Corrosion of copper in seawater and its aerosols in a tropical island

A complete characterization of copper corrosion behavior has been carried out under permanent immersion, water line, splash zone and at the atmosphere (near and far from the sea) at the tropical Cuban archipelago. No significant differences have been determined for corrosion of copper under complete immersion for test sites representative of Cuban archipelago. The maximum corrosion rate was observed on the line of water, related to the partial removing of the corrosion products layer due to water movement (waves) and a higher availability of oxygen. Patina composition was characterized using XRD, IR, EDS and SEM techniques. Paratacamite (Cu₂(OH)₃Cl) was the main component of the patina formed under complete immersion, on the line of water and in the splash zone. In poorly polluted atmospheric marine environments also atacamite (another structural modification of Cu₂(OH)₃Cl) was found. When environmental SO₂ reaches a competitive level with the chloride aerosol the patina formed is a complex mixture of basic cupric chlorides (paratacamite and atacamite) and basic cupric sulfates, antlerite (Cu₃(SO₄)(OH)₄) and brochantite (Cu₄(SO₄)(OH)₆). Brochantite and basic cupric chlorides are detected at inland rural sites. The patina morphology reveals details about the local environment in which it is formed and shed light on its more or less protective role for the metal. The relatively large corrosion rate under complete immersion and on the line of water is related to the formation of a patina with poor adherence to the metal surface and to a porous layer of cuprite formed by relatively large octahedral crystals.     

Effects of blending on surface characteristics of copper corrosion products in drinking water distribution systems

Copper scales formed over 6-months during exposure to ground, surface and saline waters were characterized by EDS, XRD and XPS. Scale color and hardness were light red-brown-black/hard for high alkalinity and blue-green/soft for high SO₄ or Cl waters. Cl was present in surface or saline copper scales. The Cu/Cu₂O ratio decreased with time indicating an e transfer copper corrosion mechanism. Cu₂O, CuO, and Cu(OH)₂ dominated the top 0.5-1 A° scale indicating continuous corrosion. Cu₂O oxidation to CuO increased with alkalinity, and depended on time and pH. Total copper release was predicted using a Cu(OH)₂ model.     

Examination of Aluminum Corrosion Products in Marine or Industrial Marine Atmosphere

A method has been developed to characterize the passivation film formed on aluminum in marine atmosphere, whether polluted or not by sulphur oxides and fluorides The information thus obtained was integrated by X-ray diffractometric analyses. The following corrosion products were found in the marine atmosphere: Al₂O₃· 3H₂O + Al (oxychoride) + Al (hydroxide) (The latter two compounds had not been revealed by X-ray analysis). The corrosion products found in the polluted atmosphere were: AlF₃; Al₂(SO₄)₃ · H₂SO₄; Al₁₁(OH)₃₀Cl₃; AlF_1.96(OH)_1.4; 16Al(OH,F)₃ · 6H₂O; AlF_1.65(OH)_1.35 · H₂O. Since the developed method provides useful quantitative information on the aluminum distribution between the various anions, it is deemed to be a useful tool to study the corrosion kineties and mechanism.     

Characterization of Atmospheric Corrosion of 2A12 Aluminum Alloy in Tropical Marine Environment

In this work, corrosion product formed on 2A12 aluminum (Al) alloy after 3 months of natural exposure in South China Sea atmosphere was characterized by various surface analysis techniques, including scanning electron microscopy, energy-dispersive x-ray analysis, x-ray photoelectron spectroscopy, and x-ray diffraction. The atmospheric corrosion mechanism of Al alloy in marine environment was derived. Results demonstrated that Al alloy specimen experiences serious general corrosion and pitting corrosion. Al and O are enriched in the product film, and Ca and Cl are also found in the film and corrosion pits in Al alloy substrate. The main component compounds existing in the film include Al₂O₃, Al(OH)₃, and AlOOH while AlCl₃ and CaCO₃ are also identified. Al alloy encounters corrosion under tropical marine atmosphere. Although somewhat protective, the formed surface film on Al alloy specimen is attacked by chloride ions, resulting in significant pitting corrosion of Al alloy.     

Effect of alloying elements on the electrochemical polarization behavior and passive film of Fe-Mn base alloys in various aqueous solutions

The corrosion properties of austenitic Fe-Mn, Fe-Mn-Al, Fe-Mn-Cr and Fe-Mn-Al-Cr alloys with compositions of 23-30 wt% Mn, 2.8-8.2 wt% Al and 4.9-6.9 wt% Cr in various aqueous solutions of pH −0.8 to 15.3 and the passivating mechanism induced by the presence of Al, Cr, or Al and Cr have been studied using electrochemical measurements and Auger electron spectroscopic/X-ray photoelectron spectroscopic analysis. Binary Fe-Mn alloys can be passivated only in 10-50% NaOH solutions, and alloying of binary Fe-Mn alloy with Al or Cr or combination of Al and Cr seems not so obviously beneficial to corrosion resistance in HNO₃ or Na₂SO₄ solutions. All of the experimental Fe-Mn based alloys and steels for comparison cannot passivate in either 10% HCl or 3.5% NaCl solution. The Fe-Mn based alloys containing Al or Cr or Al and Cr can passivate in 10-50% HNO₃ or 1 mol l⁻¹ Na₂SO₄ solutions and rainwater. In general, Fe-Mn based alloys can passivate in oxidizing acid, neutral and basic solution, but cannot passivate in reducing acid or solution containing active Cl⁻ ions. In the passive film formed on the surface of Fe-Mn base alloys in various aqueous solutions, bound water and hydroxides are present at the surface of the film, while mixed oxides of Al, Cr, Mn and Fe are located in the inner part. The resistance to corrosion is imparted by a barrier film of bound water, hydroxides and oxides of Al, Cr or Fe, while the Mn oxides in passive film reduce the corrosion resistance.     

Corrosion Behavior of Cu40Zn in Sulfide-Polluted 3.5% NaCl Solution

The corrosion behavior of a duplex-phase brass Cu40Zn in clean and sulfide-polluted 3.5% NaCl solutions was investigated by conducting electrochemical and gravimetric measurements. The corrosion product films were analyzed by scanning electron microscopy, energy-dispersive spectroscopy and x-ray diffraction. The presence of sulfide shifted the corrosion potential of Cu40Zn toward a more negative value by 100 mV and increased the mass loss rate by a factor of 1.257 compared with the result in the clean solution. The corrosion product film in the clean solution was thin and compact; it mainly consisted of oxides, such as ZnO and Cu₂O. By contrast, the film in the sulfide-polluted solution was thick and porous. It mainly contained sulfides and zinc hydroxide chloride (i.e., Zn₅(OH)₈Cl₂·H₂O). The presence of sulfide ions accelerated the corrosion damage of Cu40Zn by hindering the formation of protective oxides and promoting the formation of a defective film which consisted of sulfides and hydroxide chlorides.     

X-ray diffraction phase analysis of crystalline copper corrosion products after treatment in different chloride solutions

The corrosion products Cu₂(OH)₃Cl, Cu₂O, and CuCl₂ were identified on the surface of copper plates after their four days treating in three different sodium chloride, sodium/magnesium, and sodium/calcium chloride solutions using X-ray diffraction powder analysis. However, the quantitative proportions of individual corrosion products differ and depend on the type of chloride solution used. Treating of copper plates only in the sodium chloride solution produced the mixture of corrosion products where Cu₂O is prevailing over the Cu₂(OH)₃Cl and CuCl₂ was not identified. The sample developed after treating of the cooper surface in the sodium/magnesium chloride solution contains Cu₂(OH)₃Cl and CuCl₂ prevailing over the Cu₂O, while the sample developed after treatment of copper in sodium/calcium chloride solution contains Cu₂(OH)₃Cl prevailing over CuCl₂ and Cu₂O was not identified.     

Influence of the corrosion products of copper on its atmospheric corrosion kinetics in tropical climate

In the present paper, the identification of the corrosion product phases formed on copper under different atmospheres of Cuban tropical climate is reported. Cuprite (Cu₂O), paratacamite (Cu₂Cl(OH)₃), posnjakite (Cu₄SO₄(OH)₆ · 2H₂O) and brochantite (Cu₄SO₄(OH)₆) were the main phases identified by X-ray diffraction (XRD) analysis and Fourier transform infrared spectroscopy (FTIR).Copper corrosion products are known to have a protective effect against corrosion. However, a different behaviour was obtained under sheltered coastal conditions. This can be due to the corrosion products morphology and degree of crystallisation, rather than their phase composition. A higher time of wetness and the accumulation of pollutants not washed away from the metal surface can also play an important role.     

Electrochemical simulation of vapour side corrosion of Cu–Ni condenser tubes in multistage flash evaporation distillers

Abstract

The corrosion of 70–30 Cu–Ni condenser tubes in the vapour of multistage flash evaporation distillers occurs within a thin water film adhering to the metal surface. This, together with the fact that corrosion involves the alternate formation and dissolution of copper oxides, justifies the application of electrochemical techniques in aqueous solutions for the study of vapour side corrosion. Open circuit potential (OCP) transients were used to establish the effects of vacuum and of O₂ , CO₂ , and mixtures thereof on the corrosion process. The study was carried out in 4%Na₂ SO₄ solution at ambient temperatures. The state of vacuum in the distiller was simulated by purging the solution with N₂ gas. The OCP of the working electrode tended towards more negative values, revealing the instability of the air formed oxide. This changed slowly to a Cu₂O film. Introduction of O₂ into the cell resulted in the instantaneous shift of potential towards less negative values. Cuprous oxide was oxidised to hydrated cupric oxide. Reintroduction of N₂ gave rise to a clear potential step related to the slow decomposition of Cu(OH)₂ to fresh Cu₂O. The latter oxide thickened with time. Flushing of the solution with CO₂ , following deaeration, also caused the OCP to change to more positive values. The change was, however, a result of the solution turning acid, causing slow attack on Cu₂O. This was gleaned from the results of N₂ purging, in which a gradual, linear decrease of potential to the Cu₂O value occurred. A 1 : 1 mixture of O₂ and CO₂ caused the OCP of the electrode to move in the positive direction. Both Cu₂O and Cu(OH)₂ dissolved in the acid solution. Introduction of N₂ caused the OCP to shift to the Cu/Cu₂O potential. This stage was, however, short lived and the potential moved once more towards less negative values. This behaviour is attributed to the occurrence of the autocatalytic reaction Cu²⁺ + Cu = 2Cu+. The conclusion finds support in the results of a second cycle, in which the potential fluctuated between those of oxide formation and metal dissolution. Comparison is made between the results of corrosion in aqueous solutions and in the vapour phase. Open circuit potential measurements in solution confirmed and extended the results of weight loss determinations in the vapour phase.     

The corrosion and passivity of aluminum exposed to dilute sodium sulfate solutions

The composition and thickness of the oxide/hydroxide film that forms on pure aluminum surfaces that are polarized in 0.05 M Na₂SO₄ in acidic, near-neutral, and alkaline solutions have been characterized using XPS. The results of this effort have been plotted on surface behavior diagrams to follow the evolution of the surface film during polarization. Although a thin layer of gibbsite [Al(OH)₃] is often indicated to be the film that forms and protects aluminum from corroding in near-neutral pH solutions after 10–20 h of exposure, the composition of the film that initially forms on Al after a short period of time (1 h) was actually closer to boehmite (AlOOH), the oxyhydroxide phase. This film generally grows thicker during either anodic or cathodic polarization in both the pH 7 and pH 10 solutions. For the solution at pH 2, the air-formed film dissolves to a very thin oxyhydroxide film that is replaced by an oxide film, Al₂O₃, during anodic polarization. The growth of the oxyhydroxide film at each pH during cathodic polarization is attributed to the local buildup of hydroxyl ions at the surface of the working electrode.     

Surface characterization and corrosion behavior of a novel gold-imitation copper alloy with high tarnish resistance in salt spray environment

A novel gold-imitation copper alloy (CuZnAlNiSnBRe) was designed and its corrosion behavior in salt spray environment was investigated. The new alloy has better tarnish resistance and corrosion resistance than the current coinage alloy used in China (H7211). A multi-layer film formed on the surface of the new alloy after a period of exposure to salt spray was responsible for the good resistance of the alloy. The corrosion products were a mixture of CuO, Cu₂O, ZnO, Al₂O₃ and Al(OH)₃, with the transition from Cu₂O to CuO occurring during the corrosion process.     

The effect of pH,copper content and ammonia concentration on the stress corrosion cracking susceptibility of an aged Cu−4%Ti alloy

Stress corrosion cracking tests of an aged Cu?4% Ti alloy in various copper-ammonia solutions revealed that the alloy was highly susceptible to stress corrosion cracking in highly alkaline solutions with preconcentrated copper, but almost immune in Mattsson solutions (pH 3.9–10.0). The surface film (Cu₂O) may be not an important factor in stress corrosion cracking in this alloy system. Increase in preconcentrated copper content and ammonia concentration leads to a decrease in the time to failure. Preconcentrated copper enhances the stress corrosion susceptibility by promoting preferential dissolution of copper through acceleration of the cathodic reaction. In the highly susceptible solutions, the corrosion process seems to be mainly controlled by diffusion of cupric complex ions and the preferential corrosion of copper under concentration polarization.     

Corrosion Resistance of Copper Coatings Deposited by Cold Spraying

In the article, a study of corrosion resistance of copper and copper-based cermet (Cu+Al₂O₃ and Cu+SiC) coatings deposited onto aluminum alloy substrate using the low-pressure cold spraying method is presented. The samples were subjected to two different corrosion tests at room temperature: (1) Kesternich test and (2) a cyclic salt spray test. The selected tests were allowed to simulate service conditions typical for urban, industrial and marine environment. Examination of corroded samples included analysis changes on the coating surface and in the microstructure. The physicochemical tests were carried out using x-ray diffraction to define corrosion products. Moreover, microhardness and electrical conductivity measurements were conducted to estimate mechanical and physical properties of the coatings after corrosion tests. XRD analysis clearly showed that regardless of corrosion conditions, for all samples cuprite (Cu₂O) was the main product. However, in the case of Cu+Al₂O₃ cermet coating, chlorine- and sulfate-containing phases such as Cu₂Cl(OH)₃ (paracetamite) and Cu₃(SO₄)(OH)₄ (antlerite) were also recorded. This observation gives better understanding of the lowest microstructure changes observed for Cu+Al₂O₃ coating after the corrosion tests. This is also a justification for the lowest decrease in electrical conductivity registered after the corrosion tests for this coating.     

稀硫酸溶液清洗电镀铜晶种(英文)

采用稀硫酸溶液清洗以除去在铜晶种表面形成的氧化物。将通过溅射沉积在Ti/Si(100)薄片上生成的铜晶种暴露在空气中来生长原生铜氧化物。用稀硫酸溶液和TS-40A碱性清洗剂除去原生铜氧化物。先用TS-40A碱性清洗剂预处理以除去铜晶种表面的有机物,再用稀硫酸溶液除去铜氧化物(Cu2O和CuO)以及有机物和Cu(OH)2。     

Effect of aluminum on the corrosion resistance of low‐alloy steel in 10 wt% sulfuric acid solution

The aqueous corrosion behavior of low‐alloy steel with aluminum contents was examined in a 10 wt% H₂SO₄ (pH 0.13) solution using electrochemical techniques and surface analyses. The corrosion resistance of the new alloy steel was evaluated in terms of electrochemical parameters, such as passive current density, film, and charge transfer resistances. The results showed that a high Al content in the steel imparted better passivation behavior resulting in a lower corrosion rate. It related to the enrichment of iron carbonate and hydrocarbon by the dissolution of the carbide phase.     

The characterization of patina components by X-ray diffraction and evolved gas analysis

Fourteen patinated copper specimens, seven each from the Statue of Liberty, New York Habor and from roofs at AT&T Bell Laboratories in Murray Hill, NJ, ranged in atmospheric exposure from 1 to 100 years. X-ray diffraction showed the presence of cuprite, Cu₂O, and brochantite, Cu₄(SO₄)(OH)₆, in all specimens and antlerite, Cu₃(SO₄)(OH)₄ (up to 0.7 times brochantite), atacamite, Cu₂Cl(OH)₃ (up to 1.6 times brochantite), and/or posnjakite, Cu₄(SO₄)(OH)₆ · 2H₂O (up to 5.2 times brochantite) in some. Posnjakite has been previously reported as a patina component only once during short term exposures in Eurasia. It appears to be an early corrosion product which subsequently converts to brochantite. Mass spectrographic examination of gases emitted from heated patinas provides further information on patina composition, in particular on the presence of both carbonate and oxalate in widely varying ratios.     

Environmental factors affecting the corrosion behaviour of reinforcing steel. V. Role of chloride and sulphate ions in the corrosion of reinforcing steel in saturated Ca(OH)2 solutions

The corrosion behaviour of reinforcing steel in saturated naturally aerated Ca(OH)₂ solutions in absence and presence of different concentrations of NaCl, NH₄Cl, Na₂SO₄ and (NH₄)₂SO₄ is followed by measuring of the open circuit potential complemented with SEM and EDS investigation. These salts cause breakdown of passivity and initiation of pitting corrosion. The rates of oxide film thickening by OH⁻ ions and oxide film destruction by the aggressive ions follow a direct logarithm law and depend on the concentration and type of aggressive salts anions and cations. The values of the activation energies for oxide film thickening are calculated and discussed.     

Outdoor atmospheric corrosion of copper in Saudi Arabia

Abstract

Copper specimens have been exposed to the action of marine, marine industrial, urban and rural atmospheres of Saudi Arabia. Environmental factors such as average temperature, average relative humidity and deposition rates of atmospheric pollutants (i.e. Cl^- and SO₂) was investigated. By applying the standard ISO 9223, the aggressiveness of the atmospheres corresponding to the different test stations has been determined. Calculations of corrosion rates were made via loss of weight after one, two and three years of exposure and characterisation of the corrosion products formed on samples have been analysed using X-ray diffraction. Three main sequences have been identified on outdoor copper, representing different reaction routes in chloride dominated environments. Many kinds of patina were found on copper specimens such as cuprite (Cu₂ O), atacamite (Cu₂ Cl(OH)₃), paratacamite (Cu₂ (OH)₃Cl), copper amine nitrite hydroxide, gerhardite, copper hydroxide nitrate and copper amine nitrate.     

Mechanistic studies of corrosion product flaking on copper and copper-based alloys in marine environments

The mechanism of corrosion product flaking on bare copper sheet and three copper-based alloys in chloride rich environments has been explored through field and laboratory exposures. The tendency for flaking is much more pronounced on Cu and Cu–4 wt%Sn than on Cu–15 wt%Zn and Cu–5 wt%Al–5 wt%Zn. This difference is explained by the initial formation of zinc and zinc–aluminum hydroxycarbonates on Cu15Zn and Cu5Al5Zn, which delays the formation of CuCl, a precursor of Cu₂(OH)₃Cl. As a result, the observed volume expansion during transformation of CuCl to Cu₂(OH)₃Cl, and concomitant corrosion product flaking, is less severe on Cu15Zn and Cu5Al5Zn than on Cu and Cu4Sn.     

Evolution of patinas on copper exposed in a suburban area

Copper plates were exposed under sheltered outdoor conditions for up to one year, starting in September 2001 in Musashino City, Tokyo, a suburban area. Following various periods of exposure, the patinas on the plates were characterized to investigate their evolution by using X-ray fluorescence analysis, X-ray diffraction, field emission scanning electron microscopy, and glow discharge optical emission spectroscopy. The difference in the roles of sulfur and chlorine in the early stages of copper patination were identified by analyzing the depth profiles of these two elements. Sulfur was found on top of the patina as cupric sulfates such as posnjakite (Cu₄SO₄(OH)₆ · H₂O) or brochantite (Cu₄SO₄(OH)₆). Brochantite appeared only after 12 months of exposure. In contrast, chlorine was found on the surface after only one month of exposure. It gradually penetrated the patina as the exposure period lengthened, forming copper chloride complexes. Chloride ions accumulated at the patina/copper interface, forming nantokite (CuCl), which promoted corrosion.