Effect of passive film on the galvanic corrosion of titanium alloy Ti60 coupled to copper alloy H62

Ti alloys exhibit high potential because of the compact passive film. However, the effect of passive film on galvanic corrosion is not clear. On the one hand, the great potential difference can accelerate the galvanic corrosion of other metals with low potential. On the other hand, the passive film can hinder the electrochemical reactions, inhibiting the galvanic corrosion. To clarify this question, the galvanic corrosion of titanium alloy Ti60 coupled to copper alloy H62 was studied using zero‐resistance ammeter, scanning vibrating electrode technique, scanning electron microscopy, and potentiodynamic polarization measurements. The chemical composition and electrical properties of the passive film on Ti60 were detected using X‐ray photoelectron spectroscopy and Mott‐Schottky plots. The results indicate the galvanic corrosion of Ti60‐H62 coupling is ignorable in spite of the great galvanic potential difference between them. It can be attributed to the low electron donor density of passive film, which inhibits the electron charge transfer process at the film/solution interface, causing the slow cathodic reaction rate on Ti60.     

铜在含SO2大气中的腐蚀初期规律和机理

利用原子力显微镜 (AFM)原位考察了铜在SO2 质量分数为 0 .9× 1 0 - 6和 90 %相对湿度条件下 ,大气腐蚀过程中表面形貌及结构变化 ,观察到铜在大气腐蚀中高分辨的形貌变化过程 :铜表面逐渐形成纳米级的蚀点 ,并随着时间延长变大和彼此交迭 ,而后开始更大尺度的新一层次蚀点的发展 ,表现出腐蚀微电池层次发展特征。红外反射吸收光谱 (IRAS)表明 ,碱式硫酸盐是构成腐蚀产物膜的主要组分。石英晶体微天平 (QCM)原位测得的动力学曲线表明 ,铜在该条件下的腐蚀速度呈现出随时间延长而逐渐下降的趋势 ,说明形成的腐蚀产物对进一步腐蚀产生抑制作用。     

不同腐蚀介质中16Mn钢高温高压腐蚀行为的比较

采用高压釜研究了16Mn钢在含有CO2与CO2+H2S介质的NACE(5wt%NaCl+0.5wt%CH3COOH)溶液中的高温高压腐蚀行为,利用失重法计算了腐蚀速率,通过SEM,XRD,EPMA等手段分析了腐蚀产物的成分及结构。结果表明:CO2腐蚀产物主要为Fe3C;CO2+H2S腐蚀产物主要为FeS,60℃时有FeCO3形成,腐蚀主要显示以CO2腐蚀为主的点蚀特征,90~120℃时,腐蚀系统以H2S腐蚀为主导,腐蚀产生的鼓泡、阶梯状裂纹是CO2与H2S协同作用的结果,CO2会增大H2S腐蚀的敏感性,使腐蚀产生氢损伤的温度提高。     

Cu-Al-Mn合金脱合金腐蚀现象的研究

采用电子探针技术研究了Cu-Al-Mn合金脱合金腐蚀现象及其产物，结果表明．Cu-Al-Mn合金中亚稳β相含销量较高．优先发生脱铝腐蚀．并沿着亚稳β相不断扩展，待亚稳β相完全被腐蚀后，腐蚀向α相扩展．腐蚀产物中含有铝元素、氯元素及氧元素。腐蚀初期．因亚稳β相脱铝而使该区成为贫铝富铜区；腐蚀后期，亚稳β相被完全腐蚀而使该区成为富销的产物区。     

Effect of temperature on copper corrosion in high-level nuclear waste environment

The effect of temperature on the corrosion behavior of copper in simulated high-level nuclear waste environment was systematically studied. Electrochemical methods, including electrochemical impendence spectra, Mott–Schottky technology, cyclic polarization, and potentiostatic polarization, were employed to characterize the corrosion behavior of copper at different temperatures. Stereoscopic microscopy and scanning electron microscopy were used to examine the surface morphology, and X-ray photoelectron spectroscopy analysis was used to identify the composition of the passive film. The experimental results show that corrosion resistance of the passive film does not blindly decrease with the increase of temperature but increases at 60 °C owing to a compact outer layer; there is a potential for pitting corrosion, which decreases as the temperature increases. The main product of copper in an anaerobic aqueous sulfide solution is Cu₂S but the content of CuS increases at higher temperatures. The whole passivation range shows p-type semiconductor characteristics and the magnitude of the acceptor density is 10²³ cm^?3, which increases with increasing temperature.     

The effect of solution temperature and pH on corrosion performance and morphology of nanoceramic‐based conversion thin film

In the present study, a nanoceramic hexafluorozirconic acid was used as an eco‐friendly conversion coating, which is free of the conventional phosphate salts. The effect of practical parameters on morphology and corrosion resistance of the coating was studied. Anti‐corrosion behavior of the nanoceramic‐based conversion coating on cold rolled steel substrates was evaluated at different solution pH and temperatures, utilizing the electrochemical impedance spectroscopy and direct current polarization. Moreover, the morphology of thin films was studied using field emission scanning electron microscopy (FE‐SEM). The results revealed that the conversion thin films formed at a dipping temperature of 20 °C and pH 4.5 showed best anti‐corrosion performance. SEM images indicated that increasing solution temperature resulted in micro‐cracks creation and lack of consistency on the surface of the conversion coating. Moreover, the morphological structure changed with increasing pH value.     

高含H2S/CO2环境中套管钢腐蚀行为与腐蚀产物膜关系

研究了在高含H1S/CO2环境中腐蚀产物膜在套管钢腐蚀过程中作用.通过模拟某气田井下腐蚀环境,采用失重腐蚀方法研究了NT80ss和L80钢钢在1.5MPu、30～120℃环境中腐蚀规律,并采用电化学交流阻抗(EIS)技术和扫描电镜(SEM)分析了腐蚀产物膜和腐蚀行为的关系.结果表明:60℃为NT80ss和L80钢腐蚀的临界温度,低于60℃时.随温度增加,腐蚀速率降低,高于60℃时,腐蚀速率随温度增加而增大;与其它温度相比,在60℃环境中NT80ss和L80钢腐蚀产物膜的阻抗能力最强、膜的致密性最好,相应腐蚀速率最低.     

Inhibition of copper corrosion by modifying cysteine self‐assembled film with alkylamine/alkylacid compounds

Complex self‐assembled monolayers (SAMs) were prepared by modifying the adsorption of cysteine with dodecylacid (DAC) and with dodecylamine (DAM) on copper surfaces. Their protective effects against copper corrosion were investigated by potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) in 0.5 M HCl aqueous solution. Results show that SAMs suppress cathodic current densities and shift the corrosion potential toward more negative values. Two types of complex SAMs enhance the anticorrosion effect of cysteine SAMs. PM3 semi‐empirical quantum calculations were used to obtain the quantum chemical parameters. The complex SAMs formed from cysteine and DAM have the higher E_HOMO level and the better protection effect.     

An investigation on the mechanisms of ant nest corrosion of copper tube in formic acid environment

Copper tubes used in air-conditioners and refrigerators often fail due to ant nest corrosion (ANC) in formic acid environment. In this paper, corrosion behavior and corrosion mechanisms of copper tubes in formic acid (HCOOH) were analyzed by vapor corrosion tests, optical microscopy (OM), scanning electron microscope (SEM), energy-dispersive X-ray spectrometry (EDS). The effects of the surface condition on ANC of copper tube were also investigated. Results showed that ANC of copper tube was a spontaneous process. The surface integrity of copper tube surface oxide layer is not the decisive factor of ANC. ANC originated from the dissolution of the surface oxide layer in HCOOH, which exposed fresh copper matrix. ANC is a special electrochemical corrosion, where the copper matrix acts as an anode and the undissolved surface oxide layer acts as a cathode due to the potential difference. The accumulation of corrosion products consisting of Cu(HCOO)₂ and Cu₂O can produce a wedge effect and generate many microcracks until to penetrate the copper tube wall. These findings would provide a deep understanding of the corrosion behavior of copper and copper alloys.     

镍对铜/不锈钢GTAW接头导电性及腐蚀性能的影响

针对新型铜/不锈钢单缝直焊型电解铜永久阴极板焊接接头的特殊要求,采用S201,S231和CuNi-7三种不同Ni含量的焊丝对T2紫铜与316L不锈钢进行GTAW焊,并对接头微观组织、成分、电导率和耐腐蚀性进行了分析.结果表明,三种不同Ni含量的焊丝所得焊缝界面清晰、无明显的宏观焊缝缺陷,但Ni含量的增加会对焊缝表面成形有一定影响;Ni含量低时会使钢侧焊缝中产生少量微裂纹,而随着Ni含量的增加焊缝中条状和块状Ni-Cr-Fe相随之增加;随着焊缝中Ni含量的增加,铜/不锈钢接头的电导率有所下降,这与焊缝中存在的Ni-Cr-Fe相数量成反比;铜/钢接头中Ni含量的增加可较为明显地提高铜/钢接头在酸性条件下的耐腐蚀性能.     

用球差校正扫描透射电镜研究人工时效7075铝合金的耐蚀性（英文）

使用先进的球差校正扫描透射电子显微镜研究人工时效7075铝合金耐腐蚀性增强机制。通过阻抗谱、等效电路分析、极化测量和浸泡试验,研究人工时效7075铝合金在3.5%(质量分数) NaCl溶液中的腐蚀行为。结果表明,人工时效时间越长,7075铝合金的耐腐蚀性越好。这可能归因于扫描透射电镜技术揭示的以下显微组织特征：在过时效条件下,晶界处的铜偏析有助于延缓晶间腐蚀,在Al₁₈Mg₃(Cr,Mn)₂分散体表面形成的Mg(Zn,Cu)₂沉淀有效地将作为腐蚀阴极的分散体与铝基体隔离。这项研究证明,可以通过适当的合金化和人工时效来设计耐腐蚀合金的可能性。     

Characterisation of corrosion products formed on copper exposed at indoor and outdoor sites with high H2S concentrations

Abstract

Corrosion products formed on copper exposed indoors and outdoors at sites with high hydrogen sulphide (H₂S) concentrations were characterised using several analytical techniques. The crystalline corrosion products that formed on the copper exposed indoors were chalcocite (Cu₂S) and cuprite (Cu₂O), while those that formed on the copper exposed outdoors were chalcocite, cuprite and basic copper sulphates. Surface analysis by X-ray photoelectron spectroscopy revealed differences between the copper exposed indoors and outdoors that are explained by the composition, localisation and oxidation of the corrosion products. The surface morphologies of the corrosion products also differed. Elemental depth profiling by glow discharge optical emission spectroscopy revealed that the corrosion products that formed indoors were mainly chalcocite with cuprite only at and near the surface. In contrast, the corrosion products that formed outdoors were a mixture of chalcocite and cuprite. These differences in corrosion products are attributed to the differences in relative humidity during exposure.     

Effect of surface oxide properties on corrosion resistance of 316L stainless steel for biomedical applications

Surface passivation is a promising technique for improving the corrosion resistance both in vitro and in vivo as well as the biocompatibility of 316L stainless steel. In this work, we studied the effect of different passivative processes on the in vitro corrosion resistance of 316L stainless steel wire. Characterization techniques such as anodic polarization test, scanning electron microscopy, auger electron spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy were employed to co-relate the corrosion behavior to various surface characteristics and surface treatments. Results showed that all of these surface treatments did not improve the corrosion resistance of the alloy satisfactorily except amorphous oxidation. This improvement is attributed to the removal of plastically deformed native air-formed oxide layer and the replacement of a newly grown, more uniform and compact one which is composed of nano-scale oxide particles with higher oxygen and chromium concentrations. The properties of surface oxide layer, rather than its thickness, seem to be the predominant factor to explain the improvement of in vitro corrosion resistance.     

Further results on the in situ anaerobic corrosion of carbon steel and copper in compacted bentonite exposed to natural Opalinus Clay porewater containing native microbial populations

Since 2012, a long-term in situ corrosion experiment (IC-A) is being conducted in the Mont Terri Underground Research Laboratory in Switzerland to investigate the corrosion behaviour of candidate canister materials in conditions representative of the Swiss concept for the disposal of high-level waste and spent nuclear fuel. To date, carbon steel and various types of copper coatings have been retrieved after different exposure periods of up to 3 years, and characterised to establish the composition of the corrosion product, the morphology of the corroded surface, the nature of the interaction between the metal and the surrounding bentonite, and the microbial populations in the bentonite and surrounding porewater. For carbon steel specimens, a complex corrosion product was identified, consisting predominantly of magnetite. Much less alteration on either the metal or the bentonite was observed in the case of copper samples. Low average anaerobic corrosion rates were measured for carbon steel and a very modest amount of alteration was identified on copper. The density and the initial form of the bentonite had a small influence on the rate of corrosion, across all materials. This paper summarises the results of the experimental programme obtained to date and discusses the relationship observed between exposure time and the evolution of the metal–bentonite interface for both carbon steel and copper.     

煤气管道用耐酸钢硫酸腐蚀行为研究

高炉煤气输送管道通常采用普碳钢,而煤气管道中含有硫酸、硝酸和氯离子等多种腐蚀性介质,对管道造成腐蚀,管道使用寿命低。针对研发的煤气管道用耐酸钢,采用均匀腐蚀全浸试验对其硫酸腐蚀行为进行了研究,利用扫描电镜(SEM)、电子探针(EPMA)、激光共焦扫描显微镜(LSCM)等手段揭示其腐蚀行为。结果表明,煤气管道用耐酸钢有优异的耐硫酸腐蚀性能;Cu、Sb、Cr等耐腐蚀元素的加入有利于改善点蚀现象,并在耐酸钢表面形成一层致密的不溶于硫酸的富含Cu、Sb、Cr等元素的钝化膜,从而增强耐酸钢的耐硫酸腐蚀性能;适量的S元素含量有利于提高钢的耐硫酸腐蚀性能。     

Structure and properties of brazed joints on dispersion-strengthened copper

Development of the technological process for brazing of heat-resistant copper alloy strengthened with Al2O3 oxide particles is an important task of fabrication of high-temperature application structures. As mechanical properties of the brazed joints directly depend on the structural factor and morphological peculiarities of the brazed seams, the latter are of technological interest in terms of making of permanent joints. This study gives results of X-ray spectral microanalysis of the brazed joints on dispersion-strengthened copper alloy （ Gridcop Al-25 ） produced by using the Ti-Cu system adhesion-active brazing filler alloy, different heat sources and temperature-time parameters of the brazing process. Shown are differences in formation of structure of the seams made by vacuum brazing using radiation and high-frequency heating. Vacuum brazing with radiation heating provides the homogeneous seams with crystallisation of the phases based on the CuTi and CuTi2 compounds in the form of discrete faceted particles 2 - 9μm in size against the background of the copper matrix. Based on investigation of structural peculiarities of the brazed seams, the temperature-time conditions of vacuum brazing with radiation heating were selected for manufacture of specimens for mechanical tests. Analysis of the results of strength tests of the butt brazed specimens proved the expediency of preliminary heat treatment of the base material, providing strength of the joints at a level of about 92% of that of the base material.     

时效时间和Cu含量对Ni-Ti-Cu形状记忆合金耐蚀性的影响

通过改变Ni-Ti-Cu形状记忆合金(SMA)中Cu的含量,并在450℃进行不同时间的时效处理,用X射线衍射分析(XRD)、动电位扫描技术、扫描电子显微镜(SEM)观察及能谱分析(EDS)研究了时效Ni-Ti-Cu形状记忆合金在生理盐水中的耐蚀性,并与经相同处理的Ni-Ti二元合金腐蚀情况进行对比。结果表明,时效时间的延长会使Ni-Ti合金及含3at%Cu的Ni-Ti-Cu合金抗蚀性降低;对含6at%Cu的Ni-Ti-Cu合金,随时效时间的延长耐蚀性有一定的提高;以Cu代替Ni-Ti合金中部分的Ni会使得合金在生理盐水中的耐蚀性比Ni-Ti二元合金差。