The corrosion of copper by atmospheric sulphurous gases

The sulfurization of copper by atmospheric gases is widely recognized, but the importance of the potential causative agents of sulfurization and the mechanisms involved have remained unresolved. In this work, polycrystalline copper has been exposed to the atmospheric gases hydrogen sulfide (H₂S), carbonyl sulfide (OCS), carbon disulfide (CS₂), and sulfur dioxide (SO₂) in humidified air under carefully controlled laboratory conditions. At room temperature, the rates of sulfurization by H₂S and OCS are comparable, and are some two orders of magnitude greater than those by CS₂ and SO₂. Given the atmospheric concentrations of these gases, it is clear that OCS is the principal cause of atmospheric sulfurization of copper except near sources of the gases where high concentrations may render H₂S (and possibly SO₂) important. At constant absolute humidity, the sulfurization rate of copper by OCS is found to be inversely proportional to temperature over the range 21–80°C, a property attributed to reduced quantities of surface water at high temperatures and the subsequent decrease in the rate of hydrolytic transformation of OCS into a reactive form. In a final series of experiments, the initial sulfurization of copper by 2.2 ± 0.2 ppm H₂S in humidified air at 22°C has been studied in detail. The first stages of sulfurization involve rapid attack by H₂S at surface defect sites. As these corrosive mounds spread and merge, diffusion of copper to the surface is impeded and the fraction of H₂S molecules striking the surface that become incorporated into the corrosion film drops sharply from ～ 5 × 10^?5 (at t = 5 s) to ～ 8 × 10^?7 (at t = 72 h).     

On the atmospheric corrosion of thin copper films

Sputtered and electrodeposited copper specimens were exposed to the laboratory atmosphere for 18 months, after which the corrosion products were analysed by electrochemical methods and reflectance spectra. The formation of corrosion products takes place in three stages: initially cuprous oxide is formed, followed by the growth of cuprous sulphide, and finally cuprous oxide is converted to cuprous sulphide. The presence of water is essential for these corrosion reactions to occur.     

The influence of sodium chloride on the atmospheric corrosion of steel

The influence of sodium chloride on the atmospheric corrosion of mild steel has been studied. Samples covered with sodium chloride crystals (8 m?g NaCl · cm^?2) have been exposed to an SO₂-free atmosphere at different relative humidities. The combined effect of sodium chloride crystals on a steel surface and sulphur dioxide in the atmosphere has been investigated at an SO₂-supply of 1 m?g SO₂ · cm^–2 · h^–1 (1 ppm SO₂). The corrosion attack was followed by periodic weighings. The corrosion products formed have been studied using the SEM-technique. On exposure of samples with sodium chloride in an SO₂-free atmosphere the extent of corrosion increased with increasing relative humidity from 58% to 90%, interrupted by a sharp minimum at about 87% relative humidity. The SEM-studies showed that tower shaped corrosion products were formed at a high relative humidity while filiform corrosion appeared when the relative humidity was lowered. At 90% relative humidity more corrosion was observed with clean steel samples and an SO₂-supply of 1 m?g ·cm^–2 ·h^–1 than with sodium chloride crystals on the surfaces (8 m?g NaCl ·cm^–2) in the absence of SO₂. In the combined influence of sodium chloride on the steel surfaces and sulphur dioxide in the atmosphere a synergic effect was noticed at 90% relative humidity. At 70% relative humidity no influence of an SO₂-supply of 1 m?g SO₂ ·cm^–2 ·h^–1 on the corrosion of steel samples with sodium chloride crystals on their surfaces could be observed.     

The influence of airborne salinity on the atmospheric corrosion of steel

A model of the influence of chloride deposition rate and SO₂ deposition rate on atmospheric corrosion of steel has been proposed. Accumulated corrosion and pollution data obtained since 1979 from different Cuban sites were statistically processed. A model is obtained when data from all corrosion stations are processed independently of the type of climatic territory. The influence of chloride ions is very significant in determining corrosion rate when there is already a corrosion products layer; however, when this layer is not completely formed the influence of time of wetness is the controlling factor. The existence of a competitive adsorption process between chloride and sulphur compounds present in airborne salinity is very possible.     

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.     

The atmospheric corrosion of copper by hydrogen sulphide in underground conditions

The atmospheric corrosion of copper by hydrogen sulphide has been followed during field tests using different sulphide concentrations, for 77 days, and during exposure to a well-defined synthetic atmosphere in a test chamber. The main components formed at the surface of the samples are copper oxides and sulphide. We show that exposure tests performed for short times in synthetic atmospheres cannot be extrapolated to long time exposure in real conditions, since three successive phases of film growth are observed. The mechanism of film growth is discussed, assuming that cationic diffusion through the cuprous oxides and sulphide is the rate-determining step.     

Runoff of copper and zinc caused by atmospheric corrosion

Runoff and total corrosion loss for copper and zinc were investigated at seven sites in Switzerland. The exposure sites were chosen near the stations of the National Air Pollution Monitoring Network (NABEL), where climatic and air pollution data are measured. Runoff and corrosion rates were investigated after 0.5, 1, 2 and 4 years of exposure. Runoff rates differ from corrosion rates depending on the material, the exposure time and the sampling site.     

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.     

The influence of adenine on corrosion of copper in chloride solutions

The influence of the concentration of adenine (AD) on the corrosion and the spontaneous dissolution of copper in 1.0 M NaCl solutions of pH 6.8 was studied. The investigations involved electrochemical polarization methods as well as weight loss measurements, quartz crystal microbalance (QCM) techniques and scanning electron microscopy (SEM). The inhibition efficiency increases with an increase in the concentration of AD. An adherent layer of inhibitor is postulated to account for the protective effect. The adsorption of adenine has been found to occur on the surface of copper according to the Langmuir isotherm. The values of standard free energies of adsorption suggest chemical adsorption of AD on copper surface. The use of adenine can effectively prevent various new installations made of copper and exposed to the action of aqueous solutions of chlorides from corrosion damage.     

The atmospheric corrosion of iron as studied by Mössbauer spectroscopy

The composition of the rust on the surface of steel panels was determined after atmospheric exposure times of 2 weeks, 2 months and 6 months. The initial product is γ-FeOOH which converts in time to a mixture of α-FeOOH and γ-Fe₂O₃. Steel exposed for times of the order of 25 years is covered with corrosion product consisting largely of γ-Fe₂O₃. The similarity between the composition of the corrosion products and precipitates formed from FeSO₄ solution under mildly acidic conditions at 90°C suggests that the dominant anion in these atmospheric corrosion experiments is sulfate.     

The influence of nickel and copper on the austempering of ductile iron

In the present investigation, the effect of alloying elements on the austempering process, austempered microstructure, and structural parameters of two austempered ductile irons (ADI) containing 0.6% Cu and 0.6% Cu/1.0% Ni as the main alloying elements was investigated. The optical metallography and x-ray diffraction were used to study the changes in the austempered structure. The effect of alloying additions on the austempering kinetics was studied using the Avrami equation. Significantly more upper bainite was observed in the austempered Cu-Ni alloyed ADI than in Cu alloyed ADI. The volume fraction of retained austenite (X _γ), the carbon level in the retained austenite (C _γ), and the product X _γ C _γ in an austempered structure of Cu-alloyed ADI are higher than in Cu-Ni-alloyed ADI. The austempering Kinetics is slowed down by the addition of Ni.     

The atmospheric corrosion of copper at two sites in Portugal: a comparative study

This paper presents a comparative study on the atmospheric corrosion of copper, at two sites, in Portugal, with exposures started in two different seasons (summer and winter). Particular attention is devoted to the initial stages of the corrosion process.The levels of pollutants, namely of SO₂ and chlorides, in both atmospheres, have been measured, over the periods from August 1999 to July 2000 and from November 2000 until July 2001. Climatic data for both sites and both periods has been collected and analysed.Kinetics of the corrosion process (weight losses) have shown to be described by: Δm=kt^0.6 and Δm=kt^0.4, with k equal to 3.4 (g m⁻² month^−0.6) and 17 (g m⁻² month^−0.4), for the one year exposures, started in summer, at the urban and maritime atmospheres, respectively. Exposures started in winter, at the urban atmosphere, have lead to kinetics described by Δm=kt^0.7 with k=5.0 (g m⁻² month^−0.7).The chemical composition and the morphology of the copper patinas, corresponding to exposures of 2 and 12 months, at the two sites, are compared as well as the morphology of the corroded surfaces.     

Degradation of galvanised iron roofing material in Tanzania by atmospheric corrosion

Abstract

Galvanised iron is popular in many applications, particular as a roofing material. However, just like other materials, especially metallic ones, it is prone to degradation by corrosion. In this particular study, the degradation of galvanised roof sheets was investigated at a coastal, urban and rural site in Tanzania, Africa. Samples were exposed to various outdoor environments over a period of 3 years. In addition, some accelerated laboratory investigations were conducted in different simulated air pollution environments in an artificial corrosion chamber constructed for this purpose to supplement the outdoor exposure tests. It was found that the combination of the tropical climate and increasing air pollution due to industrial development in the capital Dar-es-Salaam resulted in substantial atmospheric corrosion of the roof sheets, which eventually leads to failure and the necessity for replacement. The rural site had the lowest degree of atmospheric corrosion as expected. A combination of different corrosion products was identified as a result of the atmospheric corrosion by Raman and EDX analyses. The information gained from this investigation could be utilised to construct more durable structures requiring less frequent replacement and maintenance in future.     

Advances in understanding atmospheric corrosion of iron. I. Rust characterisation of ancient ferrous artefacts exposed to indoor atmospheric corrosion

Metallic substrates and rust layers of several hundred year old (y.o.) ferrous artefacts were characterised. Composition, structure and porosity of the rust were analysed by different methods: OM, SEM, EDS, EPMA, XRD, μXRD, SAXS, BET and mercury porosimetry.Several important parameters to describe an old rust layer were determined and measured. These parameters will be used for the modelling of long-term indoor atmospheric corrosion.     

The influence of ion implantation on the corrosion behaviour of iron in acid solution

The influence of ion implantation on the aqueous corrosion of pure iron in IN H₂SO₄ was studied. The iron was bombarded with 5 × 10¹⁵–10¹⁷ ions.cm^?2 of Ne, Ar, Cu, Pb and Au. The current density-potential curves of the implanted samples were measured and compared with that of untreated pure iron. Ne⁺ and Cu⁺ bombardments lead to a slightly higher corrosion rate in comparison with untreated iron. Pb⁺ depressed the corrosion rate by orders of magnitude, Au⁺ enhanced it by a factor of more than ten. The effect is attributed to a reduction or an increase of the activity of the electrode surface with respect to the cathodic hydrogen evolution reaction, i.e. the ion implantation influences strongly the exchange current density of the hydrogen evolution reaction. A marked influence of the implantation on the anodic behaviour of the corroding metal could also be observed.     

Use of the gold markers method to predict the mechanisms of iron atmospheric corrosion

Iron corrosion under atmospheric conditions has been investigated by using the gold markers method. The corrosion experiments were performed in a climatic chamber with an accelerated treatment. The gold markers localization, carried out by scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, revealed that the rust layer growth was essentially due to an internal development. Moreover, microRaman mappings allowed prediction of the mechanism of rust layer evolution during the ageing treatment. Finally these results were compared to samples corroded for several 100 years in order to extrapolate our observations to long term corrosion.     

The influence of pH value on the efficiency of imidazole based corrosion inhibitors of copper

The aim of this work is to establish the correlation between the solution pH and the inhibiting efficiency of two imidazole compounds (4-methyl-1-phenyl imidazole and 4-methyl-1-(p-tolyl) imidazole) in protection of copper from corrosion in chloride media.It was found that the inhibiting efficiency of both studied imidazoles enhances with the increase of the solution pH value, from about 20% in 0.5 M HCl to 92% in 0.5 M NaCl. This improvement was ascribed to stronger adsorption of neutral imidazole molecule, which can be expected at higher pH values, than that of the protonated imidazole cation, which may be expected in acid solutions.     

The influence of relative humidity and temperature on the acetic acid vapour-induced atmospheric corrosion of lead

The acetic-acid induced atmospheric corrosion of lead was studied at 22.0 °C and 30-95% RH and at 4 °C and 95% RH. The samples were exposed to synthetic air with careful control of relative humidity, temperature, acetic acid concentration (170 ppb) and flow conditions. Reference exposures were carried out in clean humid air. Samples were analysed by gravimetry, ion chromatography, quantitative carbonate analysis, ESEM and XRD. Traces of acetic acid vapour strongly accelerate the atmospheric corrosion of lead. The corrosion rate is only weakly dependent on relative humidity in the range 95-50% RH. The accumulated amount of acetate is independent of RH in the range 95-40%. Lead corrosion in humid air in the presence of acetic acid vapour exhibits a negative correlation with temperature. The crystalline corrosion products formed on lead in the presence of acetic acid vapour were lead acetate oxide hydrate (Pb(CH₃COO)₂ · 2PbO · H₂O) and massicot (β-PbO) together with plumbonacrite (Pb₁₀O(CO₃)₆(OH)₆) or hydrocerussite (Pb₃(CO₃)₂(OH)₂). The transformation of lead acetate oxide hydrate into hydrocerussite and vice versa was also studied. The mechanism of corrosion is addressed, and the implications of this study for combating the corrosion of lead organ pipes in historical organs are discussed.