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Cupronickel alloys have been broadly utilized in various fields due to their excellent properties. In this paper, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) curves were used to study the impact of different Mn contents on the corrosion resistance of 90/10 cupronickel alloy. Surface morphology, electronic structure, and phase composition of the film formed on different Mn content 90/10 cupronickel alloy immersed in 3.5% NaCl solution for 30 days were investigated using SEM, EDS, Mott–Schottky, XRD, XPS, etc., revealing that adding an appropriate amount of Mn to the 90/10 cupronickel alloy can change the corrosion resistance of the alloy. The corrosion resistance first increases and then decreases with the addition of Mn content. Among them, the sample with 0.87% Mn addition has the best corrosion resistance, the corrosion product film is more complete, no cracks appear, and the corrosion product binding force is stronger. The addition of Mn promotes the filling of cation vacancies by Ni and generates more NiO, which enhances the stability of the corrosion product film.

Spray coating formation of stearic and octadecylphosphonic acid films for corrosion protection of cupronickel alloy was studied in this work as a more practical alternative to widely studied dip-coating method. Protective properties of organic films formed under various experimental conditions were examined by electrochemical studies in 3% NaCl solution as a corrosive medium. Polarization resistance measurements as well as electro­chemical impedance spectroscopy were employed to follow in time the corrosion behaviour of cupronickel alloy modified by studied organic acids. It was found that among examined experimental parameters, time elapsed between two sprays and number of sprays have the strongest influence on the film stability and its protective properties. This study confirmed that it is possible to form by spray coating the films of stearic and octadecyl­phosphonic acid with protective properties that resemble to those of the films prepared by dip-coating method. Differences in corrosion behaviour of samples protected with stearic and octadecyl­phosphonic acid were attributed to difference in the bond strength between substrate and each organic acid. Studied samples were also examined by the scanning electron microscopy. Fourier transformed infrared spectroscopy studies showed that crystalline structure dominates in studied films, while contact angle measure­ments confirmed that modified cupronickel alloy surface exhibits hydrophobic properties.

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.

An environmentally benign and facile bilayer coating comprised of graphene oxide (GO) and acrylic polymer is fabricated over cupronickel sample using electrophoretic deposition followed by dip coating. The infrared, Raman, and field emission scanning electron microscopy (FESEM) studies of the bilayer coating confirm the noncovalent functionalization of GO through H-bonding with acrylic polymer, reduction in local defects in GO structure, and distorted spherical void peripheries of polymer coating, respectively. The FESEM cross-sectional analysis showed that the coating thickness is 5–6 µm. The bilayer-coated sample showed a three- to fourfold increase in the corrosion resistance, as compared to GO-alone-coated sample in 3.5% (w/v) NaCl electrolyte, which is attributed to the reduction in the local defects in GO coating and the galvanic coupling between the GO and sample surface. The GO sheets make the diffusion pathway of corrosive media more tortuous for corrosive ions to reach the metal surface. The lower anodic current density observed with the new bilayer coating after 30 days of exposure confirms the active corrosion protection. The coating was intact and stable after 30 days of exposure in chloride medium with a water uptake of about 32.7%.

A laboratory investigation has been achieved to study the effect of flow velocity on the corrosion behaviour of Cu–Ni 90/10 alloy immersed in synthetic seawater, at 60 °C which simulates the real condition of desalination industry in the south of Tunisia. Flow velocity was one of major parameters influencing the oxidation process of cupronickel pipe, through its effect on mass transport and corrosion rate. This influence has been examined on a laboratory scale by means of electrochemical techniques like: Potentio-dynamic polarization, electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR). Results show that the flow velocity has a significant influence on corrosion rate, compared to static immersion. This effect was confirmed by means of corrosion current density (icorr) increase and polarization resistance Rp decrease with exposure time, as indicated by LPR and EIS measurements. Corrosion was attributed to the film deterioration by the erosion corrosion phenomena, caused essentially by hydrodynamic conditions. Indeed, at stagnant condition, the substrate proves a higher corrosion resistance due to the stability of the protective layer.

Cupronickel B10—an important material widely used in the aero industry—has excellent mechanical and physical properties, such as corrosion resistance and ductility. The present study conducted a quasi-static test and split Hopkinson pressure bar (SHPB) test to obtain the quasi-static and dynamic mechanical properties of cupronickel B10, respectively. In these two experiments, the parameters needed for material constitutive models in cutting simulation are derived. However, the impact deformation temperature in the SHPB experiment has long been ignored, resulting in insufficient simulation accuracy. Hence, the impact deformation temperature is referenced to modify material constitutive models. Simulation results of the models are validated in orthogonal cutting experiments. Validation shows that Johnson-Cook class models are superior in simulating the chip form while Drucker-Prager class models are suitable for forecasting the cutting force and temperature. In particular, modified Drucker-Prager models can reduce the error of cutting force FC to 18.01 %.

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.

The corrosion behavior of cupronickel alloy immersed in the simulated seawater in or without the presence of sulfate-reducing bacteria (SRB) was studied. The results of scanning electronic microscopy and electrochemical impedance spectra reveal that corrosion of the sample immersed in the simulated seawater with SRB was more serious than that immersed in the simulated seawater without SRB. The atomic force microscopy images show that after immersion for 15 days, the surface roughness of the sample in the simulated seawater with SRB was higher than that of the sample in the simulated seawater without SRB. The analysis of confocal laser scanning microscopy indicates that the average depth of the pits on the surface of the sample in the simulated seawater with SRB was almost twice deeper than that of the sample in the simulated seawater without SRB.

Cupronickel B10—an important material used in aircraft carriers—exhibits excellent electrochemical and mechanical properties, such as high corrosion resistance and weldability. The Split-Hopkinson pressure bar (SHPB) test is a classical method to obtain the dynamic mechanical properties of solid materials. However, the deformation temperature has long been ignored in SHPB studies, which results in low accuracy of the material constitutive model. Thus, in this study, a new method for obtained the deformation temperature was proposed and the modified material equation was validated using experimental data. Quasi-static compression and SHPB experiments were conducted with a thermocouple. The results revealed that the deformation temperature of the quasi-static tests was nearly zero, whereas that of the SHPB experiments ranged from 40 to 90 °C. Therefore, the method developed to describe the deformation temperature can be used to improve the precision of SHPB experiments, as demonstrated for the case of cupronickel B10.

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 composition of seawater plays a very significant role in determining the severity of corrosion process in marine assets. The influential contributors to the general and pitting corrosions in marine structures include temperature, dissolved oxygen (DO), salinity, PH, chlorides, pollutants, nutrients, and microbiological activities in seawater. The Cu-Ni (90/10) alloy is increasingly used in marine applications such as heat exchangers and marine pipelines because of its excellent corrosion resistant properties. Despite the significant advancements in corrosion shielding procedures, complete stoppage of corrosion induced metal loss, especially under rugged marine environments, is practically impossible. The selection of appropriate metal thickness is merely a multifaceted decision because of the high variability in operating conditions and associated corrosion rate in various seawater bodies across the globe. The present research study aims to analyze the early phase of corrosion behavior of Cu-Ni (90/10) alloy in open-sea conditions as well as in pollutant-rich coastal waters of the Arabian Sea. Test samples were placed under natural climatic conditions of selected sites, followed by the mass loss and corrosion rate evaluation. The corrosion rate in the pollutant-rich coastal waters was around five times higher than in the natural seawater. A case study on marine condenser (fitted with of Cu-Ni 90/10 alloy tubes) is presented, and a risk-based inspection (RBI) plan is developed to facilitate equipment designers, operators, and maintainers to consider the implications of warm and polluted seawater on equipment reliability, service life, and subsequent health inspection/ maintenance.

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.

In this study, the gradient grain induced by punching deformation and recovery treatment on a cupronickel alloy surface sample were investigated, and their effects on corrosion resistance were measured by atom force microscopy (AFM), X-ray diffraction (XRD), electrochemical measurement, electron work function (EWF), and contact electrical resistance (CER). The cupronickel alloy surface experienced punching deformation for 60 min and recovery at 300 °C for 1 h to produce gradient surface. The grain size measured by XRD is bigger than that measured by AFM, due to X-ray intensity of 95 % produced at the depth of 12–20 μm for the crystal planes of (111), (200), and (220). The gradient grain surface, compared to the original surface, shows a 13.7-fold decrease in passivation current density (i p), and corrosion potential (E C) increases by approximately 9.8 %. These results are attributable to the increase in EWF and formation of passivation film with better adhesion and compactness after treatment.

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.

Self-assembly of organic molecules onto metallic surfaces is an efficient way to modify surface properties of metallic materials. The aim of this paper was to examine the possibility of improving the corrosion stability of copper nickel alloy in chloride environment by self-assembled films of palmitic and stearic acid. Electrochemical techniques such as potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were used to determine the protective properties of the fatty acids films. Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM) and contact angle (CA)measurements were used to evaluate structural properties of the surface layers. It was found that even a small difference in a fatty acid chain length might have a strong effect on layer stability in aqueous medium.

The paper describes an experimental study concerning the influence of major environmental parameters (temperature, chloride, carbon dioxide, and oxygen) on the corrosion behavior of 90/10 Cu–Ni alloys widely used for heat-transfer tubes. Electrochemical techniques have been used to investigate the corrosion behavior of 90/10 Cu–Ni alloys in aerated 3.5% NaCl solutions, at temperatures of 25, 50, and 80°C with and without the injection of carbon dioxide. The results have revealed increases in chloride corrosion rates of the 90/10 Cu–Ni alloy with temperature and decreases with CO2 presence. Tests performed in aerated chloride–CO2 solutions have shown higher corrosion rates relative to those conducted in deaerated chloride solutions saturated with CO2 species. The surface morphology of polarized specimens in chloride solutions with and without CO2 presence has shown a susceptibility to pitting attack. Pit characteristics have been found to be highly influenced by CO2 presence.

Copper-nickel alloys are extensively used in marine applications and in desalination plants (Sherif et al. in Colloid J Interface Sci 311:144, 2007; Sherif and Park in J Electrochim Acta 51:4665, 2006) because of their good electrical and thermal conductivities, mechanical properties, corrosion resistance, and ease of fabrication of the equipment (Revie in Uhlig’s corrosion handbook. Wiley, New York, p. 729, 2000).

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 aim of the present study was to determine the aggressiveness of groundwater samples towards corrosion of various commercially important metals and to study the correlation between theoretical and experimental values of corrosiveness. For this purpose, 20 groundwater samples were collected in different mandals of Krishna District, Andhra Pradesh, India, and the metals selected were carbon steel, aluminium, copper and cupronickel alloy. The corrosiveness was determined by using gravimetric measurements. Further, corrosion and scaling indices, namely Langelier index (LI), aggressive index (AI), Ryznar index (RI), Puckorius index (PI) and Larson–Skold index (LS), were calculated with the help of various water quality parameters of all the samples to estimate their corrosivity. The experimental values of corrosion rates were attempted to correlate with various indices calculated and quality parameters determined in case of all the samples. It is observed that there is a significant lack of correlation between the indices and corrosion rates. Among the five indices taken into account, LI, AI and RI indicate scaling tendency of water samples, as inferred by their mean values, 0.657, 12.576 and 6.612, respectively, while the other two indices, PI and LS with the mean values of 8.141 and 1.188, respectively, suggest the corrosive behaviour. Further, the mean values of correlation coefficients, 0.18 and 0.27 for PI and LS, respectively, are higher compared with those for LI, AI and RI. The mean values of correlation coefficients of dissolved oxygen, chlorides and electrolytic conductivity are 0.33, 0.25 and 0.25, respectively, which are relatively higher compared with those of other quality parameters. The probable reasons for low correlation coefficients are explored based on the statistical data. Also, it was concluded that one of the significant factors, namely dissolved oxygen which has strong influence on corrosion of metals, was considered in none of the indices, leading to very low correlation between the theoretical and experimental values of corrosiveness.

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.

The application performances of TA2 titanium\S44660 super ferrite stainless steel\B30 cupronickel, which are widely used in power plant, were researched using electrochemical test and mechanical test. The results show that corrosion resistance of B30 is significantly lower than TA2 and S44660. Besides, corrosion resistance of S44660 is superior to TA2. Yield strength and tensile strength of S44660 is higher than TA2 and B30. When considering thickness of cooling tubes, flow rate of cooling water and clean coefficient, the thermal conductivity of three materials have little differences. The shock resistance of S44660 is better than TA2 and B30. S44660 contains a small amount of Ni, which improves greatly the anti-cracking ability of the base metal and welding bead.

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.

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.

Corrosion of the metal oxide surface of cupronickel (CuNi) alloys is a problem in applications such as household water pipes, industrial pipelines, and marine vessels. On other substrates, thin films have been used as barriers to corrosion. Here, the formation of self-assembled monolayers (SAMs) on the CuNi metal oxide surface has been investigated. Stable, well-ordered SAMs of octadecylphosphonic acid (ODPA) and 16-phosphonohexadecanoic acid (COOH-PA) were formed on the metal oxide surface of CuNi foils (55% Cu/45% Ni) using a solution deposition method. The ODPA modified surfaces could be used to provide a non-reactive barrier that inhibits corrosion of the CuNi metal oxide surface. Meanwhile, COOH-PA films could be used for further surface reactions such as surface initiated polymerization, in which polymer coatings are grown directly from a well-ordered film. Film-modified surfaces were characterized using diffuse reflectance infrared Fourier transform spectroscopy, contact angle analysis, and matrix assisted laser desorption ionization time of flight mass spectrometry. The ability of the films to inhibit corrosion by limiting oxidation of the CuNi surface was assessed using cyclic voltammetry.

An instantaneous corrosion rate (ICR) monitoring technique, suitable for application in recirculating cooling water systems, is useful for rapid appraisal of corrosiveness of the aqueous system with respect to metal and metal alloys of interest. In this study the instantaneous corrosion rates of mild steel, copper, and cupronickel alloys were measured at various times during an exposure period by electrochemical polarization resistance measurements using a three-electrode system. The average corrosion rates (ACR) were also determined by the gravimetric weight loss method to correlate with the ICR data. Stainless steel was used as the reference electrode to replace the standard saturated calomel electrode for increased robustness of the system in pilot-scale cooling systems. A side-streamflow channel unit was designed to hold the three electrodes in flowing cooling water. Use of stainless steel as a reference electrode was reliable and ICR was monitored intermittently for 28 days. Integration of the ICR data from the pilot-scale cooling towers correlated well with the ACR results, with similar correlation coefficients obtained from bench-scale experiments.

A novel hydrophobic film was prepared by Stearic acid (SA) chemically adsorbed onto the cupronickel B30 surface. The film properties were characterized by means of water contact angle measurement and electrochemical techniques. The results indicate that the structure of the adsorbed film is hydrophobic, and the contact angle is 113.82° for water. AC impedance and polarization curve measurements show that the corrosion resistance of cupronickel B30 modified by stearic acid is improved remarkably, and the inhibition efficiency reached 66.85%. After hydrophobic modified by stearic acid, the inhibition efficiency could reach 88.85% in 3% NaCl solution with the concentration of 0.1 g/L Na2WO4.

Passively treated abandoned mine drainage (AMD) is a promising alternative to fresh water as power plant cooling water system makeup water in mining regions where such water is abundant. Passive treatment and reuse of AMD can avoid the contamination of surface water caused by discharge of abandoned mine water, which typically is acidic and contains high concentrations of metals, especially iron. The purpose of this study was to evaluate the feasibility of reusing passively treated AMD in cooling systems with respect to corrosion control through laboratory experiments and pilot-scale field testing. The results showed that, with the addition of the inhibitor mixture orthophosphate and tolyltriazole, mild steel and copper corrosion rates were reduced to acceptable levels (< 0.127 mm/y and < 0.0076 mm/y, respectively). Aluminum had pitting corrosion problems in every condition tested, while cupronickel showed that, even in the absence of any inhibitor and in the presence of the biocide monochloramine, its corrosion rate was still very low (0.018 mm/y).

Minor Fe additions are widely added to enhance the corrosion resistance of cupronickel alloys. The present paper aims at optimizing the amounts of Fe in Cu 70 (Ni,Fe) 30 (at.%) alloys using a cluster-plus-glue-atom model for stable solid solutions. By this model, it is assumed that one Fe atom and 12 Ni atoms formed a Fe-centered and Ni-surrounded cube-octahedron cluster and the isolated FeNi 12 clusters embedded in a Cu matrix. The stable solid solution alloy composition of Fe-modified Cu 70 Ni 30 alloy was described by a cluster formula [Fe 1 Ni 12 ]Cu 30.3 = Cu 70 Ni 27.7 Fe 2.3 (at.%). The effect of homogenizing annealing treatment on the microstructure and corrosion resistance was also investigated by XRD, TEM and electrochemical corrosion measurements. The corrosion test indicates that the Cu 70 Ni 27.7 Fe 2.3 alloy annealed at 800 °C for 5 h possesses the best corrosion resistance in 3.5% NaCl solution.

This paper presents finding of a failure investigation on a heat exchanger tubes in a desalination plant. Fabricated from Type 90-10 copper-nickel alloy, the tubes experienced sever corrosion after one year of operation. Leaks were observed due to pitting attack requiring repairs and eventual replacement of the cupronickel tubes. The cause of the failure was determined by conducting a physical inspection, and performing macro and micro examinations. The failure of the tubes was mainly attributed to the high iron content (up to 6%). The results of the failure investigation are discussed along with corrosion issues that were identified in the associated heat exchanger tubes.

The gravimetric weight loss method and the electrochemical polarization resistance methods were combined to evaluate instantaneous corrosion rates for metals and metal alloys in industrial cooling-water systems. Metal and metal−alloy samples were exposed to synthetic cooling water in a bench-scale recirculating system constructed to study corrosion under flow conditions similar to those of a cooling-water system. The measurements yielded by both methods were related through a coefficient, B′, to convert polarization resistance measurements to instantaneous corrosion rates. The metals and metal alloys tested in this study included mild steel, aluminum, copper, and cupronickel. B′ was observed to change with time initially but approach a constant value for long-term exposure (>3 days) for most metal materials. B′ values varied with metal or metal alloy studied. It was concluded that combining both methods to determine the B′ value for a metal or a metal alloy under particular exposure conditions provides a ...

Uniform corrosion, localized corrosion (pitting and crevice corrosion), cavitation, stress corrosion cracking, corrosion and mechanical fatigue, galvanic corrosion, dealloying, etc., are the common types of corrosion by which materials in desalination plants are subject to deterioration. Carbon steel, austenitic stainless steels, cupronickel alloys and titanium are prevalent materials in a modern day desalination plant. However, the majority of the failures in multistage flash (MSF) and seawater reverse osmosis (SWRO) plants have been attributed to localized attack. Localized attack in the form of pitting and/or crevice corrosion arise due to stagnation of chloride containing water, CO2 attack, presence of internal stresses, weld defect, foreign material carryover, mismatch of the material, etc. Flash chamber, pipelines, pumps, valves, heat exchanger, demister, storage tanks, intake system and power generating ancillary units may be affected by local attack. Right selection of material, skillful control o...

Minor M (M = Fe, Mn, Cr) additions are widely added to enhance the corrosion resistance of commercial cupronickel alloys. The present paper aims at optimizing the amounts of M in Cu 70 (Ni,Fe,Mn,Cr) 30 (at.%) alloys using a cluster-plus-glue-atom model for stable solid solutions. By this model, it assumed that 1 M atom and 12 Ni atoms formed an M-centered and Ni-surrounded cube-octahedron cluster and the isolated M 1 Ni 12 clusters are embedded in a Cu matrix, conforming to a cluster formula [M 1 Ni 12 ]Cu 30.3 = [M 1/13 Ni 12/13 ] 30 Cu 70 . A structure of this kind satisfies ideally the nearest neighbor requirement, i.e. only M–Ni and Ni–Cu neighbors are allowed and the unfavorable Cu–M pairs are avoided, and hence it describes a stable solid solution structure with good thermal stability. Electrochemical corrosion measurements indicated that [(Fe 0.6 Mn 0.25 Cr 0.15 ) 1 Ni 12 ]Cu 30.3 had the best corrosion resistance in 3.5% NaCl aqueous solution.

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.

The objectives of the present investigation were to characterize ammonia-producing bacteria (Bacillus sp.) and study its impact on biodeterioration of cupronickel alloy 90:10. in a nitrogen free environment. It is well known that iron sulphate and molybdenum are good inhibitors when used in a cooling water system. The interactions between inhibitor and ammonia producing bacteria on the corrosion of cupronickel 90:10 were studied. The predominated ammonia producing bacteria Bacillus sp. (AG1-EU202683; AG2-EU202684; AG3-EU202685 and AG4-EU202686) were identified by 16S rRNA gene sequencing from the biofilm. These bacteria fixed with atmospheric nitrogen for their cell protein synthesis and converted into ammonia. Ammonia enhanced pH and ammonical solution were formed in the presence of Bacillus spp. which acted as an etchant. The presence of some anodic spots in the presence of bacteria was affected by ammonia and then underwent pitting corrosion. The present study reveals that Bacillus spp. encourage intergranular attack without any stress in the cooling water system.

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.

National Natural Science Foundation of China [20406009]; Shanghai Education Committee [06ZZ67]; Shanghai Committee of Science and Technology [062312045]; Xiamen University [200512]; Key Discipline of Shanghai Education Committee of China [P1304]

This paper evaluates the effects of 550°C aging treatment on mechanical properties and corrosion resistance of Cu10Ni-3Al-1.3Fe cupronickel alloy in 0.01M Na 2 SO 4 aqueous solution. The studied material was obtained from cold rolled alloy, which was submitted to solution treatment for 1 h at 900°C, and subsequent aging treatments at 550°C for time periods up to 1,032 h. Samples were prepared from all heat treatment conditions for microstructural analysis, micro hardness measurements, tension tests and polarization tests. It is found that maximum hardness occurred after 16 h of aging. Polarization tests of heat treatment conditions show a passivity break potential (Eq), which can be related to the formation of pit-like small cavities on the polarized surfaces, which are elongated and transversal to the rolling direction. The results also show that aging process and the occurrence of precipitates does not affect the electrochemical behavior of the aged alloys, compared to the solution-treated condition.

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).

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.

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.

Cupronickels offer enhanced corrosion protection in marine environments by the formation of passive films on the surface. Cyclic voltammetric studies were carried on cupronickels in chloride solutions at pH 6.3 to understand the role of chloride ions in passive film formation. Increase in nickel content of the alloy and of chloride ions in solution decreases film resistance. Chloride ions take part in reduction of the passive film to copper. A solid-state model for passive film formation involving chloride ions has been attempted.

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