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.     

紫铜海水管焊接部位在海水中的腐蚀特征

采用金相显微镜、X射线衍射仪、扫描电镜结合能谱测试技术研究了紫铜海水管焊接接头部位在海水中的腐蚀特征。结果表明:采用黄铜焊条的接头部位为α β双相黄铜,在海水中发生了严重的不均匀脱锌腐蚀,脱锌后合金表面的颜色由黄变为紫红;腐蚀产物主要由ZnCl2和ZnSO4等锌盐和锌的氧化物ZnO2和ZnO组成,此外还含有少量的铜绿Cu3(SO4)(OH)4;采用白铜焊条的接头部位为Cu-Ni-Zn三元单相固溶体(α相),在海水中浸泡前后结构未发生变化,表面较致密、无明显孔洞和点蚀,与黄铜焊缝相比,具有优异的耐海水腐蚀性能。     

Corrosion of vertical mild steel strips in seawater

This paper describes the corrosion loss profiles of 1 m long vertical steel strips attached to a raft and exposed for 1 year in calm natural seawater on the Australian eastern seaboard. The upper parts of the strips were exposed to the atmosphere and the lower parts immersed to depths varying from 0.3 to 0.9 m. It was found that, irrespective of the precise ratio of atmospheric/immersion exposure, corrosion in the splash zone was much higher than that at the waterline and in the atmosphere. There was also significant corrosion in the immersion zone, immediately below the waterline, consistent with classical observations. Above the water line there was only moderate variability in corrosion between the strips but there was much greater variability in corrosion loss for the parts of the strips fully immersed. Mass loss observations are compared with observations of the corrosion and pitting patterns observed in the various zones. Potential reasons for these observations are considered. The observations have implications for explaining aspects of accelerated low water corrosion (ALWC).     

铜合金及其复合材料在氯化钠盐雾中的腐蚀行为

通过氯化钠盐雾腐蚀实验,结合X射线衍射(XRD)和电子探针(EPMA)分析,研究了铜合金及其复合材料在氯化钠盐雾中的腐蚀行为.结果表明:在实验初期材料的腐蚀速度随时间的延长而降低,约96 h以后腐蚀速度基本不再变化;BZn15-17与纯镍复合材料的耐蚀性最好;实验初期和后期的腐蚀产物组成基本相同,2种白铜合金的主要腐蚀产物都是CuCl2@2H2O,黄铜合金的主要腐蚀产物为CuCl,其次为CuCl2@2H2O和(CuZn)2(OH)3Cl;腐蚀形貌变化较大.     

Characteristics and formation of corrosion product films of 70Cu-30Ni alloy in seawater

The corrosion product films of 70Cu-30Ni alloy, composed of recrystallized grains or deformed and recrystallized grains, were investigated in 3.5% NaCl and natural seawater by electrochemical techniques, SEM, EDX and AES. The recrystallized alloy displayed a steady increase in the polarization resistance while the alloy of incomplete recrystallization kept its polarization resistance at a low level as increasing the immersion time in 3.5% NaCl. The films formed on the recrystallized alloy in seawater were thin, uniform and rich in nickel. After long-term immersion, the films, still thin and protective, consisted of convex lines and smooth zones between the lines. The convex lines were richer in nickel and contained more seawater species than the zones, so this led the lines to preferentially dissolve and new lines to appear where the film grew slower. Immersed in seawater, the alloy of incomplete recrystallization showed thick, loose and porous films, of which the inner layer was denickelified and the outer layer contained a great amount of seawater species, and of which the underlying substrate was found with severe intergranular corrosion. The tube specimens of incomplete recrystallization for four-year immersion were perforated by intergranular corrosion.     

Corrosion study of copper in the presence of benzotriazole and its hydroxy derivative

The inhibitory properties of benzotriazole (BTAH) and its hydroxy derivative, 1‐hydroxy‐benzotriazole (BTAOH) on copper corrosion, were compared in 3% NaCl solution using cyclic voltammetry (CV), immersion tests, profilometry and scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDX). CV experiments showed rapid interaction of both inhibitors with a Cu surface, but only at high concentrations. Immersion tests under stationary conditions showed that BTAOH offered corrosion protection only at concentration of 10 mM. Moreover, it was not effective under stirring conditions at any of the concentrations investigated. In contrast, BTAH exhibited good corrosion inhibition ability in all immersion tests. BTAOH, at up to 1 mM, increased the surface roughness of Cu more than 3% NaCl solution alone, but a significant reduction of surface roughening was observed when BTAH was present. Porous cross‐linked acicular structures and star‐like structures were observed using SEM/EDX in the case of BTAOH treatment. When Cu was treated with BTAH, roundish surface structures composed of bent plates with toothed‐like edges, acicular structures and non‐porous few hundred nm thick plates were observed.     

Corrosion characteristics of copper in magnetized sea water

The corrosion characteristics of copper in magnetic action system were investigated by mass loss method, electrochemical test, scanning electron microscopy （SEM） and energy analysis. It is found that the corrosion process of copper is influenced by magnetic field. The flow corrosion rate of copper decreases at the initial segment, then drives to gentle stage at the final segment. From electrochemical test, the corrosion rate of copper in the magnetized sea water is minimal compared with that in 3.5% NaCl solution and sea water. Electlochemical impedance spectroscopy （EIS） plots of copper in 3.5% NaCl, sea water and magnetized sea water are similar. However, EIS plot of copper in magnetized sea water shifts rightwards due to the effect of magnetic field on sea water. The corrosion process of copper in magnetized sea water is pitting corrosion. The surfaces of samples are finer in magnetized sea water relative to those in 3.5% NaCl solution and sea water. The corrosion products of copper include large amount of Cu element, O element and Cl element. Cu2O and CuCl2 are the primary products. This suggests that electromagnetic treatment has remarkable effect on the corrosion of copper.     

Localized corrosion of copper alloys in China seawater for 16 years

The regulation of localized corrosion of 2 kinds of copper and 17 kinds of copper alloys exposed in seawater of Qingdao, Zhoushan, Yulin and Xiamen for 16 years has been studied. Results show that during immersion copper alloys suffer from pitting corrosion due to high temperature and marine living adhesion at Yulin, and to the higher velocity of seawater containing sand at Zhoushan. However, the seawater of Xiamen inhibits the pitting corrosion of copper alloys. No pitting corrosion is observed on copper alloy plates tested there. The copper alloys suffer from more serious pitting corrosion in the tide zone than that in the immersion zone at Qingdao after long time exposure.     

Field studies of corrosion behaviour of copper alloys in natural seawater

Eight copper alloys were tested in a one-year field deployment in the North Atlantic Ocean. The corrosion behaviour was characterized by weight loss, optical and electronic microscopy analyses. The biofouling performance was quantified in terms of the biomass accumulation. The testing program included specimens in tensioned and untensioned configurations, as well as a set for seasonal deployments. The seasonal corrosion rates were 140% higher, and the rates of tensioned specimens were 39% higher than those of the untensioned specimens after 12 months of deployment. Good biofouling resistance was observed for all but one alloy, which exhibited heavy fouling by barnacles.     

Indoor atmospheric corrosion of copper and steel under heat trap conditions in Cuban tropical climate

Abstract

Corrosion behaviour of copper and steel under heat trap conditions in Cuban tropical climate is reported. Temperature and humidity reach higher values than those reported for traditional outdoor and indoor conditions. Annual calculated time of wetness is in the range corresponding to outdoor or ventilated sheds. This behaviour is not reported for other indoor conditions. Sulphur compounds deposition rate is higher than chloride deposition rate at all corrosion stations. Main corrosion products formed on steel and copper are goethite and brochantite respectively. No significant differences in the statistical influence of exposure time and time of wetness on atmospheric corrosion process of copper and steel under heat trap conditions are determined.     

旋转磁场对海水中铜流动腐蚀的影响(英文)

通过实验室中12d的旋转电磁腐蚀实验,研究海水中铜的流动腐蚀。利用扫描电镜和X射线能量分散分析系统(SEM/EDAX)和X射线衍射仪(XRD)分析铜试样的表面微观结构和相组成,包括空干后腐蚀产物膜中的Cu2O和CuO的组成。结果表明:流动腐蚀过程是坑蚀、扩展、腐蚀产物膜和表面产物溶液,最后是坑蚀。旋转电磁场抑制了铜在海水中的流动腐蚀。     

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.     

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⁺.     

Early corrosion of mild steel in seawater

Because field studies seldom recover coupons less than 6 months from immersion they provide no information about early corrosion behaviour. Linear or power law functional behaviour for corrosion loss with time is often assumed. New field studies performed on the Australian east coast and described herein using very closely spaced recoveries of coupons show that the corrosion loss-time behaviour is initially highly non-linear and then almost linear until corrosion product formation begins to control the rate of corrosion. The reasons for this behaviour are discussed in terms of the recently introduced multi-phase phenomenological model for marine corrosion. Conventional oxygen diffusion arguments are then used to provide a mathematical model to describe the main part of this behaviour. The possible influences of seawater temperature and oxygen concentration are discussed.     

常压储罐罐底腐蚀的漏磁检测与失效分析

探讨了漏磁检测在常压储罐罐底腐蚀缺陷检测中的应用。利用FLOORMAP 2000罐底漏磁扫描仪对五个1000m^3以上的常压储罐进行现场检测，给出了罐底的腐蚀状况。漏磁检测、宏观检测和超声波测厚结果的对比分析证实了漏磁检测方法的可靠性，最后综合分析了引起储罐罐底腐蚀失效的主要原因。     

Corrosion behaviour of copper under chloride-containing thin electrolyte layer

The corrosion behaviour of copper under chloride-containing thin electrolyte layers (TEL) was investigated using electrochemical impedance spectroscopy (EIS), cathodic polarization, linear polarization, SEM/EDS and XRD. The results indicate that the copper corrosion rate increases as TEL thickness decreases during the initial stages. After 192 h of immersion, the corrosion rate of copper under TEL in this order: 300 > 402 > 199 > bulk solution > 101 μm. The corrosion behaviour is uniform under TEL, and pitting is the primary corrosion type in the bulk solution. A corrosion model of the behaviour of copper under chloride-containing TEL is proposed.     

Corrosion Evolution of Steel Reinforced Concrete Under Simulated Tidal and Immersion Zones of Marine Environment

The corrosion evolution processes of steel reinforced concrete under simulated tidal and immersion zones of marine environment were investigated by using electrochemical measurements and corrosion morphology observations.The results indicate that the corrosion of rebar in concrete under both environments experiences the deterioration from passivation to pitting corrosion and then to general corrosion.Specially,the pitting plays the major role only in the early stage of corrosion,and the general corrosion replaces the dominate role of pitting during the long-term corrosion.In addition,both the pitting depth on local surface and the rust thickness on the overall surface of rebar in the tidal condition are larger than those in immersion condition,which is attributed to the faster corrosion rate in tidal zone caused by the concentrated chloride ions and sufficient oxygen supply.     

Corrosion of copper-coated used nuclear fuel containers due to oxygen trapped in a Canadian deep geological repository

The Nuclear Waste Management Organization is evaluating the safety and feasibility of the permanent disposal of used nuclear fuel in a deep geological repository. Their current design concept utilises copper-coated steel used fuel containers to isolate the waste from the environment. Immediately following repository closure, a finite quantity of O₂ will be trapped inside the repository and could cause some amount of oxic corrosion to the outer copper layer of the containers. On a per container basis, 13?mol of O₂ will be trapped in the repository rooms at the time of closure, based on reference design dimensions. This corresponds to a maximum depth of copper corrosion of 81?μm, assuming a uniform distribution. This work also considers the sensitivity of this oxic corrosion allowance to various hypothetical design changes to the repository that may occur before or during construction.