Corrosion of copper and silver plates by volcanic gases

Corrosion products that had been formed on copper and silver plates exposed in Miyake Island, where suffered a volcanic eruption in 2000, were analyzed by X-ray techniques to get better understanding of copper and silver corrosion in harsh environment. The exposure experiment was carried out from September 2004 to April 2005. Many kinds of patina were found on copper such as cuprite (Cu₂O), posnjakite (Cu₄SO₄(OH)₆ · H₂O), brochantite (Cu₄SO₄(OH)₆), antlerite (Cu₃SO₄(OH)₄), and geerite (Cu₈S₅). For silver, silver chloride (AgCl) and silver sulfide (Ag₂S) were formed. Although the volcanic activity had greatly subsided, the atmospheric corrosion of copper and silver plates exposed on Miyake Island was mainly affected by volcanic gases, wet-dry cycles in the environment, and sea-salt aerosols.     

Effects of NaCl and SO2 on the initial atmospheric corrosion of zinc

The influence of NaCl deposition on the corrosion of zinc in atmospheres with and without SO₂ was studied via quartz crystal microbalance. Regularity of the initial corrosion of zinc under these conditions was analyzed. The results show that NaCl can accelerate the corrosion of zinc. Mass gain of zinc increases with the exposure time, which can be correlated by using exponential decay function. The relationship between mass gain and amount of NaCl deposition is well linear at any time in air containing 1 ppm SO₂, but follows quadratic function in air without SO₂. More amount of NaCl deposition will slow down the corrosion to some extent after exposure for certain time in the presence of SO₂. The combined effect of NaCl and SO₂ on the corrosion of zinc is greater than that caused by each single component. Fourier transform infrared spectroscopy and X-ray diffraction were used to characterize the corrosion products of zinc. In the absence of SO₂, simonkolleite, Zn₅(OH)₈Cl₂·H₂O and zincite, ZnO are the dominant corrosion products, while zinc hydroxysulfate (Zn₄SO₄(OH)₆·3H₂O), zinc chloride sulfate hydroxide hydrate (Zn₁₂(SO₄)₃Cl₃·(OH)₁₅·5H₂O) and simonkolleite dominate in the presence of SO₂. Brief discussion on the mechanisms of atmospheric corrosion under these conditions was introduced.     

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.     

Chemistry of corrosion products on Zn-Al-Mg alloy coated steel

Zn-Al-Mg alloy (ZM) coating provides a decisively enhanced corrosion resistance in a salt spray test according to DIN EN ISO 9227 (NSS) compared to conventional hot-dip galvanised zinc (Z) coating because of its ability to form a very stable, well adherent protecting layer of zinc aluminium carbonate hydroxide, Zn₆Al₂(CO₃)(OH)₁₆·4H₂O on the steel substrate. This protecting layer is the main reason for the enhanced corrosion resistance of the ZM coating. Surface corrosion products on ZM coated steel consist mainly of Zn₅(OH)₆(CO₃)₂, ZnCO₃ and Zn(OH)₂ with additions of Zn₅(OH)₈Cl₂ · H₂O and a carbonate-containing magnesium species.     

Corrosion behaviour of die-cast AZ91D magnesium alloy in aqueous sulphate solutions

The corrosion behaviour of die-cast AZ91D magnesium alloys in sulphate solutions was investigated by SEM, FTIR and polarization measurements. For immersion times less than 48 h, no pitting corrosion occurred and only generalized corrosion was apparent. According to the polarization curves, the corrosion rate order of the die-cast AZ91D Mg alloy in three aqueous solutions was: NaCl > MgSO₄ > Na₂SO₄. The main corrosion products were Mg(OH)₂ and MgAl₂(SO₄)₄·22H₂O in the sulphate solutions and the product film was compact. Precipitation of MgAl₂(SO₄)₄·22H₂O required a threshold immersion time.     

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.     

Effects of NaCl and NH4Cl on the initial atmospheric corrosion of zinc

Effects of NaCl and NH₄Cl on the initial atmospheric corrosion of zinc were investigated via quartz crystal microbalance (QCM) in laboratory at 80% RH and 25 °C. The results show that both NaCl and NH₄Cl can accelerate the initial atmospheric corrosion of zinc. The combined effect of NaCl and NH₄Cl on the corrosion of zinc is greater than that caused by NH₄Cl and less than that caused by NaCl. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy and electron dispersion X-ray analysis (SEM/EDAX) were used to characterize the corrosion products of zinc. (NH₄)₂ZnCl₄, Zn₅(OH)₈Cl₂ · H₂O and ZnO present on zinc surface in the presence of NH₄Cl while Zn₅(OH)₈Cl₂ · H₂O and ZnO are the dominant corrosion products on NaCl-treated zinc surface. Probable mechanisms are presented to explain the experimental results.     

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.     

A study of the corrosion products of aluminum brass formed in sodium sulfate solution in the presence of chlorides

The surface film forming on Al brass specimens immersed in stagnant Na₂SO₄ solutions containing chlorides at pH values 3.0–7.25 was examined by using chemical, electrochemical and X-ray techniques. In the absence of chlorides the surface film consists of oxides (CuO, Cu₂O) and cupric basic sulfates Cu₃(SO₄)₂.4H₂O, stable in the whole range of pH; the surface film is quite homogeneous and no dezincification or localized corrosion occurs. In the presence of chlorides, the surface film consists also of cuprous chloride (CuCl) and of cupric [Cu(OH,Cl)₂.2H₂O] and aluminum oxychlorides [Al₄₅O₄₅(OH)₄₅Cl] and aluminum oxides (Al(OH)₃]. The weight of the corrosion products is a maximum in solutions containing 5 × 10⁻³ M NaCl at each pH value. In the most acidic solutions the surface film is physically and chemically extremely unhomogeneous, thus favouring the occurrence of dezincification or localized corrosion phenomena.     

Corrosion product formation on Zn55Al coated steel upon exposure in a marine atmosphere

The formation of corrosion products on Zn55Al coated steel has been investigated upon field exposures in a marine environment. The corrosion products consisted mainly of zinc aluminium hydroxy carbonate, Zn_0.71Al_0.29(OH)₂(CO₃)_0.145·xH₂O, zinc chloro sulfate (NaZn₄(SO₄)Cl(OH)₆·6H₂O), zinc hydroxy chloride, Zn₅(OH)₈Cl₂·H₂O and zinc hydroxy carbonate, Zn₅(OH)₆(CO₃)₂ were the first three phases were formed initially while zinc hydroxy carbonate Zn₅(OH)₆(CO₃)₂ was formed after prolonged exposure in more corrosive conditions. The initial corrosion product formation was due to selective corrosion of the zinc rich interdendritic areas of the coating resulting in a mixture of zinc and zinc aluminium corrosion products.     

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.     

The temperature-dependence of the SO2-induced atmospheric corrosion of zinc; a laboratory study

The SO₂-induced atmospheric corrosion of zinc was studied at 4, 14, 22 and 30 °C and 95% RH. Each sample was exposed individually to synthetic atmospheres with careful control of SO₂ concentration (107 and 500 ppb), relative humidity and flow conditions. The initial reaction between SO₂ and zinc was studied in a time-resolved manner. Two-week exposures were performed to measure the corrosion rate and study the formation of corrosion products. Corrosion products were analysed by X-ray powder diffraction and ion chromatography. The corrosion rate was inversely dependent on temperature, the maximum rate being found at the lowest temperature. SO₂ deposition showed a similar trend with the highest deposition rate at 4 °C. At low temperature a thick film of ZnSO₄(aq) formed on the metal surface, whereas zinc hydroxysulphate (ZnSO₄ · 3Zn(OH)₂ · 4H₂O(s)) was the main corrosion product at 22 and 30 °C. The inverse temperature-dependence of the corrosion rate of zinc is proposed to be connected to the formation of sparingly soluble zinc hydroxy sulphate which slows down the deposition of SO₂ on the surface.     

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.     

Initial NaCl-particle induced atmospheric corrosion of zinc—Effect of CO2 and SO2

Initial corrosion and secondary spreading effects during NaCl particle induced corrosion on zinc was explored using in situ and ex situ FTIR microspectroscopy, optical microscopy, and SEM/EDAX. The secondary spreading effect which occurs upon introduction of humid air on NaCl deposited zinc surfaces was strongly dependent on the CO₂ and SO₂ content of the introduced air. Ambient level of CO₂ (350 ppm) resulted in a relatively low spreading effect, whereas the lower level of CO₂ (<5 ppm) caused a much faster spreading over a larger area. In the presence of SO₂, the secondary spreading effect was absent which could limit the cathodic process in this case. At <5 ppm CO₂, the corrosion is more localized, with the formation of simonkolleite (Zn₅(OH)₈Cl₂ · H₂O), zincite (ZnO) and sodium carbonate (Na₂CO₃), and a larger effective cathodic area. At 350 ppm CO₂, the corrosion is more general and formation of simonkolleite, hydrozincite (Zn₅(OH)₆(CO₃)₂) and sodium carbonate was observed. Sodium carbonate was mainly formed in more alkaline areas, in the inner edge of the electrolyte droplet and in the secondary spreading area. Oxidation of sulphur and concomitant sulphate formation was enhanced in the presence of NaCl particles, due to the formation of a droplet, the separation of the anodic and cathodic areas and the accompanying differences in chemical composition and pH in the surface electrolyte.     

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.     

Differences between corrosion products formed on copper exposed in Tokyo in summer and winter

We analyzed the copper corrosion products that formed during a month in summer and a month in winter at three sites in Tokyo using several analytical techniques. The X-ray diffraction patterns revealed that cuprite Cu₂O and posnjakite Cu₄SO₄(OH)₆·H₂O formed on copper exposed in summer. By contrast, only cuprite was found in winter exposed copper. The X-ray fluorescence results indicated that the amounts of sulfur and chlorine on the copper plates exposed in summer were much greater than those in winter. This could be explained by the change in particulate sulfate and sea salt concentrations. Depth profiling analysis by Auger electron spectroscopy revealed that the oxide layer formed in summer was thicker than that in winter. This difference in oxide layer thickness could have been due to the differences in temperature, relative humidity, and the amount of sulfur and chlorine on the copper plate.     

Initial atmospheric corrosion of zinc in presence of Na2SO4 and （NH4）2S04

Initial atmospheric corrosion of zinc in the presence of Na₂SO₄ and (NH₄)₂SO₄ was investigated via quartz crystal microbalance(QCM) in laboratory at relative humidity(RH) of 80% and 25 °C. The results show that both Na₂SO₄ and (NH₄)₂SO₄ can accelerate the initial atmospheric corrosion of zinc. The combined effect of Na₂SO₄ and (NH₄)₂SO₄ on the corrosion of zinc is greater than that caused by (NH₄)₂SO₄ and less than that caused by Na₂SO₄. Fourier transform infrared spectroscopy(FTIR), X-ray diffractometry(XRD) and scanning electron microscopy(SEM) were used to characterize the corrosion products of zinc. (NH₄)₂Zn(SO₄)₂, Zn₄SO₄(OH)₆·5H₂O and ZnO present on zinc surface in the presence of (NH₄)₂SO₄ while Zn₄SO₄(OH)₆·5H₂O and ZnO are the dominant corrosion products on Na₂SO₄-treated zinc surface. Probable mechanisms are presented to explain the experimental results.     

Studies of galvanised steel atmospheric corrosion in Saudi Arabia

Abstract

This paper summarises the results obtained for galvanised steel specimens exposed in Saudi Arabia region for four years at four pure marine and five mixed marine (SO₂ polluted) sites. The atmospheres at these sites were characterised climatologically and in terms of their pollution level so that their corrosivity could be expressed in accordance with ISO standards. Chemical characterisation of the galvanised steel corrosion product layers was performed using X-ray diffraction. The main phases determined were zincite (ZnO), simonkolleite [Zn₅(OH)₈Cl₂.H₂O], smithsonite (ZnCO₃), magnetite (Fe₃O₄), gordaite [NaZn₄(SO₄)Cl(OH)₆Cl.6(H₂O)], hematite (Fe₂O₃), zinkosite (ZnSO₄), zinc chloride (ZnCl₂), zinc hydroxide sulphate hydrate [(Zn(OH)₂)₃(ZnSO₄)(H₂O)₃] and zinc sulphate hydroxide hydrate [ZnSO₄(OH)₂.5H₂O] was found on the specimens. The results obeyed well with the empirical kinetics equation of the form C?=?Ktⁿ, where K and C are the corrosion losses in mg cm^?2 after 1 and ‘t’ years of the exposure respectively, and ‘n’ is constant. Based on ‘n’ values, the corrosion mechanism of galvanised steel is predicted. The results obtained show that the corrosion rate of galvanised steel is a function of both the chloride, SO₂ pollution level and the humidity. Corrosion rate of galvanised steel specimens have been obtained by loss of weight after each year of exposure.     

One-step synthesis and properties of monolithic photoluminescent ruby colored cuprous oxide antimony oxide glass nanocomposites

Cuprous oxide (Cu₂O) antimony glass (K₂O-B₂O₃-Sb₂O₃) monolithic nanocomposites having brilliant yellow to ruby red color have been synthesized by a single-step melt-quench technique involving in situ thermochemical reduction of Cu²⁺ (CuO) by the reducing glass matrix without using any external reducing agent. The X-ray diffraction (XRD), infrared transmission and reflection spectra, and selected area electron diffraction analysis support the reduction of Cu²⁺ to Cu⁺ with the formation of Cu₂O nanoclusters along with Cu_ySb_2−x(O,OH)_6-7 (y ≤ 2, x ≤ 1) nanocrystalline phases while Cu⁰ nanoclusters are formed at very high Cu concentration. The UV-vis spectra of the yellow and orange colored nanocomposites show size-controlled band gap shift of the semiconductor (Cu₂O) nanocrystallites embedded in the glasses while the red nanocomposite exhibits surface plasmon resonance band at 529 nm due to metallic Cu. Transmission electron microscopic image advocates the formation of nanocystallites (5-42 nm). Photoluminescence emission studies show broad red emission band around 626 nm under various excitation wavelengths from 210 to 270 nm.     

The effects of air pollution and climatic factors on atmospheric corrosion of marble under field exposure

The atmospheric corrosion of marble was evaluated in terms of SO₂ concentration as air pollution and climatic factors such as rainfall, relative humidity, temperature and so on under the field exposure. Marble of calcite type (CaCO₃) was exposed to outdoor atmospheric environment with and without a rain shelter at four test sites in the southern part of Vietnam for 3-month, 1- and 2-year periods from July 2001 to September 2003. The thickness loss of marble was investigated gravimetrically. X-ray diffraction and X-ray fluorescent methods were applied to study corrosion products on marble. The corrosion product of marble was only gypsum (CaSO₄ · 2H₂O) and was washed out by rain under the unsheltered exposure condition. It was found that the most substantial factors influencing the corrosion of marble were rainfall, SO₂ concentration in the air and relative humidity. Based on the results obtained, we estimated the dose-response functions for the atmospheric corrosion of marble in the southern part of Vietnam.