Influence of Pollution on the Corrosion of Copper Alloys in Flowing Salt Water

The morphology of horse shoe corrosion of copper and copper alloys in sea water cooled condensers in power stations is presented, and the mechanism of nucleation and of development of this type of corrosion is discussed. Horse shoe corrosion is the result of the formation of an active-passive cell: the pH of the sea water is the determining factor, and development of the corrosion is strongly influenced by the local hydrodynamic conditions. The results allow the requirements for a reliable cathodic protection of the condenser tubes to be defined.

An investigation has been made of corrosion of some binary copper alloys by high temperature water and steam under saturated pressure, 86 kg/cm2, at 300°C for 250 hours, using autoclave. Binary copper alloys containing aluminium (1, 6, 10%) silicon (1, 3, 4%), manganese (1, 5, 9%), nickel (5, 8, 15%) and tin (2, 6, 12%) were used as-rolled and annealed strip. After the corrosion test had been made, tensile tests and microscopical examination were performed and the following results were obtained. (1) Decreasing of tensile strength and elongation was remarkable on Cu-Al and Cu-Si alloys with increasing alloying element by severe intergranular corrosion. (2) Dealuminization corrosion of β′ and δ phase was observed on Cu-Al alloys of binary phase (α+β′,α+δ). (3) On the other hand, Cu-Mn, Cu-Ni and Cu-Sn alloys suffered no significant loss in tensile strength and elongation as a result of corrosion, but a little susceptibility to intergranular corrosion of Cu-Mn and Cu-Ni alloys was recognized from the microscopical examination of rolled surface of the specimens after tensile tests, due to intergranular parting. (4) Comparing corrosive action of saturated water with that of saturated steam, it was considered that the former was more corrosive that the latter.

PurposeThe corrosion of cupronickel and copper alloys in marine and chloride environments presents significant challenges in the chemical and petrochemical industries. This paper aims to investigate the corrosion inhibition of cupronickel alloy (Cu-10Ni) in a sodium chloride medium using expired amlodipine as a corrosion inhibitor. The use of this drug in its expired form could reduce the costs of corrosion and help mitigate the accumulation of pharmaceutical waste.Design/methodology/approachThe inhibitory action was evaluated using a weight loss method, potentiodynamic polarization, electrochemical impedance spectroscopy measurements, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The effect of temperature on the inhibition performance was also studied.FindingsThe results of these experiments demonstrated that the drug amlodipine effectively inhibited the corrosion of cupronickel alloy in chloride solutions. The corrosion rate of cupronickel was found to decrease with increasing inhibitor concentration and to increase with rising temperature. A maximum inhibition efficiency of 91.92 was achieved with an inhibitor concentration of 0.025 g/L at 298 K. Adsorption of the inhibitor followed the Langmuir adsorption isotherm. Polarization studies indicated that the expired drug acted as a mixed inhibitor. SEM and AFM analyses confirmed that the surface morphology of cupronickel specimens was significantly improved in the presence of the inhibitor.Practical implicationsAmlodipine can be conveniently used to mitigate problems with the corrosion of copper alloys in chloride environments.Originality/valueAmlodipine is evaluated as a novel and effective corrosion inhibitor for cupronickel alloy in neutral chloride environments.

Purpose This paper aims to investigate the modification of surface of a copper alloy by friction stir surface processing (FSSP). Design/methodology/approach The metallographic condition of the surface modification was observed using microscopy. Electrochemical corrosion tests were carried out on the modified surface and the corroded surface was observed by scanning electron microscopy (SEM). Findings The test results showed that FSSP resulted in refinement of the surface grains of the copper alloy. The degree of refinement was increased with rotation speed and increased in the descending distance of the stirring tool. The corrosion resistance of the modified surface was superior to the base metal except for the surface generated by a rotation speed of 800 rpm and a descending distance 0.1 mm. For the surface modification of the rotation speed of 800 rpm, its corrosion resistance was lower than for the other two rotation speeds. When the rotation speed is specified, the corrosion resistance is improved with increased descending distance. When the descending distance is specified, the corrosion resistance is improved with the rotation speed. Originality/value In this study, it was confirmed that the corrosion resistance of the surface modification was best at the rotation speed 1200 rpm and descending distance 0.2 mm.

The corrosion kinetics and the influence of Ce content on the corrosion performance of ZK61-xCe (x = 0, 0.5, 1.0, 1.5, wt%) magnesium alloys in NaCl (0.1 mol l−1) solution were investigated using hydrogen evolution tests combined with observations of corrosion morphology. The role of compound on the corrosion of the alloy was analyzed based on changes in the microstructure, electrode potentials of compounds and matrix, and electrochemical properties of the corrosion product film. The results show that the corrosion rate of the experimental alloy is faster in the first 3 h, then the corrosion rate is gradually reduced, and the corrosion process fits the power-exponential dynamics equation. The corrosion rate constants k and exponential n in the corrosion kinetic equations first decrease and then increase with the increase of Ce content, with the Ce content is 0.5wt%, the alloy has the slowest corrosion rate and the best corrosion resistance. The corrosion rate of the alloy is controlled by the micro-galvanic corrosion. After adding Ce to the ZK61 alloy, the MgZn2 in the alloy is converted to (Mg, Zn)12Ce with more negative electrode potential, and the electrode potential decreases from −0.811 V to −1.002 V. The electrode potential of the α-Mg matrix in the alloy is about −1.451 V, and the potential difference between the compounds and the α-Mg matrix decreases, the corrosion driving force of micro-galvanic corrosion decreases, and the corrosion resistance increases. With the increase of Ce content, the amount of (Mg, Zn)12Ce compounds increases, resulting in an increased number of micro-galvanic couples, increased migration charge density, and decreased corrosion resistance. As the corrosion proceeds, the number of (Mg, Zn)12Ce exposed on the surface of the substrate increases, blocking the contact between the substrate and the corrosion medium, himpeded lateral corrosion propagation and longitudinal corrosion extension of the α-Mg matrix.

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In this paper, a nickel anode was used for Ga electrowinning in the presence of S2- ions. The corrosion resistances of nickel and stainless steel electrodes in alkaline solutions of S2- were studied by cyclic voltammetry, XPS, and weight loss measurements. Ga electrowinning was carried out in Ga solutions with high concentrations of S2- at different current densities and NaOH concentrations. The results indicated that the nickel anode showed better corrosion resistance than the stainless steel anode. The corrosion rate of nickel was much lower than that of stainless steel due to the formation of stable passive films consisting of Ni oxide and hydroxide. The corrosion rate of the nickel anode was only 0.28 mg cm(-2) after 48 h electrowinning in the presence of 5 g L-1 S2- ions. The corrosion resistance of the nickel anode was almost independent of the NaOH concentration and the current density. When the nickel anode was used for Ga electrowinning, the current efficiency (QE) decreased in the presence of S2- owing to the reduction of the incomplete oxidation products of S2- on the cathode. The complete oxidation of S2- to SO4 (2-) was accelerated on the nickel anode, which lowered the concentrations of S2- and that of its incomplete oxidation products in solution. Bright, high-purity metallic gallium was obtained when using the nickel anode, even in Ga(III) solutions of 5 g L-1 S2-. Therefore, nickel was a suitable anode material for Ga electrowinning in Ga solutions of S2- ions.

A total of 1050 specimens of 46 different copper alloys were exposed in the Pacific Ocean at two depths, 760 and 1830 m, for periods of time varying from 123 to 1064 days in order to determine the effects of deep-ocean environments on their corrosion resistance. Most of the copper-base alloys corroded uniformly and their corrosion rates were low, 25 μm per year or less after one year at a depth of 760 m and after two years at a depth of 1830 m. A few of the alloys containing zinc, aluminum or silicon were attacked by parting corrosion. They were not susceptible to stress corrosion cracking. Only the mechanical properties of the alloys attacked by parting corrosion were adversely affected. The aggressiveness of the seawater and of the bottom sediments on the copper alloys was about the same, except for the copper-nickel alloys, where the bottom sediments were less aggressive.

: The corrosion of copper and nine wrought copper alloys is reported for exposures in five tropical environments for one, two, four, eight, and sixteen years. Weight loss, pitting, and change in tensile strength were measured to evaluate corrosion resistance. Higher corrosion rates are shown for tropical sea water immersion and tropical marine atmosphere than similar exposures in temperate climates. Of the various alloys studied, 5% Al bronze showed the highest general corrosion resistance; its 16-year losses in sea water were only 1/5 that of copper. Copper and the high-copper alloys were resistant to all environments and generally had decreasing corrosion rates with time of exposure. Tensile tests revealed heavy dezincification in the lower-copper brasses when exposed in marine environments, and for two of the brasses in fresh water immersion. As a result of the decreasing corrosion rates or dezincification, antifouling properties of copper alloys decreased with time of exposure. All were moderately to heavily fouled after 16 years in sea water. Galvanic effects were pronounced in tropical sea water. The corrosion of copper alloys was accelerated appreciably by contact with stainless steel (316) of 1/7 their area, while similar carbon steel strips gave effective cathodic protection of plates of brass and bronze over the long term.

PurposeThis paper aims to study the corrosion behaviour of copper alloys HSn70‐1 + As and B30 in water with sulphide.Design/methodology/approachThe mass‐loss method, electrochemical tests and surface analysis were used to study the corrosion behaviour of copper alloys HSn70‐1 + As and B30 in water with sulphide.FindingsDezincification corrosion occurred on HSn70‐1 + As both in water with or without sulphide, and sulphide in water accelerated corrosion, while for the copper alloy B30, the corrosion rates were very small both in water with or without sulphide, although corrosion was also accelerated by sulphide in water.Practical implicationsIn order to prevent copper alloys HSn70‐1 + As and B30 in water with sulphide from corroding, S2− must be removed.Originality/valueIt was found that sulphide in water accelerated the corrosion of copper alloys HSn70‐1 + As and B30 in this paper. Therefore, when water containing sulphide is used as the source of make‐up water and cooling water, S2− in water must be removed to prevent the pipelines and facilities from corroding. This means that the research results can offer theoretical guidelines for the prevention of pipelines and facilities in the power plant from corroding.

The most cause of troubls of aluminium brass widely used for heat exchanger tubes in petroleum refining plant lies in its high susceptibility to stress corrosion cracking. Stress corrosion of Cu-Zn alloy has been investigated extensively, while little study has been made on that of Cu-Zn-Al alloy. Authors have studied the stress corrosion of Cu-Zn-Al ternary alloys and effects of additional element to the stress corrosion.(1) Addition of silicon to aluminium brass remarkably lowers the alloy's susceptibility of the alloy to stress corrosion.(2) Aluminium brass containing silicon does not greatly depart from plain aluminium brass in corrosion resistance to sea water and sulfide, and also in mechanical and physical properties.(3) From the above-mentioned facts, it appears that, for heat exchanger tubes in petroleum refining plant, aluminium brass modified with silicon exceeds the customary aluminium brass in inhibiting stress corrosion failure. Besides, it does not seem to cause any other troubles in its use.(4) Mechanism on how the addition of silicon affects the stress corrosion susceptibility has been studied. And it has been found that the mechanism is principally attributed to some chemical factors.

The effectiveness of synthesized antipyrinyl‐imidazotriazole and its derivatives as inhibitors for the corrosion of copper alloy in 0.5 M H2SO4 solution was tested using weight loss, electrochemical impedance spectroscopy (EIS) and potentiodyanmic polarization techniques. The generated results confirmed that the tested compounds have strong inhibition efficiencies for the protection of the corrosion of copper alloy in 0.5 M H2SO4. Maximum inhibition efficiencies (IEs) evaluated from electrochemical measurements at inhibitor's concentrations of 0.040 g/L were 85% (5‐(4‐Antipyrinyl)‐3H‐imidazo[1,2‐b][1,2,4]triazole), 60% (6‐Antipyrinyl‐imidazo[2,1‐b]thiazole) and 72% (2‐Antipyrinyl‐7‐ethoxy‐imidazo[2,1‐b]benzothiazole). It was observed that the inhibition efficiency was strongly influenced by the flow rate of the solution and was reduced to 79 (5‐(4‐Antipyrinyl)‐3H‐imidazo[1,2‐b][1,2,4]triazole), 60% (6‐Antipyrinyl‐imidazo[2,1‐b]thiazole), and 44% (2‐Antipyrinyl‐7‐ethoxy‐imidazo[2,1‐b]benzothiazole) at an agitation speed of 400 rpm. EI from weight loss was comparable with those from PDP of mixed‐type inhibition style and EIS of diffusion model. The low inhibition efficiency for 6‐Antipyrinyl‐imidazo[2,1‐b]thiazole was significantly enhanced from 60% to 90% through a synergistic effect of 0.0001 M KI. The Temkin and Frumkin isotherms indicate the physical adsorption of inhibitors on copper surface. Condensed Fukui function calculations reveal a common center for electrophilic attacks in the three molecules: the nitrogen in the bridged pyrrole rings (labeled as N11).

An investigation of anodic film formation on electrodeposited ruthenium by potential sweep techniques

ABSTRACTMultilayered Ir oxide films were prepared on Ti and Pt:Ir electrodes by the thermal decomposition of successive layers of alcohol solutions of IrCl3. The charge capacity of the thermally-formed Ir oxide films (TIROF) and the reversibility of surface oxide-related reactions were evaluated in a physiological saline solution using potential sweep and current pulse techniques. The TIROF-coated electrodes had electrochemical properties similar to an Ir electrode coated with an anodically-formed oxide. The charge injection limits before gassing ranged from 5–10 mC/cm2 for TIROF-Ti and 1–3 mC/cm2 for TIROF-Pt:Ir with biphasic, charge-balanced current pulses of 0.2 ms duration. No Pt dissolution was detected during >100 hr stimulation with TIROF-Pt:Ir electrodes. Small amounts of Ir dissolution were detected which might result from passive leaching of residual chloride complexes of Ir. The TIROF coatings remained firmly attached to the substrate metal during long term pulsing and abrasion tests. The properties of TIROF coatings, e.g., high charge capacity for reversible charge injection and good abrasion and corrosion resistance, are of great advantage for neural prosthesis applications.

Selective oxide growth at a rhodium-platinum alloy under potential cycling conditions in base