Zn(NO3 ) 2 ·6H2O,Na2MoO4 ·2H2O 与 Na5P3O10对 1Cr18Ni9Ti 的协同缓蚀作用

目的研究硝酸锌、钼酸钠及三聚磷酸钠之间的协同缓蚀作用机理,使其在性能上实现互补。方法以酸性高锰酸钾溶液为基础,通过极化曲线和失重法实验,研究3种缓蚀剂对1Cr18Ni9Ti奥氏体不锈钢的协同缓蚀作用。结果硝酸锌和三聚磷酸钠以抑制不锈钢的阴极反应为主,钼酸钠则主要抑制不锈钢的阳极反应。硝酸锌与钼酸钠表现出明显的拮抗作用,导致缓蚀效果变差。只有当三聚磷酸钠加入后,三者之间才表现出了良好的协同作用,使总的缓蚀性能达到最优,复配后的缓蚀效率可以达到90%以上。结论硝酸锌、钼酸钠及三聚磷酸钠之间存在良好的协同缓蚀作用,可以明显降低1Cr18Ni9Ti不锈钢在酸性高锰酸钾溶液中腐蚀速率,从而延长设备的使用寿命。     

EIS characterisation of anodic films formed on 2024 aluminium alloy, in sulphuric acid containing molybdate or permanganate species

Electrolytes composed of sulphuric acid and corrosion inhibitors (molybdate or permanganate species) were proposed in order to replace chromic acid for the anodising of 2024 aluminium alloy. The electrochemical impedance spectroscopy (EIS) method was used to visualise the correlation between the corrosion performance in NaCl and the morphology of these new anodic layers. From an appropriate equivalent circuit, EIS parameters concerning the porous and barrier layers were detected. Their evolution during corrosion tests was discussed. The results indicate that the morphology and the corrosion resistance of anodic films formed in acid sulphuric with molybdate species remain unchanged. On the contrary, morphological properties of anodic films formed in presence of permanganate species are modified, favouring their corrosion performance. EIS analyses were completed with SEM technique.     

Alternative conversion coatings to chromate for the protection of magnesium alloys

Chromium Conversion Coatings (CCCs) are widely used for the protection of magnesium alloys against the corrosion but this approach is limited due to the toxicity of hexavalent chromium. Alternative conversion coatings are based on solutions containing chromium (III), permanganate, phosphates, Rare Earth Elements (REEs) or vanadium. This review details the deposition and protection mechanisms of CCC technology and other promising processes. Permanganate/phosphate-based coating presents a corrosion resistance equivalent to CCC and REEs have self-healing properties but no coating present all the properties of CCCs. The development of new non-toxic conversion coatings remains a priority.     

模拟炼油环境中Q235钢和Cr5Mo钢表面硫化物膜稳定性及动态冲刷腐蚀行为研究

通过静态浸泡腐蚀实验装置和高温动态冲刷实验装置分别研究了硫化物膜在多种模拟炼油介质中的稳定性以及动态冲刷条件下Q235钢和Cr5Mo钢的耐冲刷腐蚀性能。结果表明,硫化物膜的形成过程是一个动态平衡过程。在无硫补充的条件下,硫化物膜快速溶解。动态冲刷作用下,Cr5Mo钢耐动态环烷酸冲刷腐蚀性能明显好于Q235钢,溶液酸值越大两者的差别越明显。     

Electrochemical study of inhibitor-containing organic-inorganic hybrid coatings on AA2024

Use of organic-inorganic hybrid sol-gel thin films is recently reported among the most promising approaches for the replacement of chromate based pre-treatment methods for high strength structural aluminium parts.To be applied in the aerospace industry, pre-treatments have to meet the demanding requirements and must be compatible to state of the art paint systems. The addition of inhibitive species is desirable for the active corrosion protection and the prevention of sub-surface migration at defect sites of the coating.In the present work hybrid films were produced by the controllable sol-gel route. Corrosion inhibitors were incorporated to the coatings in order to provide active protective effect. The barrier properties and the active corrosion protection on AA2024-T3 have been studied by Electrochemical Impedance Spectroscopy and Scanning Vibrating Electrode Technique. The obtained results were proven by conventional accelerated tests such as neutral salt spray test confirming validity of the mentioned electrochemical techniques for the evaluation of protection efficiency of hybrid sol-gel films.The addition of inhibitors to sol-gel coatings in most cases leads to an improvement of the active corrosion protection but on the other hand it may negatively influences the barrier properties of the films. Therefore, encapsulation of the inhibiting compounds is beneficial in order to combine the good barrier function of the coating with the corrosion mitigating effect of the inhibitors.     

Self-assembling molecules as corrosion inhibitors for 1050 aluminum

Whether it contains hexavalent chromium, chromium (VI), or simply Cr(VI), chromating has been largely used for surface preparation of aluminum aimed at corrosion protection due to its effectiveness and easy application. The most used among these processes are those that contain toxic and carcinogenic substances, which generate environmental backlash concerning the disposal of used baths with toxic elements. The high costs involved in the treatment of the disposal solutions prior to being discarded, besides the increasing restrictions concerning the environment, have encouraged research in the search for alternatives with lower toxicities than chromating processes but with high effectiveness for corrosion protection. Surface treatments with alkane diphosphonate molecules (ADM) have been investigated as potential substitutes for chromating. However, their effectiveness in the corrosion protection of aluminum alloys still needs further investigation. In the present study, the corrosion resistance of 1050 aluminum with various surface treatments was investigated by electrochemical techniques and salt spray testing. The corrosion performance of 1050 aluminum samples with a surface treatment that consisted of immersion in ADM was compared with that of the same alloy chromated by immersion in baths of Cr(III) or Cr(VI). The results showed that surface treatment with ADM was effective on samples that had been exposed to boiling water for oxide growth prior to treatment with ADM. The results also showed the superior corrosion performance for samples with the oxide-hydroxide + ADM surface treatment compared to those with both chromating treatments, either with Cr(III) or with Cr(VI). Cr(III) chromating treatment also provided better corrosion performance than chromating with Cr(VI), suggesting that both surface treatments (oxide-hydroxide + ADM and Cr(III)) are potential candidates for substitution for Cr(VI)-containing processes. However, for effective corrosion protection, the ADM treatment has to be carried out on surfaces previously exposed to treatments that favor oxide growth.     

Surface Characterisation Studies of CrVI and CrIII Electroplated Carbon Steel Samples

Conventional Nickel-Chromium (VI) electroplating has played an important role for corrosion protection of carbon steel blades used in ice-skating for many decades. However, in recent years, the exposure limits for humans to chromium (VI) compounds have been further reduced due to their toxicity and carcinogenic nature, which makes the use of hexavalent chromium electroplating less likely in the future.

It is envisaged that environmentally acceptable Nickel-Chromium (III) electroplating will be a suitable replacement. In this study, Nickel-Chromium (VI) and Nickel-Chromium (III) electroplating have been applied to carbon steel blades. Electrochemical tests were carried out on both Cr(VI) and Cr(III) electroplated blades to evaluate their anti-corrosion performance. In addition, Atomic Force Microscopy and Scanning Electron Microscopy were used to investigate the surface characteristics of the electroplated samples before and after accelerated corrosion tests. It was found that Cr(III) deposits had the lower surface roughness but exhibited higher corrosion rates than Cr(IV). This difference was attributed to multiple pit formation and coalescence in the Cr(III) coating.     

Oxidising type inhibitors for protection of aluminium and steel surfaces in sodium chloride solutions

Abstract

Photoelectron spectroscopy was used to study the composition of surface films formed on aluminium and steel when protected from corrosion in aqueous chloride media by inorganic inhibitors of the MeO^2?₄ oxidising type and by mixtures of these and monoethanolamine (MEA). The surface condition plays a significant role in the protection of aluminium. In the adsorption of molybdate on to an etched surface reduction of Ma(VI) to Mo(IV) occurs whereas on an unetched surface, as also for a steel surface, no reduction occurs. In the case of chromate, reduction to Cr( III) took place on steel and on aluminium. Synergism was established in the inhibition of corrosion of steel by a combination of inorganic oxidisers and MEA and a study made of this phenomenon.     

Corrosion behavior of Cr electrodeposited from Cr(VI) and Cr(III)-baths using direct (DCD) and pulse electrodeposition (PED) techniques

A comparison was made between the electrochemical corrosion behaviors of chromium deposited from hexavalent [Cr(VI)] and trivalent [Cr(III)] chromium baths using direct current (DCD) and pulse electro deposited (PED) techniques. Chromium coatings were deposited on mild-steel (MS) substrate. The corrosion behavior of both DCD and PED chromium from Cr(VI) and Cr(III)-baths in 3.5%NaCl solution was studied using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results indicated that PED chromium from Cr(VI) and Cr(III)-baths have higher charge-transfer resistance R_ct and very low I_corr than that of DCD chromium on mild-steel substrate.     

无铬复合钝化膜的微观组织结构及耐腐蚀性能

目的解决热镀锌钢板表面六价铬钝化工艺所产生的环境污染问题。方法以钼酸铵、纳米硅溶胶、单宁酸、硅烷偶联剂KH151和KH792为主要原料配制新型环保的无铬复合钝化液,在镀锌板表面制备钝化膜。采用扫描电子显微镜(SEM)、能谱仪(EDS)和X射线光电子能谱仪(XPS)分析无铬复合钝化膜表面的微观形貌、元素组成和化学成分,用电化学工作站测试Mo元素对镀锌板耐蚀性的影响,使用中性盐雾实验研究不同皮模量时膜层的耐蚀性。结果无铬复合钝化膜中的Mo元素可以抑制微裂纹的产生和发展,阻挡腐蚀性介质向金属基体扩散,提高复合硅烷膜的电阻。复合钝化膜的电化学交流阻抗比硅烷钝化膜提高了1.6倍,与六价铬钝化膜接近,可以有效抑制腐蚀电化学反应的发生,降低反应速度,提高膜层的耐蚀性。皮膜量为892 mg/m2时,膜层的腐蚀面积为0,耐蚀性达到六价铬钝化膜水平;皮膜量为1252 mg/m2时,耐蚀性能优异。结论制备的无铬复合钝化膜结合了硅烷钝化膜和钼酸盐钝化膜两方面的优点,提高了膜层的致密性和结合性,膜层耐腐蚀性接近/达到了六价铬钝化的效果。     

Features of electroplating of nanocrystalline chromium coatings from electrolytes based on Cr(III)

It is shown that, for the development of new chrome-plating technologies, it is necessary to proceed from the complicated Cr(III) chemistry. The analysis of the complexation processes of Cr(III) with hydroxycarboxylic acids in aqueous solutions is given. The results of investigations of deposition processes of chromium coatings from sulfate, oxalate–sulfate, and formate–glycine electrolytes are presented. Thin chromium films, as well as chromium films alloyed with cobalt, are obtained from formate–glycine electrolyte. With the use of atomic-force microscopy, it is shown that the formed chromium films are bright and possess a nanocrystalline structure and codeposition of chromium and cobalt leads to the formation of a more uniform structure.     

硫酸钙沉积导致铁基和镍基合金的热腐蚀

作者在几种铁基和镍基高温合金的试样上涂硫酸钙盐膜在1000℃及1150℃加热研究了硫酸钙对这些合金热腐蚀的影响。测定了这些合金的高温腐蚀动力学曲线。对腐蚀产物进行了 X 射线衍射、电子衍射、电子探针分析及金相检查。实验结果证明:由硫酸钙沉积导致的热腐蚀与合金成份有密切的关系。温度愈高,盐膜愈厚,腐蚀也愈严重。含钼又有足够铝含量以生成 Al_2O_3氧化皮的合金,由于 Al_2O_3被 MoO_3酸性熔融,与 CaSO_4反应可能生成液态的 CaMoO_4,会发生严重的腐蚀。合金的铬含量增高会提高抗 CaSO_4沉积腐蚀的能力,抗蚀性原来不好的合金渗铬后抗蚀性亦显著提高。     

Life extension of trivalent chromium passivation baths and enhanced product performance

Abstract

Although Cr (III) based passivation processes are mature, there is always pressure from end users to improve the performance of passivation films. The effect of incorporating ceramic nanoparticles into the film on the corrosion protection of steel components is reported for zinc coatings, with particular emphasis on cobalt-free processes. A novel technology based on selective ion-exchange to remove contaminants such as iron and copper as well as dissolved zinc from trivalent chromium baths is also described. Removal of these metals simultaneously without any appreciable reduction in chromium concentration rejuvenates the system and increases bath life significantly. This reduces not only the cost of frequent make-ups but also the load on the effluent treatment system, and imparts greater consistency to the life and appearance of the components processed. The concept can be extended to baths for chromating of aluminium and its alloys. Technical data generated from actual industrial installations are presented and discussed.     

An X-ray photo-electron spectroscopic study on the role of molybdenum in increasing the corrosion resistance of ferritic stainless steels in HC1

X-ray photo-electron spectroscopy has been used to investigate the correlation between composition of surface films and the beneficial effects of molybdenum addition to high purity, 30Cr ferritic stainless steels in improving the corrosion resistance properties in HCI. It has been found that the passive films formed consist mainly of hydrated chromium oxy-hydroxide and the composition of the films on 30Cr and 30Cr-2Mo stainless steels is essentially the same, except for the existence of a small amount of hexavalent molybdenum on the latter steel. The surface film formed in the active region contains a large amount of hexavalent molybdenum. The beneficial effects of molybdenum have been interpreted as follows: molybdenum eliminates the active surface sites through the formation of molybdenum oxy-hydroxide or molybdate on these site, on which it is difficult to form the stable passive film. This leads to the appearance of a homogeneous steel surface and to the formation of a homogeneous passive film.     

Influence of electrodeposition potential,TiO2 nanoparticles and chromium (III) inhibitor addition on the corrosion protection performance of organosilane coating on aluminium

In this work, the anticorrosion properties of phenyl trimethoxysilane (PTMS) films coated on aluminium 5000 series alloys were studied. PTMS films were deposited at various cathodic potentials. The optimum electrodeposition potential was found to be ?0.8?V vs. SCE. The coatings were also modified by different amounts of nano-TiO₂. In order to introduce corrosion inhibition and a self-repair property of the PTMS film, the addition of chromium (III) corrosion inhibitor in the presence of nano-TiO₂ was studied. The anticorrosion performance of coatings was investigated in a 3.5 wt.% NaCl solution. At optimum deposition potential, the ‘critical’ nano-TiO₂ and Cr(III) contents were both observed, under which the obtained PTMS coatings show the highest anticorrosion performance. The surface morphologies of PTMS coatings were examined by scanning electron microscopy. The results showed that the coatings deposited at ?0.8?V vs. SCE, from 20?ppm of nano-TiO₂ and 0.003 M Cr(III) inhibitor present uniform and compact morphologies.     

Electrochemical and In Vitro Behavior of Nanostructure Sol-Gel Coated 316L Stainless Steel Incorporated with Rosemary Extract

The corrosion resistance of AISI 316L stainless steel for biomedical applications, was significantly enhanced by means of hybrid organic-inorganic sol-gel thin films deposited by spin-coating. Thin films of less than 100 nm with different hybrid characters were obtained by incorporating rosemary extract as green corrosion inhibitor. The morphology, composition, and adhesion of hybrid sol-gel coatings have been examined by SEM, EDX, and pull-off test, respectively. Addition of high additive concentrations (0.1%) did not disorganize the sol-gel network. Direct pull-off test recorded a mean coating-substrate bonding strength larger than 21.2 MPa for the hybrid sol-gel coating. The effect of rosemary extract, with various added concentrations from 0.012 to 0.1%, on the anticorrosion properties of sol-gel films have been characterized by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests in simulated body fluid (SBF) solution and has been compared to the bare metal. Rosemary extract additions (0.05%) have significantly increased the corrosion protection of the sol-gel thin film to higher than 90%. The in vitro bioactivity of prepared films indicates that hydroxyapatite nuclei can form and grow on the surface of the doped sol-gel thin films. The present study shows that due to their excellent anticorrosion properties, bioactivity and bonding strength to substrate, doped sol-gel thin films are practical hybrid films in biomedical applications.     

The corrosion-protective traits of electroplated multilayer zinc-iron-chromium deposits

A novel kind of three-layer zinciron-cbromium electroplated coating was tested and proven to possess good corrosion protective characteristic as well as acceptable decorative properties. A citric-chloride bath containing Fe(III)-complexes is suggested for electrodeposition of iron intermediate layer on the zinc deposit surface. Due to the low acidity (pH 5) and medium operating temperature (20-30°C), the electrolyte involved has no a strong etching effect and can be used for direct iron deposition on zinc. A finish chromium layer is deposited from formate-sulfate trivalent bath. The zinc layer corrodes through the pores of Fe and Cr layers and protects the steel substrate against corrosion. The iron and chromium layers decelerate the corrosion rate of zinc. The finish chromium layer provides with good decorative properties, and the intermediate iron layer ensures adhesion of chromium to the zinc.     

The Corrosion Resistance of Chromium Electroplated from Trivalent and Hexavalent Chromium Plating Solutions

A comparison has been made of the long term stability and corrosion resistance of trivalent chromium deposited from a chloride based solution and hexavalent chromium deposited from a sulphate based solution. The work showed a difference in corrosion resistance between the two systems and has revealed the corrosion mechanism that caused the failure of the plated films. All the work was carried out on a brass substrate overplated with bright nickel to provide a substrate for the chromium deposit.     

Effect of exposure time on the morphology of corrosion on high chromium white cast iron in high temperature caustic solutions

High chromium white irons are important candidate materials for use in alumina refineries to combat wear and corrosion. The effect of exposure time on the formation of oxide films was studied in a 23% Cr white cast iron exposed at 260 °C in 110 g/l caustic soda solutions. It was found that whilst well‐formed octahedral M(II)O.M(III)₂O₃ spinel type oxides initially formed and spread across the surface of the material, these were gradually replaced by a background oxide with a higher Cr/Fe ratio and the morphology of the octahedral crystals became less well formed. Also, the oxidation was found to be predominantly in the matrix material, leaving carbide particles unsupported on the surface and in the later stages, significant corrosion was found along the carbide/matrix phase boundary.     

含铬油套管钢材在CO2和微量H2S共存环境中的腐蚀规律

目的 研究不同含铬材质钢在CO2和微量H2S共存环境中的腐蚀行为，优化深井油套管抗腐蚀设计方案。方法 以实际油水分离的水样为腐蚀介质进行模拟实验，采用高温高压反应釜、扫描电子显微镜(SEM)和X射线能谱仪(EDS)，揭示4种含铬材质钢在不同腐蚀环境中的腐蚀速率、腐蚀产物膜及应力腐蚀开裂特征，并建立高CO2与微量H2S共存环境下油套管防腐选材优化设计方法。结果 在高分压比条件下均发生了由CO2主导的腐蚀反应，腐蚀产物以FeCO3为主，加入微量H2S后低Cr材质产物膜的附着力较低，出现了疏松脱落现象，FeS优先成膜，含铬钢表面的腐蚀产物膜呈现“富铬”现象，膜的保护性能得到改善。3种腐蚀环境中3Cr钢对应的腐蚀速率分别为1.965 3、1.736 1、1.159 2 mm/a，均处于极严重程度，且表面出现了局部沟槽;9Cr钢的产物膜轻微覆盖，腐蚀较轻，13Cr和S13Cr基本无产物膜覆盖，未发生腐蚀。9Cr、13Cr和S13Cr在加载90%的屈服应力时均未发生应力腐蚀开裂，应力腐蚀敏感性较低。结论 含铬钢具有良好的抗腐蚀性能，基于腐蚀环境特点提出了井筒分段防腐选材设计方案“9Cr+13Cr+超级13Cr”，有效降低了防腐成本，研究结果对CO2和微量H2S共存环境中含Cr钢腐蚀特征和优化选材提供了理论依据。