Corrosion-induced copper runoff from naturally and pre-patinated copper in a marine environment

Corrosion-induced copper runoff has been monitored for copper sheet, naturally patinated copper and pre-patinated copper, with and without surface treatments, in a marine environment during one year. The study comprises solution measurements on total copper runoff rates, sulphates and chlorides released from the patina, and parallel surface analytical studies on patina formation, combined with electrochemical impedance measurements on changes in barrier properties during exposure. Bioassay tests and model predictions were applied to elucidate copper bioavailability at the immediate release situation. The runoff rate of copper was significantly lower compared to the corrosion rate throughout the exposure period. At comparable rain quantities, copper runoff rates were significantly lower at the marine site compared to similar data obtained in an urban environment. The bioavailable concentration of released copper was significantly lower compared to the total copper concentration.     

A study of copper runoff in an urban atmosphere

Initiated by the concern in several countries regarding the release of copper from, e.g., roofs, facings and other outdoor constructions, the present study aims to compare runoff rates with corrosion rates during exposure of copper in an urban atmosphere. The copper runoff rate turns out to be relatively stable during the 2 year period studied, with an average rate per year of around 135 μg Cu cm⁻². This stable runoff rate is associated with the formation and dissolution properties of cuprite (Cu₂O), which is the dominating copper patina phase throughout the 2 year period. The copper corrosion rate, on the other hand, is highly time-dependent. It exhibits an initially high value and decreases with exposure time. As a consequence, the ratio between copper runoff and copper mass loss is very low in the beginning, around 7% after 1 month, and increases with time to reach around 22% after 2 years. With prolonged exposure this ratio eventually reaches 100%, corresponding to a copper patina thickness that does not change any further with time.     

A field study on the first flush effect of copper roof runoff

The runoff of four copper roof surfaces with different aspects were monitored in a field study in order to identify the existence of the first flush effect and to determine the influences. It was found that almost 40% of all sampled precipitation events exhibited a moderate first flush effect regarding the distribution of copper mass in the roof runoff. There was a significant impact of the roof aspect on the presence and on the magnitude of the first flush. No correlation was found between the first flush effect and weather parameters, such as rain height, rain intensity, and antecedent dry weather period.     

The atmospheric corrosion of quaternary bronzes: The leaching action of acid rain

The effect of leaching rain on the corrosion behaviour of bronze UNSC83600 was investigated as to the influence of alloying elements (Cu, Sn, Zn, Pb) through dropping tests simulating a severe runoff condition with a solution reproducing natural acid rain. Corrosion was followed with time monitoring both samples and leaching solutions (up to 30 days) by SEM, EDS, Raman spectroscopy, XRD, AAS. The bronze patina behaves as a porous layer enriched in stable tin compounds allowing uniform dissolution of Cu, Zn and partly of Pb. Laboratory results are in good agreement with field studies of outdoor bronzes in unsheltered condition.     

The atmospheric corrosion of quaternary bronzes: The action of stagnant rain water

The corrosion behaviour of a quaternary bronze UNS C83600 exposed to stagnant acid rain was examined through wet-dry tests. During the tests, parallel monitoring was performed to determine the evolution of both the bronze surface and the weathering solution composition. The results show that the kinetics of bronze oxidation is governed by diffusion through a two-layer patina: an inner Sn-rich layer and an external Cu and Pb-rich layer. The corrosion rate of the alloy decreases with time, but the dissolution of individual metals (Cu, Zn and Pb) in the environment increases with different trends, showing progressive patina destabilisation.     

Atmospheric corrosion of copper and the colour, structure and composition of natural patinas on copper

This paper describes the results of atmospheric corrosion testing and of an examination of patina samples from Brisbane, Denmark, Sweden, France, USA and Austria. The aim was threefold: (1) to determine the structure of natural patinas and to relate their structure to their appearance in service and to the atmospheric corrosion of copper; (2) to understand why a brown rust coloured layer forms on the surface of some copper patinas; (3) to understand why some patinas are still black in colour despite being of significant age. During the atmospheric corrosion of copper, a two-layer patina forms on the copper surface. Cuprite is the initial corrosion product and cuprite is always the patina layer in contact with the copper. The growth laws describing patina formation indicate that the decreasing corrosion rate with increasing exposure time is due to the protective nature of the cuprite layer. The green patinas were typically characterised by an outer layer of brochantite, which forms as individual crystals on the surface of the cuprite layer, probably by a precipitation reaction from an aqueous surface layer on the cuprite layer. Natural patinas come in a variety of colours. The colour is controlled by the amount of the patina and its chemical composition. Thin patinas containing predominantly cuprite were black. If the patina was sufficiently thick, and the [Fe]/[Cu] ratio was low, then the patina was green, whereas if the [Fe]/[Cu] ratio was approximately 10 at%, then the patina is rust brown in colour. The iron was in solid solution in the brochantite, which might be designated as a (copper/iron) hydroxysulphate. In the brown patinas examined, the iron was distributed predominately in the outermost part of the patina.     

Time focused measurements of roof runoff quality

Runoff properties and their changes during runoff of a 14 year old zinc roof were investigated. Zinc, lead, cadmium, pH value, rain intensity and electric conductivity have been measured for a period of one year. A runoff rate of 3.73 g/m² a and a volume weighted mean zinc concentration of 4.9 mg/L were determined. First flush behaviour was observed in 93% of runoff events. Low rain intensities are correlating with higher zinc concentrations in runoff, whereas the duration of antecedent dry periods could not directly be linked with initial zinc concentrations.     

A3钢在模拟降雨环境下的腐蚀和冲刷行为研究

利用自制的实验室降雨模拟装置，研究了雨水pH值和降雨强度对A3钢的腐蚀和冲刷行为影响，同时用ACM（atmospheric corrosion montior)监测了降雨期间的腐蚀速率变化。结果表明，A3钢的腐蚀速率随着模拟雨水pH值的升高而降低，其变化规律与失重结果一致。表明用ACM监测A3钢在降雨条件下的腐蚀速率在一定程度上是可行的。A3钢的冲刷量随着模拟雨水pH值的升高表现为先降后升的规律，从腐蚀产的的变化分析了其产生的原因。随着模拟降雨强度的增大，A3钢的腐蚀速率和冲刷量增大，等量模拟降雨条件下，冲刷量与随降雨强度的增大而增大，这表明降雨的冲击作用对A3钢的腐蚀和冲刷行为有显著影响。     

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⁺.     

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.     

Early stages of copper corrosion behaviour in a Tunisian soil

The early stages of copper corrosion in a Tunisian soil were studied using mass loss, surface analysis (optical microscopy, visible spectroscopy, IRTF and atomic force microscopy) and electrochemical characterizations (polarization curves and cyclic voltammetry). The corrosion rate dependence with immersion time was Δm = at^b. Two behaviours for the material surface were evidenced when varying the soil concentration and temperature. Then, the apparent kinetic constant, the soil reaction order and the apparent activation energy were calculated. Analytical and electrochemical characterizations showed that a rough patina layer was build up as a result of the interaction between soil and copper.     

Zinc runoff from galvanised steel materials exposed in industrial/marine environment

Abstract

An investigation has been carried out to assess the zinc runoff from a variety of galvanised materials over 16 months at the industrial/marine Port Talbot weathering site. Over 16 months of exposure, bare zinc, and Electrozinc have the highest levels of zinc runoff (4·38 and 4·20 g m^-2) followed by general galvanised steel substrates, i.e. hot dip galvanised (HDG) steel (0·15 wt-%Al) (2·87 g m^-2) and iron zinc intermetallic galvanised steel (galvanneal, 2·36 g m^-2). Galvanneal (IZ) has a higher initial runoff rate than HDG due to the presence of iron/zinc intermetallic in the coating that promotes anodic zinc dissolution. The HDG has a more constant runoff rate that exceeds IZ after 7-8 months due to build up of corrosion products on the IZ surface. Aluminium/zinc alloy coated steels have a much lower runoff rate than general galvanised materials as the aluminium present in the structure provides a strongly protective oxide barrier coating improving corrosion resistance (Galfan 5 wt-%Al, 2·04 g m^-2, and Z alutite 55 wt-%Al, 0·67 g m^-2). Organically coated steels show relatively little zinc runoff (< 0·25 g m^-2) indicating their effectiveness in preventing surface corrosion. Runoff levels measured do not exceed permissible levels of zinc for drinking water and the measured zinc runoff levels pose little threat to organisms if leached into soil. Using an accelerated laboratory test in which distilled water is sprayed onto specimen panels in a recirculatory system for 100 h a good correlation can be obtained with external exposure for up to 6 months exposure. For 12 months exposure iron zinc intermetallic galvanising (galvanneal) begins to become covered in a protective oxide layer, which cannot form under the conditions of the accelerated test. Despite this, the fit for most specimen types is excellent. Where the predictive test fails is when the galvanising layer is breached revealing an efficient iron cathode site. This occurs first for electrocoated zinc after 16 months exposure. Similar predictive results can be obtained using a scanning vibrating electrode technique (SVET) in a semiquantitative manner and an immersion electrolyte of 0·1 wt-%NaCl. Again the predictions are initially very accurate but following 12 months exposure the fit for specimens of electrozinc is poor due to the breaching of the galvanising layer.     

沈阳大气环境下纯铜的初期腐蚀行为

通过1年的遮雨和未遮雨大气暴露实验,研究了在沈阳大气环境下纯铜的初期腐蚀行为.不同暴露环境下,纯铜的大气腐蚀速率、腐蚀产物组成及其保护性都存在差异.未遮雨暴露条件下,纯铜的大气腐蚀速率较高,尤其在降雨较多的暴露期间,雨水冲刷使纯铜经历了更长的润湿周期,从而显著加速了纯铜的大气腐蚀.不同暴露条件下,纯铜表面形成的大气腐蚀产物主要为Cu2O.遮雨条件下,腐蚀产物的组成还有Cu4SO4(OH)6·H2O和Cu4SO4(OH)6;而未遮雨条件下,雨水的冲刷、溶解作用延缓了Cu4SO4(OH)6·H2O的形成,因而在6个月时腐蚀产物仅为Cu2O;随着暴露周期的延长,12个月后逐渐有Cu4SO4(OH)6·H2O形成.未遮雨暴露的纯铜表面形成了致密的厚腐蚀产物膜,有效地抑制了大气腐蚀的阴极反应,具有更好的保护性.     

Applicability of constant dew point corrosion tests for evaluating atmospheric corrosion of aluminium alloys

Field exposure tests of aluminium alloys were conducted at three sites in Japan. Meteorological data indicated that the dew point of the ambient atmosphere and aluminium panels remained constant for the short-term. Constant dew point corrosion tests were employed to reproduce atmospheric corrosion of aluminium alloys in the laboratory. The corrosion rates, corrosion morphology and corrosion product composition after 7 days of tests in the laboratory were similar to those formed after 3 months of exposure at coastal sites. Not only did the constant dew point corrosion test effectively reproduce the atmospheric corrosion of aluminium alloys, it also accelerated it.     

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.     

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.     

Inhibition of copper corrosion by isatin in aerated 0.5 M H2SO4

The corrosion inhibition of commercial copper by means of isatin was studied in aerated 0.5 M H₂SO₄ in the temperature range 25-55 °C using weight-loss, potentiodynamic and spectrophotometric tests, and determination of double layer capacitance. Inhibition efficiencies up to 94% in the concentration range of 1×10⁻⁴-7.5×10⁻³ M of isatin were obtained. The corrosion rates estimated with weight-loss measurements were higher than those correspondingly determined with the potentiodynamic test, especially at higher concentrations of inhibitor. This is in accord with other researches that have pointed out the limitation of the Tafel line extrapolation method in the determination of corrosion rates. The kinetics of cuprous and cupric ion formation and UV-visible spectra support the formation hypothesis of a complex between copper and isatin. The adsorptive behaviour of isatin on copper 0.5 M H₂SO₄ was also investigated.     

Long term corrosion behaviour of copper in soil: A study of archaeological analogues

The long term corrosion behaviour of copper in soil environment has been addressed by studying two archaeological copper samples. The microstructures of the material of construction of a Chalcolithic (2350BC‐1800BC) copper chisel from Balathal and an OCP period (2650BC‐800BC) Cu anthropomorphic object have been first characterized by microscopy and the features understood by stereological methods. The equiaxed grain size, coring effects in the grains and the relatively soft matrix of the OCP copper object indicated that it was manufactured by casting. The deformed grains near the surfaces and variation in the microhardness of the sample at different points suggests that the Chalcolithic copper chisel was processed by cold deformation after casting of the square cross section chisel. The surface patina on the two archaelogical copper objects has been characterized by X‐ray diffraction. In the case of OCP copper, the green surface patina was analyzed as a mixture composed mainly of cuprite, and minor amounts of malachite and brochantite. In the case of Chalcolithic copper, the patina was composed of sulfates and oxysulfates in the outer layers while the inner layers were rich in copper oxides. The electrochemical behaviour of both the archaeololgical coppers has been characterized and compared with that of a modern Cu sample by potentiodynamic polarization studies. The corrosion rate, determined by Tafel extrapolation technique in 3.5% NaCl solution, of Chalcolithic Cu was only marginally higher than that of modern and OCP Cu. The higher rates of corrosion in case of archaeological coppers have been attributed to the presence of second phase sulfide inclusions.     

Weight loss studies of fastener materials corrosion in contact with timbers treated with copper azole and alkaline copper quaternary compounds

Corrosion rates of mild steel, AISI 316 stainless steel and hot-dipped galvanised steel in contact with preservative-treated Pinus radiata have been determined using four distinct accelerated (49 ± 1 °C) and non-accelerated (21 ± 2 °C) weight loss methodologies. The data were measured as a function of timber moisture content and copper concentration over periods of exposure ranging from 2 weeks to 14 months. The results show that the corrosion resistance of the stainless steel was not influenced by classification or magnitude of preservative loading. Corrosion rates of this material were multiple orders of magnitude lower than those of the mild and galvanised steels. In most instances, corrosion rates of hot-dipped galvanised layers in contact with alkaline copper quaternary-treated timbers were up to a factor of 10 times, or greater, than those measured for copper-chrome-arsenate treatments. A direct negative influence of copper ion concentration on the corrosion resistance of mild steel was also observed for each preservative type.     

The pitting corrosion of copper tubes in hot water

The electrode potential of copper tube used in hot water distribution system in buildings rises gradually with time of exposure and then attains to a critical value of pitting potential after a long incubation period. The process of potential rise proceeds in two stages. The first stage is the formation of a cuprous oxide layer in the potential range ≦ 60 mV(SCE) and the second stage is due to the reactions of chlorite ions accumulated in the cuprous oxide layer in the potential range > 60 mV(SCE). Oxyacids and oxyanions of chlorine formed in the water, to which chlorine gas or hypochlorite was added for sterilizing process, accelerate the formation of cuprous oxide layer in the first stage, and the reaction of chlorite ions increase the electrode potential of copper tube in the second stage.