alloys have been extensively used in marine and offshore applications. These alloys offer desirable physical and mechanical properties to be used as a versatile engineering alloy. The oxidation resistance of these alloys was due to the formation of scales consisting of a thick, inner Cu2O layer and a thin, outer CuO layer, together with nickel rich internal oxide. These alloys are superior to bronzes in their corrosion resistance but fail under oxidizing conditions. In sulphide atmospheres they undergo sulphidization. Depending upon the alloy composition, they form layers consisting of alloy/nickel sulphide/CuS of various proportions. In chloride solutions, they undergo localized attack. For lower chloride concentration, an increase in nickel content worsens the resistance to passive film breakdown, where as for higher chloride concentration an increase in the nickel content favour passivation. In seawater, the prime source is dissolved oxygen and the corrosion product is Cu2O. This is formed by the hydrolysis of CuCl2-. The use of ozone enhanced the dissolved oxygen content. Localised attack occurred at those points where the seawater is in motion. The impingement and general corrosion resistance was improved by the addition of iron in the alloy. Sulphides and ammonia as pollutants adversely influenced the performance of the alloy. Microbial adhesion alters the protective properties of the complex layers of the alloy. The bacteria enhanced the corrosion rates in seawater with intergranular corrosion and denickelification. The minor additions of an element, use of inhibitors in the medium and cathodic protection are the main methods of corrosion control in aqueous media. The various aspects of the corrosion resistance behavior of cupronickel alloys in different environments are discussed in the review

In this work the mechanical properties of a highly alloyed cupronickel have been analyzed using a neural network technique within a Bayesian framework. In this way the mechanical properties can be represented as an empirical function of the compositional variables. This method has been used to analyze the relative contributions of the various elements to the mechanical properties. Whilst the method is entirely empirical, it will be shown that the predictions made are of metallurgical significance.

The results of the 2nd VAMAS measurement intercomparison program on low-frequency (hysteretic) a.c. loss are presented and discussed. Two sets of multifilamentary NbTi strands (Set No. 1: copper matrix, fil. diams 0.5, 1, 3, and 12 μm; Set No. 2: cupronickel matrix, fil. diams 0.4, 0.5, and 1 μm) were subjected to interlaboratory testing. In an initial series of tests, samples in various forms (e.g. wire bundles, coils) were measured mostly by vibrating-sample- and SQUID magnetometry. Considerable scatter was noted especially in the small-filament-diameter a.c.-loss data. In a study of measurement accuracy, a supplementary series of tests compared the results of VSM measurement of a given pair of copper-matrix samples. In the light of all the results, factors contributing to a.c. loss error are discussed and recommendations are made concerning the specification of future a.c.-loss measurement intercomparisons.

The article summarizes results of part of the second VAMAS a.c. loss measurement intercomparison. This program was carried out at 17 participating laboratories on two sets of multifilamentary NbTi strands (Set No. 1: copper matrix, fil. diam. between 0.5 and 12 μm; Set No. 2: cupronickel matrix, fil. diam. between 0.4 and 1.2 μm). The results reported here were measured by means of a.c. magnetization methods and separated into hysteresis and coupling losses. One laboratory used a calorimetric method. The data scatter in measured hysteresis losses among the participating laboratories was reasonably small for different measuring methods adopted and experimental arrangements used. On the other hand, the data scatter in coupling losses was large, mainly because in most laboratories a.c. losses were measured only at low frequencies (below 1 Hz), where the separation of coupling losses from total losses tends to be inaccurate. The comparison of measured hysteresis losses with the critical state model showed a large disagreement, which is assumed to be due to proximity effect coupling between filaments. © 1997 Elsevier Science Limited