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.     

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.     

Copper patinas: an investigation by Auger electron spectroscopy

Auger electron spectroscopy in conjunction with Ar⁺ sputtering has been used to investigate four samples of copper that have been patinated by exposure to the atmosphere for periods ranging from 1 to 100 years. The elemental depth profiles were qualitatively similar for all samples. The patinas were covered with a thin layer of carbon containing species and consisted primarily of copper, sulfur, chlorine, and oxygen. The sulfur is present primarily near the surface of the patina and the chlorine is distributed throughout the patina. In two samples, 44 and 100 years old, significant amounts of chlorine were found in the portion of the patina nearest the bulk copper. A simple mass balance shows that the surface of the patina (beneath the carbon containing layer) is composed primarily of the mineral brochantite, Cu₄(SO₄)(OH)₆, as expected thermodynamically. A thermodynamic analysis also shows that atacamite, Cu₂Cl(OH)₃, the principal chlorine containing mineral found in the patinas, can be stable with respect to cuprite, Cu₂O, particularly in the immediate vicinity of unoxidized copper.     

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.     

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.     

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.     

Morphological study of 16-year patinas formed on copper in a wide range of atmospheric exposures

Much information is available on the atmospheric corrosion of copper and patina formation mechanisms in the short, mid and even long term. However, studies of the structure and morphology of patina layers are less abundant and mostly deal with patinas formed in the atmosphere over a small number of years. The present study concentrates on the structure and morphology of corrosion product films formed on copper after long-term atmospheric exposure (13-16 years) in five Spanish atmospheres of different types: rural, urban, industrial and marine (mild and severe). Characterisation has been performed by X-ray diffraction (XRD) and scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS). Long-term copper corrosion is higher in industrial and marine atmospheres and lower in rural and urban atmospheres. In all cases a decrease in the corrosion rate with exposure time is observed. The formation of antlerite [Cu₃SO₄(OH)₄] is seen in more acidic conditions and in specimen areas subject to a high time of wetness. The presence of nantokite (CuCl), which is not generally mentioned in field studies, has been detected under the cuprite layer very close to the base copper.     

Corrosion characteristics of copper microparticles and copper nanoparticles in distilled water

The corrosion characteristics of copper microparticles and copper nanoparticles in distilled water were investigated in this paper. The Cu²⁺ transformations of copper microparticles and copper nanoparticles in distilled water were tested by using absorbance measurement, the structures of their corrosion products were determined by using XRD and TEM techniques. The results of absorbance measurement show that the corrosion characteristics of copper nanoparticles in distilled water are quite different from that of copper microparticles. The Cu²⁺ transformations ratio of copper microparticles increases slowly with the increasing of immersion time and levels off eventually, but the Cu²⁺ transformations ratio of copper nanoparticles increases sharply with the increasing of immersion time and gets to peak rapidly, and then decreases as the immersion time increases and levels off finally. The results of XRD present that they have different corrosion products, the corrosion products of copper microparticles in distilled water are Cu and CuO, but the nanoparticles are Cu, CuO, Cu(OH,Cl)₂ · 2H₂O and Cu₂(CO₃)(OH)₂. All these differences owe to the size effect of copper particles.     

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 of bronze by acetic and formic acid vapours,sulphur dioxide and sodium chloride particles

This paper studies the corrosion of patinated and unpatinated bronze by acetic and formic acid vapours, sulphur dioxide and sodium chloride salt particles, at 100% relative humidity. Weight loss, X-ray diffraction, infrared and scanning electron microscopy were the techniques used. Acetic and formic acid vapours, sulphur dioxide and sodium chloride produce a high corrosion rate on bronze. In general, no protective effect was found by the patina on bronze. The principal compounds identified were Cu₂O, Cu₂S, Cu₅(SO₄)₂(OH)₆ · 5H₂O, Cu(CH₃CO₂)₂ · XH₂O and Cu(HCO₂)2.     

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.     

The effect of synthetic zinc corrosion products on corrosion of electrogalvanized steel. II. Zinc reactivity and galvanic coupling zinc/steel in presence of zinc corrosion products

The reactivity of zinc under synthetic zinc patinas and the galvanic coupling in steel/patina/Zn are studied. Zn₅(OH)₆(CO₃)₂ and Na₂Zn₃(CO₃)₄⋅3H₂O inhibit zinc anodic dissolution in NaCl, while Zn₅(OH)₈Cl₂ H₂O and Zn₄(OH)₆SO₄ nH₂O do not. The galvanic current in steel/patina/NaCl/Zn is smaller as compared to steel/NaCl/Zn. The inhibiting effect decreases with time for Na₂Zn₃(CO₃)₄⋅3H₂O or Zn₄(OH)₆SO₄ nH₂O due to the transformation into Zn(OH)₂. In NaHCO₃, the polarity between zinc and steel can reverse. The effect of confinement on the cathodic current is stronger than the initial effect of patina which is explained by the instability of the patinas under rapid pH-increase.     

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.     

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.     

可降解血管支架用Mg-4.0Zn-0.2Mn-0.2Ca微细管的体外降解行为

通过浸泡实验和电化学测试研究了Mg-4.0Zn-0.2Mn-0.2Ca（质量分数）微细管的体外降解行为与腐蚀机理。结果表明,退火处理可以提高微细管的耐腐蚀性。长期浸泡实验表明腐蚀过程相对均匀,退火微细管在Hank''s溶液中的腐蚀速率约为0.30 mm/a。在浸泡初期,退火管材表面生成Mg(OH)₂,形成保护膜,阻碍腐蚀进行。虽然Mg(OH)₂膜上形成的羟基磷灰石（HA）可以进一步降低腐蚀速率,但是镁基体中粗大的第二相会增强电偶腐蚀效应,并且生成的大量氢气,从而破坏HA膜,使腐蚀继续进行。     

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.     

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.     

Characterization of corroded bronze Ding from the Yin Ruins of China

This paper presents the result of scientific examinations carried out on the soil-buried archaeological bronzes Ding from Yin Ruins of China. Eight of typical fragments from different bronze Ding were selected as researched samples according to their deterioration characteristics. Optical microscopy (OM), scanning electron microscopy coupled with energy (SEM-EDX), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) were used to understand the corrosive morphological characteristics, to clear the nature of patina and to analyze the elementary composition of bronze Ding. The results indicated that it is not possible to distinguish the original lustrous metallic surface in most samples because of the corrosive crust. The substrate of bronze Ding contains74-86% Cu, 1.1-4.6% Pb, and 10-18% Sn, which is in agreement with the historical investigation in the ritual vessels of Shang time. Copper-containing compounds were the main constituents of natural patina: Cu₂(OH)₃Cl existed as corrosion product in all the powdery or crack surface; Cu₂(OH)₂CO₃ was the main corrosive product in a compact and hard corrosive surface. This study provides useful information for the restoration and protection of bronze Ding in Yin Ruins.     

Corrosion and electrochemical behavior of Mg–Y alloys in 3.5% NaCl solution

The corrosion mechanism of Mg–Y alloys in 3.5% NaCl solution was investigated by electrochemical testing and SEM observation. The electrochemical results indicated that the corrosion potential of Mg–Y alloys in 3.5% NaCl solution increased with the increase of Y addition. The corrosion rate increased with the increase of Y addition because of the increase of Mg₂₄Y₅ intermetallic amounts. The corrosion gradually deteriorated with the increase of immersion time. The corrosion morphologies of the alloys were general corrosion for Mg–0.25Y and pitting corrosion for Mg–8Y and Mg–15Y, respectively. The main solid corrosion products were Mg(OH)₂ and Mg₂(OH)₃C1.4H₂O.     

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.