On size effect of rate of corrosion of copper nanowire ensemble: Part 2. Size effect of rate of corrosion of copper in pyrophosphate solution

The corrosion of specimens of copper produced by electroplating on disc electrodes 10–500 μm in diameter from a pyrophosphate electrolyte is studied in this electrolyte (without added copper ions) using polarization curve measurements. It is found that the rate of corrosion of the microelectrodes with a radius of 5 μm is eight times higher than that of the microelectrodes with a radius of 25 μm; the measured rate of corrosion remains unchanged when varying the radius of the microelectrode in a range of 25–250 μm. It is shown that the process under investigation is corrosion with oxygen depolarization; the rate of reduction (of dissolved oxygen) increases eightfold when varying the radius of the microelectrode in a range of 5–25 μm. The experimental results are confirmed by the calculations of diffusion currents for the microelectrodes, which show that the size effect, i.e., an increase in the diffusion current density with decreasing area of the electrode surface, should be observed for electrodes with a radius less than 20–30 μm.     

Comparison of the corrosion properties of bulk copper samples and an electrodeposited copper nanowire array in a pyrophosphate electrolyte

Using different electrochemical methods (open circuit potential (OCP) measurements, polarization studies, and electrochemical impedance spectroscopy), it has been shown that the corrosion of copper in a pyrophosphate solution occurs with oxygen depolarization. The electrochemical impedance spectroscopic measurement of the corrosion resistance of an array of nanowires of copper electrodeposited into the pores of an Al₂O₃ template has revealed that the corrosion resistance is significantly affected by the pore diameter of the template.     

The effect of adatoms on the corrosion rate of copper

On the premises that corrosion is a surface process and adatoms modify the electronic states of the surface, the influence of Zn, Sn, S, I, F, Ta, Sb, Ti, Bi and Cr adatoms on the corrosion rate of copper was investigated. Adatoms were adsorbed at open-circuit from a solution containing 1.0×10⁻² mol l⁻¹ of the ions of the adatom element. The coverage of the adatoms at the surface was calculated by integration of the area under one of the peaks on the voltammogram of the copper electrode before and after dosing the electrode with the adatom. A significant difference in adsorbability of the adatoms at copper surface was observed. This difference was inter alia attributed to atomic size, crystallographic and kinetic effects. The surface properties were characterized by cyclic voltammetry, and for selected systems by SEM and electron microprobe. Corrosion of the surface in presence and in absence of the adatoms was followed by weight-loss method while surface oxidation, ‘surface corrosion’ was investigated by cyclic voltammetry and by electrochemical polarization techniques. The results showed that the nonmetals (F, S and I) markedly enhanced the rate of corrosion; Cr, Ta, Sb, Bi, Ti, Sn slightly enhanced the rate of corrosion of copper. Zinc, however, was the only element which decreased the rate of corrosion.     

AC corrosion. Part 2: Parameters influencing corrosion rate

Pipelines and AC power transmission lines frequently share corridors leading to AC interference corrosion problems, as documented by pipeline failures that have occurred in the USA, Canada and Europe, even when cathodic protection is applied. In order to investigate these phenomena, weight loss tests on carbon steel samples were performed in soil-simulating conditions (aerated and de-aerated sulphate solutions) at various AC current densities from 10 to about 900 A/m². Tests on freely corroding samples showed that the corrosion rate increased as AC current density increased; the effect of AC on corrosion rate was also detected at current densities lower than 30 A/m². The results obtained are analyzed and discussed together with polarization test results, which were presented in a previous paper by Goidanich et al. (submitted for publication) [1].     

The effect of post-treatment of a high-velocity oxy-fuel Ni-Cr-Mo-Si-B coating Part I: Microstructure/corrosion behavior relationships

The microstructure and aqueous corrosion characteristics of a Ni-Cr-Mo-Si-B high-velocity oxy-fuel (HVOF) coating have been assessed. It has been shown that postprocessing by vacuum fusion has a significant effect on the coating microstructure by increasing the type and concentration of hard phase particles. The principal hard phases in the as-sprayed condition and vacuum-sealed condition are chromium carbides, whereas molybdenum-containing boride phases are also present after vacuum fusion. Vacuumfusion post-treatment eliminates splat boundaries, which can act as sites, where preferential corrosion can occur and, hence, the dominant corrosion mechanisms change. In as-sprayed and vacuum-sealed coatings, localized attack at splat particle boundaries and crevice corrosion dominate, whereas in vacuum-fused coating, the principal mechanism of corrosion is “micropitting” as a result of the hard phase loss.     

The a.c.-induced corrosion of copper neutrals

Electrochemical behaviour of tin-coated copper electrodes in a model soil environment was studied by means of electrochemical impedance spectroscopy (EIS), d.c. polarization, and long-term exposure testing. Comparison of EIS spectra, modelled as a simple R(RC) circuit, taken over a period of time at rest potential, with those taken under anodic and cathodic bias potentials, shows an increase in the electron transfer resistance under conditions of anodic bias or a.c. polarization. This indicates that the tin coating is passivated by the a.c. signal through oxide formation during the anodic half cycle. This observation is supported by rest potential measurements. Without an a.c. signal the potential of tin-coated wire stabilizes at a more negative potential than that of bare copper wire and provides cathodic protection to copper exposed through coating flaws. However, when an a.c. signal is added, the potential of the tincoated wire shifts to a more positive potential than that of the bare wire, passivating the tin coating and rendering it cathodic to the underlying copper. The large area of the tin cathode relative to the small area of exposed copper substrate leads to rapid pit initiation in the copper, resulting in premature failure of the cable in the soil environment.     

Micromechanical study of corrosion products layers. Part I: Experimental characterization

A micromechanical characterization had been performed on ancient artefacts corrosion products. The proposed experimental approach allies scanning electron microscopy observations, micro-indentation tests which allow the characterization of the local stiffness of elementary constituents, and finally Raman micro-spectroscopy tests which give access to the local crystallised phases of the samples. The experimental campaign contains a large series of tests, which give us the opportunity to interpret the dispersion of local stiffness measurements.     

Effects of alternating magnetic field on the corrosion rate and corrosion products of copper

The effects of alternating magnetic field on the corrosion morphologies, corrosion rate, and corrosion products of copper in 3.5% NaCl solution, sea water, and magnetized sea water were investigated using electrochemical test, scanning electron microscopy/energy dispersive analysis system of X-ray (SEM/EDAX), and X-ray diffraction (XRD). The results show that the corrosion rate of copper in magnetized sea water is minimal. Moreover, the surface of the specimen in magnetized sea water is uniform and compact as compared with those in 3.5% NaCl solution and sea water. The corrosion products of copper in magnetized sea water are mainly Cu2O and CuCl2. However, the corrosion products in sea water are CuCl, Cu2Cl(OH)3, and FeCl3·6H2O. The electrochemical corrosion mechanisms of copper in the three media were also discussed.     

Contact corrosion of metals in aqueous media. Part I

The corrosion behavior of aluminum, steel, and cast iron in aqueous solutions is studied both for individual metal specimens and short-circuited systems (aluminum-steel, aluminum-cast iron, steel-cast iron, and aluminum-steel-cast iron). It is shown that aluminum behaves as a cathode with respect to steel and cast iron. The high corrosion rates of ferrous metals are caused by the specificity of iron surface state in aqueous solutions of electrolytes. Original Russian Text ? V.N. Esenin, L.I. Denisovich, 2007, published in Zashchita Metallov, 2007, Vol. 43, No. 4, pp. 390–395.     

The effect of purine on the corrosion of copper in chloride solutions

The influence of the concentration of purine (PU) on the corrosion and spontaneous dissolution of copper in 1.0 M NaCl solutions (pH 6.8) was studied. The investigations involved electrochemical polarization methods as well as weight-loss measurements, electrochemical quartz crystal microbalance (EQCM) techniques and scanning electron microscopy (SEM). The inhibition efficiency (IE) increases with an increase in the concentration of PU. An adherent layer of inhibitor is postulated to account for the protective effect. The adsorption of PU has been found to occur on the surface of copper according to the Langmuir isotherm. Purine is chemically adsorbed on the copper surface.     

Organic acid vapours and their effect on corrosion of copper: a review

Abstract

Carboxylic acids of low molecular weight, such as formic, acetic, propionic and butyric acids, as well as other acids (n-pentanoic, hexanoic, heptanoic, etc.), are present in rain, snow, clouds and particulate matter. They contribute about 16–36% of rain acidity. It is estimated that ～64% of formic acid and ～88% of acetic acid are in the vapour phase. Carboxylic acids are produced by the combustion of biomass, and analyses of the smoke from fire events reveal concentrations of about 300–500 ppb for formic acid and 3000–5000 ppb for acetic acid. Industrial emissions of carboxylic acid are produced by plants processing biological materials, such as food, paper, wood, etc. Acetic acid vapours are found in several industrial atmospheres. Vinegar is one important source of acetic acid vapours in food processing plants. The present review shows that for copper specimens exposed to organic vapours for 21 days at 100% relative humidity (RH) and a contaminant level in the range of 10–300 ppm, the relative aggressiveness of these acids is (from high to low): acetic>formic>butyric>propionic.     

The effect of corrosion inhibitors in drinking water installations of copper

To test the effect of corrosion inhibitors in drinking water installations of copper, 13 test pipe rigs (copper tubes and ring coupons) were exposed to a supply water of a water company in Northrhine‐Westphalia for a test period of one year. The testing conditions were similar to those in a real domestic installation with respect to stagnant and flow conditions. Phosphate (PO₄), silicate (SiO₂) and combinations of phosphate/silicate have been used in different concentrations ranging from 2.2–4 mg/L PO₄ and 3–12 mg/L SiO₂. The results have shown that all tested inhibitors were able to reduce copper concentration and corrosion rates, but the specific efficiency of pure phosphate was greater than of pure silicate. The results have also shown that there are eminent differences in the mechanism. The dosage of phosphate‐based inhibitors (pure phosphate, phosphate/silicate) guides to a chemical stabilisation of the copper surface layer by building poorly soluble compounds of copper‐ions and phosphates and so they interfere in the reaction kinetics of the dissolution of the copper surface layer. Adding pure silicates, thin films are built which act as a chemical stabilisation of the external area of the copper layer; but the subsurface layer is not influenced in structure and chemical composition.     

The effect of temperature on the corrosion of steel in concrete. Part 2: Model verification and parametric study

A comprehensive model for predicting the corrosion rate of steel in concrete has been developed using the concept of simulated polarization resistance experiments. This model is developed by carrying out a nonlinear regression analysis on data obtained from numerical experiments that are based on the solution of Laplace’s equation in a domain determined by the polarized length of the rebar. This part of the paper provides a comprehensive verification of the developed model and illustrates the application of the model to investigate the coupled effects of parameters affecting corrosion of steel in concrete. The results of the verification study show that the model predictions are in good agreement with the experimental data.     

Wear‐corrosion of nitrided steel: corrosion potential monitoring to evaluate the effect of test parameters

Corrosion and wear are the most destructive processes for a material surface and the combination of these two phenomena causes severe problems in several engineering applications. In order to characterize wear‐corrosion resistance in the most appropriate way it is necessary to measure the degradation parameters (weight loss, corrosion rate) during wear testing carried out in an aggressive environment. As a first approach to study the wear‐corrosion phenomenon the corrosion potential (E_corr) was used as a diagnostic of the behaviour of the tested material. In this paper the behaviour of a nitrided steel was evaluated. In this study the effects of some working parameters such as rotation speed, applied load and electrolyte type on such electrochemical parameter were analysed. It was shown that E_corr values are noticeably affected by variations in testing conditions because of both fluodynamical changes and wear mechanisms. During wear‐corrosion tests, the application of a load allows a remarkable decrease in E_corr which becomes more evident as the load or the rotation speed increase. When the mechanical action is not so severe (low load and low rotation speed) a partial metal “repassivation” can be observed because of the metal interaction with the electrolyte. However potential measurements only allows us to observe qualitative changes in the system. A quantitative evaluation needs to measure the total weight loss and corrosion rate with and without wear.     

Seasonal variations in corrosion rate and runoff rate of copper roofs in an urban and a rural atmospheric environment

This paper summarizes the results from an extensive field exposure program implemented to study possible seasonal dependencies of copper corrosion rates and runoff rates. Two-year exposures in one urban and one rural environment were performed at four different starting seasons. An extensive multi-analytical approach was undertaken of all exposed samples.Seasonal differences in corrosion product formation was observed during the first month of exposure and attributed mainly to differences in relative humidity conditions. Seasonal differences in corrosion rate at the rural site could be discerned throughout the whole two-year exposure, again, mainly attributed to differences in relative humidity. No seasonal effect could be observed at the urban site indicating that other parameters influenced the corrosion kinetics at this site. While corrosion rates exhibit a continuous decrease with exposure time, the yearly runoff rates are independent of time. Depending on starting months the yearly copper runoff rates ranged from 1.1 to 1.7 g m⁻² y⁻¹ for the urban site, and from 0.6 to 1.0 g m⁻² y⁻¹ for the rural site. These seasonal variations were primarily attributed to differences in precipitation quantity and environmental characteristics. Runoff rates are significantly lower than corrosion rates as long as the adhering copper patina is growing with exposure time.A full risk assessment requires not only information on the total amount of copper in the runoff, but also on its chemical speciation. Under present conditions, 70–90% of all copper in runoff water collected immediately after leaving the surface is present as the most bioavailable form, the hydrated cupric ion, Cu(H₂O)₆²⁺.     

Effect of atmospheric pollutants on the corrosion of high power electrical conductors - Part 2. Pure copper

The research work performed during this study was simultaneously followed with another one published in this journal as Part I. A1 and 6201 A1 alloy. Its aim was to reveal a comparative picture of the joint effect of marine and industrial atmospheric pollutants on the corrosion resistance of wire metals employed for electric transmission conductors. Weight loss after 4, 11, 16 and 24 months exposure was determined and morphology of the attack analysed through SEM-ESEM-EDX. Cu corrosion products showed higher protectiveness than those of Al in marine sites for the lowest [Cl⁻] and in marine-industrial atmospheres even for the highest SO₂ contents. Respect to marine sites where [Cl⁻] was higher than [SO₂] Cu was more susceptible than A1.     

The effect of grain size on the corrosion behaviour of inconel 600 in high-temperature steam

The effect of grain size on the corrosion behaviour of Inconel 600 has been studied in steam of 40 atm pressure at 800°C. A protective Cr₂O₃-rich scale is formed initially. After this introductory stage, nodular oxides nucleate at the positions where cracks have occurred in the Cr₂O₃-rich scale. The weight gain due to steam corrosion has a tendency to decrease with increasing grain size in the stage where the Cr₂O₃-rich scale is formed. This tendency is reversed in the nodular oxide-forming stage, where the weight gain increases with increasing grain size. The effect of grain size on the corrosion behaviour in the two stages is discussed.     

Predicting the chemistry,corrosion potential and corrosion rate in a crevice formed between substrate steel and a disbonded permeable coating with a mouth

A model developed in an earlier work was used in this work to investigate the effect of coating permeability on the evolution of solution chemistry, corrosion potential, and rate in a crevice formed between a steel surface and a coating disbonded from it. The crevice gap varies along distance from the mouth, and the coating is permeable to ions and/or oxygen (O₂). The earlier work focused specifically on modeling the effect of variable gap (on crevice corrosion) with the coating impermeable to either ions or O₂. In both works, the crevice chemistry was an aerated, diluted sodium chloride solution, which at the mouth was set to be different from that initially in the crevice. The results of this work show that a permeable coating behaves like a membrane, which, under a cathodic polarization at the crevice mouth, tends to raise the in-crevice sodium ion concentration and pH more rapidly relative to an impermeable coating. Later, as the sodium ion concentration and pH in the crevice become greater than at the mouth, the permeable coating tends to reverse the transport direction for ions. At a mouth potential of ?0.900 V vs. saturated Cu/CuSO₄, the cathodic current is sufficient to suppress all O₂ penetrating the crevice both from the mouth and through the coating. The practical implication is that in the presence of sufficient cathodic polarization, a permeable coating, when disbonded, can still be capable of protecting the substrate steel from corrosion attack.     

The phototarnishing of silver and copper. Part II

Tarnishing of silver and copper at room temperatures in the presence of CH₃I, HI, CH₃Br, and HBr is caused by absorption of ultraviolet light of appropriate frequency by the growing metal halide scale. No appreciable thermal tarnishing of silver or copper is observed in the presence of these gases at room temperature. The kinetics of the phototarnishing reactions are linear and the rate depends linearly on the incident light intensity. It is concluded that the primary photochemical process is the production in the metal halides of free electrons which then react with adsorbed gas molecules, thereby propagating the reaction.For Part I, see P. T. McTigue and D. J. Young,Aust. J. Chem. 18, 1851 (1965).     

The effect of temperature on the corrosion of steel in concrete. Part 1: Simulated polarization resistance tests and model development

The effect of temperature on the corrosion rate of steel corrosion in concrete is investigated through simulated polarization resistance experiments. The simulated experiments are based on the numerical solution of the Laplace’s equation with predefined boundary conditions of the problem and have been designed to establish independent correlations among corrosion rate, temperature, kinetic parameters, concrete resistivity and limiting current density for a wide range of possible anode/cathode (A/C) distributions on the reinforcement. The results, which successfully capture the resistance and diffusion control mechanisms of corrosion as well as the effect of temperature on the kinetic parameters and concrete/pore solution properties, have been used to develop a closed-form regression model for the prediction of the corrosion rate of steel in concrete.