Inhibierung von wässerigen und alkoholisch wässerigen Wärmeträgern

Inhibition of aqueous and alcoholic-aqueous heat-carriers To examine the effect of corrosion inhibitors mainly ®Preventol CI-2 in aqueous and aqueous alcoholic heat transfer media gravimetric and electrochemical corrosion tests were carried out with the materials grey cast iron, unalloyed steel, copper, brass, lead-tin-solder, aluminium and aluminium alloys up to a temperature of 90°C. In the presence of the inhibitor Preventol CI-2 uniform layers from 10 to ? 50 nm thickness are found on the metal surfaces and the measured massloss (ASTM, EMPA) decreased decidedly. Local corrosion as occurs e.g. by insufficient concentration of inhibitors forming surface layers, was found in none of the cases. The electrochemical examinations confirm the results of the chemical tests and provide indications with regard to the effective mechanisms. The influence of temperature and flow rate on the protective efficiency of the inhibitor can be showed. It is possible to eliminate the risk of galvanic corrosion by contacting copper and aluminium. The cavitation corrosion of grey cast iron is also appreciably reduced. Preventol CI-2 is a broad spectrum inhibitor for aqueous and aqueous alcoholic heat transfer media.     

应用电化学方法原位研究薄液膜下青铜的大气腐蚀行为(英文)

采用阴极极化曲线、开路电位和电化学阻抗谱,监测青铜在不同薄液膜厚度下的大气腐蚀行为。阴极极化曲线结果表明,阴极极限电流密度随着液膜的减薄而增大。电化学阻抗谱结果表明,在腐蚀初期,腐蚀速率随着液膜的减薄而增加,这主要是由于腐蚀速率是由阴极过程控制的;随着时间的延长,腐蚀程度随着液膜厚度的变化从强到弱的趋势为:150μm,310μm,100μm,本体溶液,57μm。开路电位和电化学阻抗谱实验较好地再现了原位电化学腐蚀信息,且电化学结果与物理表征具有良好的一致性。     

非恒温电解液中AA5083Al-Mg合金阳极氧化膜的制备及其耐蚀性

采用硼酸-硫酸-草酸电解液在铝合金表面制备有序多孔层,研究阳极氧化过程中电流随时间的变化,分析界面反应并计算膜层的生长效率。采用扫描电子显微镜、交流阻抗和动电位极化曲线研究膜层的微结构及其在不同温度环境下的耐蚀性。结果表明：在氧化层界面双离子层浓度的增大有利于提高膜层的生长效率。所制备的阳极氧化膜厚度为8-9μm,孔径为10-14 nm,膜层的微观形貌受金属基体组织结构的影响较大。在沸水封闭后膜层为分层结构,表面呈细片状。氧化膜层封闭后能够明显降低试样的自腐蚀电流密度,且耐蚀性随着环境温度的升高而具有更好的稳定性。     

A study of the corrosion of aluminum alloy 2024-T3 under thin electrolyte layers

The corrosion of aluminum alloy 2024-T3 (AA2024-T3) under thin electrolyte layers was studied in 3.0 wt% sodium chloride solutions by cathodic polarization and electrochemical impedance spectroscopy (EIS) method. The cathodic polarization measurements show that, when the electrolyte layer is thicker than 200 μm, the oxygen reduction current is close to that of the bulk solution. But in the range of 200-100 μm, the oxygen reduction current is inversely proportional to the layer thickness, which shows that the oxygen diffusion through the electrolyte layer is the rate-determining step for the oxygen reduction process. In the range of 100 μm to about 58 μm, the oxygen reduction current is slightly decreased probably due to the formation of aluminum hydroxide or the change of the diffusion pattern from 2-dimensional diffusion to one-dimensional diffusion. The further decrease in electrolyte layer thickness increase the oxygen reduction current to some extent again, because the diffusion of oxygen plays more important role in thin electrolyte layers.The EIS measurements show that the corrosion is controlled by the cathodic oxygen reduction at the initial stage, showing the largest corrosion rate at the electrolyte layer thickness of 105 μm. But at the later stage of corrosion, the anodic process begin to affect the corrosion rates and the corrosion rates show a maximum at 170 μm, which may be the thickness where the corrosion changes from cathodic control to anodic control. The corrosion rate under the very thin electrolyte layer (62 μm in this study) is even smaller than that in bulk solution, this is due to that the anodic process is strongly inhibited.     

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.     

Characterisation of oxide films produced by plasma electrolytic oxidation of a Ti–6Al–4V alloy

The paper discusses processing and property aspects of oxide films formed on a Ti–6Al–4V alloy by AC plasma electrolytic oxidation (PEO) in aqueous solutions containing aluminate, phosphate, silicate and sulfate anions and some of their combinations. Structure, composition, mechanical tribological and corrosion resistant characteristics of the films formed are studied by SEM, XRD and microhardness analyses, and by scratch, impact, pin-on-disc friction and potentiodynamic corrosion testing. It is found that the films produced from the aluminate–phosphate electrolyte are dense and uniform and are composed mainly of Al₂TiO₅ and TiO₂ phases of the rutile form. The films possess a beneficial combination of 50–60 μm thickness, 575 kg/mm² hardness and high adhesion and provide a low wear rate (3.4×10⁻⁸ mm³/Nm) but a relatively high friction coefficient of μ=0.6–0.7 against steel, caused by material transfer from the counterface. A minimum friction coefficient of μ=0.18 is recorded during the testing of softer rutile–anatase films, 7 μm thick, produced from a phosphate electrolyte. Both of these types of film show good corrosion resistance in NaCl and physiological solutions, where the corrosion current is approximately 1.5 orders of magnitude lower than that of the uncoated substrate. SiO₂/TiO₂-based films with 70–90 μm thickness and high bulk porosity produced from silicate and silicate–aluminate electrolytes demonstrate better corrosion behaviour in H₂SO₄ solution, due to the greater chemical stability of the film phase components in this environment.     

铜在含氯薄液膜和杂色曲霉作用下的腐蚀行为

目的 研究纯铜在含氯液膜和霉菌共同作用下的腐蚀行为与机理。方法 将海南文昌采集的一株野生杂色曲霉接种到质量分数分别为0.9%和3.5%的NaCl溶液中制成孢子悬浮液,将孢子悬浮液均匀喷洒到铜试样表面后进行恒温恒湿试验,试验不同周期后采用体视学显微镜、扫描电子显微镜观察铜试样的腐蚀形貌,采用X射线光电子能谱仪分析试验14 d的试样表面和氩离子刻蚀15 s后的成分。结果 纯铜在NaCl薄液膜下的腐蚀产物具有明显的双层结构,内层靠近基体的为致密的Cu2O钝化层,外层为疏松的Cu2(OH)2CO3和Cu2(OH)3Cl组成的Cu(II)碱式盐;无菌时,铜表面出现大量蓝绿色的Cu(II)碱式盐,杂色曲霉存在时,铜表面腐蚀产物主要为红棕色的Cu2O钝化膜,仅有少量Cu(II)碱式盐零星分布在Cu2O膜外层;0.9% NaCl薄液膜与霉菌共同作用时,试样表面腐蚀产物主要为Cu2O,当薄液膜中盐的质量分数升高到3.5%时,霉菌数量减少,Cu(II)碱式盐较0.9% NaCl薄液膜组增多。结论 纯铜的腐蚀产物由内层的Cu2O钝化层、外层的Cu2(OH)2CO3和Cu2(OH)3Cl组成双层结构。杂色曲霉通过呼吸作用影响液膜中的O2浓度进而影响铜的腐蚀产物组成,霉菌存在时腐蚀产物中Cu(II)碱式盐显著减少。含氯液膜与霉菌共同作用时,液膜中的NaCl浓度通过影响杂色曲霉的生长活性而影响腐蚀产物组成。     

Electrochemical corrosion behavior of bronze materials in an acid-containing simulated atmospheric environment

The present work investigates the corrosion behavior of bronze materials under thin electrolyte layers (TELs) in a simulated atmospheric environment containing formic and acetic acid by electrochemical measurements as well as surface characterization. The results show that the corrosion of bronze under TEL is significantly faster than that in the bulk solution, and the corrosion rate of bronze is the highest when the thickness of TEL is about 100 μm. Formic acid is observed to be more corrosive than acetic acid. Copper formate and copper acetate hydrate appear in the corrosion products formed on the surface of bronze, suggesting that the organic acid participates in the corrosion process of bronze materials in the simulated atmospheric environment.     

复合气相缓蚀剂对铁质文物缓蚀机理的研究

采用乌洛脱品和胺类缓蚀剂A制成一种新的气相缓蚀剂,用模拟大气腐蚀状态的薄液膜电化学测试技术研究了复合气相缓蚀剂对铸铁试样电化学行为的影响.并通过X射线衍射(XRD)和X射线光电子能谱(XPS)分析了复合气相缓蚀剂作用于模拟带锈文物所形成的锈层结构,并探讨了其缓蚀机理.结果表明,该复合气相缓蚀剂是一种阳极型的气相缓蚀剂,对模拟带锈文物有很好的缓蚀效果,该缓蚀剂可以促进铁质文物中的不稳定锈层向稳定锈层转化,抑制基体腐蚀的进一步扩展,对铁质文物具有很好的保护作用.      

Effect of direct current electric field on atmospheric corrosion behavior of copper under thin electrolyte layer

A thin layer electrochemical cell was successfully developed to study the atmospheric corrosion behavior of copper film in printed circuit board (PCB-Cu) under thin electrolyte layer (TEL) and direct current electric field (DCEF) by electrochemical impedance and electrochemical noise analysis. The electrochemical measurements and SEM morphologies after corrosion test indicate that DCEF decreases the corrosion of PCB-Cu under TEL. The corrosion rate and probability of pitting corrosion of PCB-Cu under DCEF decrease due to the electric migration of aggressive Cl⁻ ion out of working electrode surface.     

Comparative study of the morphological degradation in nickel thin films exposed to H<Subscript>2</Subscript>S media and deposited by magnetron sputtering and electrolytic process

Nickel thin films with regular configuration and similar thickness were deposited on steel AISI 1018 (UNSG 10180) by two different techniques: magnetron sputtering and electrolytic process. The main aim of this work is to compare the surfaces deposited films made by the two techniques using the scanning electronic microscopy and to identify their morphological differences and imperfections. We evaluate the protective coatings properties when the films are in contact with an acid medium. We also study the thin films coatings by the spectroscopy impedance technique. We obtain that the sputtering deposits present a homogeneous thin film coating that is better than the one obtained by the electrolytic technique. It is expected that the thin film coatings made in this work can protect the steel against corrosion when it is in contact with an acid environment.     

Über die Werkstoffzerstörung durch Kavitation und Korrosion in Äthylenglykol-Wasser-Gemischen

The destruction of material through cavitation and corrosion in ethylene glycol-water mixes Destruction of structural parts in contact with liquids through cavitation and corrosion is the consequence of complex mechanical and corrosive stresses. In recent years, extensive research at model test beds has yielded information on the stress conditions encountered in waters. It was now intended to ascertain to what extent the destruction of material through cavitation and corrosion in ethylene glycol-water mixes differs from that in waters. For this purpose, tests have been carried out with magnetostrictive oscillators on grey cast iron and copper in water, in ethylene glycol, and in mixes of both liquids; the tests on grey cast iron were extended to solutions with inhibitor additives. It was found that the mechanical stress through cavitation is about the same in the liquids investigated. Certain differences in the destruction rate are mainly due to the high boiling point of ethylene glycol and the corrosion resistance of the material concerned. In aqueous ethylene glycol solutions as well as in water, the damage can be reduced by the addition of corrosion inhibitors.     

Plasma-enhanced chemical vapor deposition of polyperinaphthalene thin films

Plasma-enhanced chemical vapor deposition (PECVD) has been used to grow corrosion-resistive, semiconducting thin films of the graphite-like polymer polyperinaphthalene (PPN) from 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA). Unlike thermal chemical vapor deposition of PPN from PTCDA, where thin film growth is catalyzed by a transition metal substrate, PPN films have been grown by PECVD for the first time on non-catalytic substrates: indium tin oxide (ITO)-coated glass, aluminum and silicon. Films with the same morphology and molecular characteristics have also been grown on steel substrates, where iron functions as a growth catalyst. Potentiodynamic corrosion measurements in pH 5 water show that PPN films on steel provide an effective corrosion protection layer.     

Reaktionen zwischen Natriumpolysulfid und Stromabnehmermaterialien für Natrium/Schwefel-Batterien

Reactions between sodium polysulfide and materials for current feeds in sodium-sulfur batteries In order to measure corrosion rates of potential materials for current feeds in the sodium polysulfide melt of sodium-sulfur batteries changes with time of the thicknesses of thin films were measured using the 4-point resistance method. At the free corrosion potential the steady state corrosion rate of aluminium in Na₂S₄ at 350°C was ? 150 μm/a and the activation enthalpy around 300 kJ/mol. At sufficiently high cathodic currents the corrosion rates were observed to increase linearly with the square of the total current. Upon anodic polarisation the thickness of the passivating film was increased, but there was not much influence on the mean corrosion rate. However, there were indications of local differences of the corrosion rate. The steel X10CrA124 corroded by growth of a film according to the parabolic rate law until a steady state corrosion rate was attained being 90 μm/a at 350°C. The steel X10CrNiMoTi 18 10 not containing aluminium corroded at the rate of 1.5 mm/a. The corrosion rate of chromium was even higher. On the other hand, Stellite 6 and glassy carbon corroded at rates < 2 μm/a.     

Corrosion behaviour of polycrystalline Nb<Subscript>2</Subscript>O<Subscript>5</Subscript> thin films and its size effects

This study examines the effect of film thickness ranging from 230 to 404 nm on the corrosion resistance of Nb₂O₅ thin films grown by chemical solution deposition. The films were characterized to obtain the relationships between the deposition parameters and the most relevant physical properties (structural, surface morphology and corrosion resistance). From X-ray diffraction and XPS analyses we can conclude that the films were stoichiometric Nb₂O₅ and crystalline. The internal strain and morphology of the film changes as the number of layers increases indicating a thickness dependent grain size. The surface roughness, corrosion resistance were also affected by the film thickness. Electrochemical impedance spectroscopy (EIS) shows that the thicker film have higher passive and charge transfer resistance than the control samples. These results coating layer of Nb₂O₅ improves the corrosion resistance on an API 5L X80 steel alloy due to the formation of a film on the surface.     

NaCl和CO2对Zn在薄液膜下腐蚀的协同作用

使用石英晶体微天平（ＱＣＭ：ｑｕａｒｔｚ ｃｒｙｓｔａｌ ｍｉｃｒｏｂａｌａｎｃｅ）为主要手段研究了在８５％ＲＨ（相对湿度）和ＮａＣｌ存在的条件下,金属Ｚｎ在不同ＣＯ２浓度下的大气腐蚀动力学,同时结合Ｘ射线衍射（ＸＲＤ）和扫描电镜（ＳＥＭ）研究了Ｚｎ在薄液膜下的大气腐蚀机理,并用扫描电子显微镜（ＳＥＭ）对腐蚀产物进行形貌分析,阐述了腐蚀产物的保护特征。实验结果表明,在薄液膜下,ＮａＣｌ的存在使金属     

Investigation of kinetics of borided ductile and lamellar graphite cast iron

In this study, kinetics of borided ductile iron and lameller graphite grey cast iron were investigated by processing boronizing treatment (was carried out in Ekobor-II powders). The process temperatures and durations respectively 1123, 1173, 1223 K for 2, 4 and 6 hours, with pack boronizing method and under atmospheric pressure in electrical resistance furnace. Changing of borided layer properties was investigated by using optical and scanning electron microscopy, X-ray diffraction and micro-Vickers hardness testers. The growth kinetics of the boride layers forming and thickness of boride layer were computed for both cast iron. The main phases for two processes Fe₂B and FeB were defined on the surface.     

Über einige Aspekte der atmosphärischen Korrosion von Stahl

To some aspects of the atmospheric corrosion of steel The corrosion of unalloyed steel (St 38 u 2) in pure moist air and by existence of low molecular saturated monocarbonic acids have been studied with microphotometric method. Moreover the electrochemical behaviour of this steel in adequate aqueous solutions has been characterized. It was found that steel - in distinction to pure iron - corroded already in moist air without pollutants in case the relative humidity is (RH) ≥70%. The action of the volatile monocarbonic acids on the corrosion were dependent on the pH value of water film which had been absorbed on the oxide layer of iron material. Oxygen acted as passivator above of pH_crit and the anions of these carbonic acids stabilized the surface hydroxyl groups on the strength of formation of bridging complexes. Final general conclusions about the mechanism of the atmospheric corrosion of iron materials are deduced.     

Influences of NH4 + ions and thin electrolyte layers (TEL) thickness on the corrosion behavior of AZ91D magnesium alloy

In this study, the influences of NH₄ ⁺ ions and the thin electrolyte layer (TEL) thickness on the corrosion behavior of the AZ9D magnesium alloy in NH₄⁺‐containing environments were investigated by electrochemical measurements and surface characterization. The experimental results indicate that NH₄⁺ greatly accelerates the corrosion of AZ91D magnesium alloy whether in a bulk solution or in a TEL. As the TEL thickness decreasing, the corrosion resistance of the AZ91D magnesium alloy is strengthened. According to the corrosion morphology, electrochemical analysis, and characterization analysis of corrosion products, the corrosion mechanism of AZ91D under TELs with different thicknesses is divided into three stages: (a) uniformly distributed corrosion pits with deep depth and large size when TEL thickness is higher than or equal to 500 μm; (b) slightly corrosion with randomly distributed corrosion pits and the accumulation of small amount of corrosion product when TEL thickness is between 100 μm and 200 μm; (c) no corrosion pit with only deposition of corrosion product when TEL thickness is lower than or equal to 100 μm. Among which, the roles of NH₄⁺, TEL thickness, and corrosion product are emphasized and discussed in the corrosion process of AZ91D magnesium alloy under TEL with different thicknesses.     

Structure and mechanical properties of oxide films on zirconium alloys upon oxidation under different conditions

The structure and mechanical properties, as well as the mechanism and kinetics of the destruction of oxide films formed on tube specimens of E110 zirconium alloy based on electrolytic or sponge zirconium upon corrosion testing in an autoclave and high-temperature oxidation in steam (LOCA conditions), were studied with the use of transmission and scanning electron microscopy, microhardness measurements, acoustic emission, and fractography. Oxide films on specimens made of electrolytic zirconium upon testing in an autoclave are found to be composed of extended grains with a thickness of 100 nm, while those on sponge specimens are composed chiefly of equiaxial grains with a diameter of 30 nm. After high-temperature oxidation, the structure of oxide films consists of extended grains of a variable thickness, which increases from the surface to the film-metal boundary from 600 nm to 2.5 μm on specimens made of electrolytic zirconium and from 250 nm to 2 μm on sponge-zirconium specimens. The microhardness of films after testing in an autoclave is 1200 ± 50 HV on electrolytic zirconium and 2000 ± 50 HV on sponge zirconium. The hardness of films on sponge-zirconium specimens upon high-temperature oxidation is 1600 ± 50 HV. The combined analysis of deformation diagrams, fractures, and acoustic emission data showed that the destruction of thin oxide films after testing in an autoclave and that of thick films after high-temperature oxidation begins with the formation of transverse brittle ruptures at the same load of 12–15 MPa. The number of cracks in the films on specimens that underwent high-temperature oxidation increases under loading especially rapidly on electrolytic zirconium.