H2S/CO2环境中L360钢点蚀行为研究

利用静态挂片失重法研究了含H₂S/CO₂模拟油田水溶液中, 温度及Cl^-浓度对L360管线钢点蚀的影响, 并利用Gumbel第一类近似函数分析了最深蚀孔概率. 结果表明, 在40℃~70℃之间, Cl^-浓度为10 g/L条件下, 点蚀的严重程度随温度增高而增大. 恒定温度下, Cl^-浓度对点蚀发生也有明显的影响, 当Cl^-在10×15 g/L范围时, 腐蚀试样发生明显的点蚀; 当Cl^-浓度大于20 g/L时, 试样主要发生均匀腐蚀, 随着Cl^-浓度的增大, 腐蚀产物膜变得更加疏松, 保护性能下降, 均匀腐蚀速率增大. 最深点蚀分布服从Gumbel第一类近似函数.     

烟道气氨法脱硫液对Q235碳钢腐蚀研究

采用静态挂片、极化曲线和长期点蚀实验，研究了氨法脱硫浆液中F^-和Cl^-以及 (NH₄)₂SO₄对Q235碳钢腐蚀的影响。结果表明，Q235碳钢在含卤硫铵溶液中的均匀腐蚀速率随F^-浓度和Cl^-浓度增大均呈现先降低后增高的趋势，随着 (NH₄)₂SO₄质量分数增加，均匀腐蚀速率降低；随着F^-浓度的增大，自腐蚀倾向增加；随着Cl^-浓度以及 (NH₄)₂SO₄质量分数的增大，自腐蚀倾向均降低；Q235碳钢在氨法脱硫模拟浆液中点蚀较严重，需采取重防腐措施。     

铸造AZ91镁合金在CO32-/HCO3-体系中的应力腐蚀行为

用电化学实验、浸泡实验与慢应变速率拉伸实验研究铸造AZ91 镁合金在不同浓度比例的CO₃^2-/HCO₃^-溶液体系中的应力腐蚀(SCC)行为。结果表明,随着溶液pH值的升高,AZ91 镁合金的应力腐蚀敏感性降低。点蚀是AZ91镁合金在该实验体系下的裂纹萌生源,随着实验时间的延长,萌生于点蚀底部的微裂纹会逐渐扩展形成主裂纹,主裂纹靠吞并其前端的微裂纹向前扩展,直至发生SCC失效。     

Corrosion of AD31 (AA6063) Alloy in Chloride-Containing Solutions

Corrosion of AD31 (AA6063) alloy in neutral 0.05 M NaCl solutions is investigated via scanningprobe microscopy, linear-sweep voltammetry, and electrochemical-impedance spectroscopy. Al?Fe?Si?Mg intermetallic particles are determined to prevail in the structure of alloy and act as local cathodes. Intermodulation electrostatic-force-microscopy imaging shows that their Volta potential differs by 570 mV from that of the host aluminum matrix, making the alloy prone to localized corrosion. We show that the corrosion of alloy in the studied electrolyte mainly develops locally and results in pitting, with charge transfer being the limiting stage of the process. A mechanism of corrosion of the AD31 (AA6063) alloy in neutral chloride-containing solutions is proposed.     

HCO3-和SO42-对Cu点蚀行为的影响

在不同浓度配比的HCO₃^-和SO₄^2-混合溶液中,利用循环极化电化学测试方法和SEM,对Cu工作电极的循环极化行为和点蚀表面形貌进行了系统的研究.结果表明,在高电位范围的循环极化实验中,Cu的点蚀行为可分为活性溶解型点蚀和钝化膜破裂型点蚀;随SO₄^2-浓度的升高Cu点蚀的敏感性增大.由于HCO₃^-与SO₄^2-的协同作用,随HCO₂^-浓度升高点蚀敏感性呈先增大后减小的规律.在钝化膜破裂型点蚀中,SO₄^2-提高Cu点蚀的诱发能力;HCO₃^-降低Cu点蚀的诱发能力.2种离子对点蚀自修复能力的影响无明显规律.     

Synthesis and characterization of CoFe2O4 magnetic particles prepared by co-precipitation method: Effect of mixture procedures of initial solution

CoFe₂O₄ magnetic particles were prepared by co-precipitation method in 60 °C homogeneous aqueous solution without any subsequent heat treatment. It was found that the mixing procedure and Fe²⁺/Fe³⁺ ratio of initial solution were critical in the preparation of CoFe₂O₄ particles in particle size, magnetization characters, uniformity in particle size and even cation distribution in spinel structure. Two different procedures were used to precipitate CoFe₂O₄ magnetic particles. Evidenced by XRD, Mossbauer analyses and magnetization determination, particles in comparative uniformity average size were obtained in procedure A, denoted as normal pH regulation procedure, in which NaOH solution was dropped into the mixture solution of iron ions, and with the decreasing in Fe²⁺/Fe³⁺ ratio of initial solution, the particle size decreased, which followed the same rule of diversification in saturation magnetization. Uniformity in particle size lowered when procedure B, referred to as reverse pH regulation procedure, where ferrous and cobalt ions were dropped into alkaline solution, was used to precipitate CoFe₂O₄. In both procedures, with the decreasing in Fe²⁺/Fe³⁺ ratio of initial solution, the saturation magnetization decreased, while the magnetic coercivity decreased but increased sharply when Fe²⁺/Fe³⁺ ratio of initial solution was 0.     

Q235钢/导电混凝土在3种典型土壤环境中腐蚀的灰色关联度分析

采用动电位扫描和电化学阻抗谱(EIS)技术,研究了Q235钢/导电混凝土在盐碱土、黄棕壤、红壤中的腐蚀行为,分析了土壤环境因素对腐蚀过程的影响规律,并基于灰色关联度理论计算了土壤中各离子对导电混凝土中Q235钢腐蚀过程的影响权重.结果 表明,加速腐蚀45 d后,Q235钢/导电混凝土表面出现孔洞、边缘出现细微裂纹.Q2...     

Biosorption behaviors of Cu, Zn, Cd and mixture by waste activated sludge

Biosorption of heavy metal ions, such as Cu²⁺, Cd²⁺ and Zn²⁺, was carried out using waste activated sludge from municipal sewage treatment plant as adsorption material, and the effects of parameters, such as pH value, temperature, reaction time and sorption duration, were studied in detail. The results indicate that the removal rates of Cu²⁺, Zn²⁺ and Cd²⁺ with low concentration are 96.47%, 80% and 90%, respectively, adsorbed by waste activated sludge. Little effect of dosage of activated sludge on the adsorption of Cu²⁺ and more effects on the adsorption of Zn²⁺ and Cd²⁺ are observed. Little effect of temperature is observed, while pH value and adsorption time exert important influence on the sorption process. The adsorption behaviors of heavy metal ions all have parabolic relationships with pH value. The optimum pH value is between 6 and 10, and the optimum adsorption time is 1 h. In single heavy metal ion system, the sorption processes of Cu²⁺, Zn²⁺ and Cd²⁺ are in accordance with Freundlich model, which indicates that it is suitable for the treatment of these three heavy metal ions using intermittent operation. In addition, the sorption capacity of the sludge for Cu²⁺ is preferential to the other two ions.     

Role of strontium addition on the phase transition of lanthanum copper oxide from K2NiF4 to perovskite structure

Without Sr addition, the sintered La₂O₃ and CuO powder mixture in a mole ratio of 1:2 formed K₂NiF₄-structured La₂CuO₄ with excess CuO. When 15% of strontium was added, La₂CuO₄ transformed into the single perovskite La_1−xSr_xCuO_2.5−δ phase with orthorhombic structure. As the strontium addition increased to 20%, the perovskite lattice changed from orthorhombic to tetragonal. These phase transitions may be attributed to the enhanced oxidation of the divalent cupper ions (Cu²⁺) to trivalent ones (Cu³⁺) by the strontium addition. Based on the electroneutrality in an ABO₃ perovskite lattice, a divalent cation is unstable in the B-site cation sub-lattice when the A-site is occupied by a trivalent cation such as La³⁺. As strontium was added into the A-site cation sub-lattice, the oxidation of Cu²⁺ ion into trivalent Cu³⁺ ion was enhanced. The increase of Cu³⁺ concentration strengthened the electrostatic bonding (ESB) of copper ions with their neighboring anions. Consequently, the symmetrical tetragonal Sr-doped lanthanum copper oxide was obtained.     

预渗氮处理对20CrMnTi钢真空渗碳层耐蚀性能的影响

在真空渗碳前预先对20CrMnTi钢进行真空渗氮处理,采用OM、SEM和XRD研究了预渗氮处理对渗碳层显微组织及腐蚀形貌的影响,通过电化学测试和浸泡腐蚀质量损失来评价其耐蚀性能。结果表明,经过预渗氮处理的渗碳试样的渗层马氏体更加细小并且有大量渗碳体析出,耐腐蚀性明显提高,自腐蚀电流密度从1.3608×10^-5 mA·cm^-2下降到2.9817×10^-6 mA·cm^-2,自腐蚀电位由-0.7741 V提高到了-0.6672 V,其腐蚀速率和发生腐蚀的倾向大大降低,并且由质量损失得出的腐蚀速率仅为渗碳试样的一半。这主要是由于预渗氮+渗碳处理试样渗层细小的马氏体组织和渗碳体在腐蚀时会阻碍孔蚀的扩展从而降低腐蚀速率,并且渗层的氮原子会与溶液发生化学反应生成NH⁺₄及NO^-₂或NO^-₃,降低Cl^-对材料的腐蚀作用。     

O3/Cl-复合大气环境中Q235B钢的腐蚀演化特性

采用干/湿交替的实验方法模拟大气腐蚀过程。运用X射线衍射、电化学阻抗谱以及极化曲线等手段，研究了O₃/Cl^-复合大气环境中Q235B钢的腐蚀演化特性。结果表明，O₃和Cl^-的协同作用对Q235B钢的腐蚀有明显的促进作用，其腐蚀速率随着模拟环境中Cl^-含量的增加而增大。腐蚀演化特性方面，Q235B钢在腐蚀的初期阶段腐蚀速率最大，中期阶段腐蚀速率迅速下降，而到后期阶段腐蚀速率又有所提高。相比于不含O₃的大气环境，当Cl^-浓度较低时，O₃和Cl^-对Q235B钢腐蚀产物组份的影响并不明显。而当Cl^-浓度较高时，O₃和Cl^-能明显促进β-FeOOH的生成而抑制α-FeOOH和γ-FeOOH的生成。这说明O₃/Cl^-复合大气环境能促进Q235B钢的大气腐蚀与锈层相组分变化密切相关。     

2A12-T4铝合金在盐雾环境下的腐蚀行为与腐蚀机理研究

采用失重法、扫描电镜 (SEM)、X射线衍射仪 (XRD) 和电化学技术研究了2A12-T4铝合金在盐雾环境下的腐蚀规律及机理。结果表明：2A12-T4铝合金的腐蚀失重量与腐蚀时间符合幂指数函数规律。腐蚀初期,在Cl^-作用下2A12-T4合金发生点蚀,随后点蚀发展为全面腐蚀,电化学腐蚀产生大量Al(OH)₃导致疏松腐蚀产物层增厚;腐蚀中、后期,外层腐蚀产物发生脱落,剩余致密堆叠的腐蚀产物层。电化学测试表明,随着腐蚀时间的延长,2A12-T4合金的自腐蚀电流密度先减小后增大再减小,容抗弧先收缩后扩大,最后略有收缩。     

铝制冷板在乙二醇冷却液中的腐蚀行为

监测了冷板系统模拟装置冷却液的p H和铝离子含量,分析了冷板的腐蚀形貌和腐蚀产物,研究了6063铝合金冷板在乙二醇冷却液中的腐蚀行为及导电氧化处理对6063铝合金(6063-CCO)冷板腐蚀行为的影响。结果表明:在试验时间内,冷却液的p H增大,其中试验初期增加明显,后增加缓慢,趋于稳定;铝合金基体金属腐蚀产生的铝离子进入溶液和形成沉淀之间会形成动态平衡;铝制冷板在乙二醇冷却液中的腐蚀以点蚀为主,其腐蚀速率随试验时间的增加而减小,其中试验初期,6063-CCO冷板的腐蚀速率更低,但试验后期,其腐蚀速率却更大。     

Cu2+及等离子电解氧化处理对Zr-4合金腐蚀性能的影响

采用电化学方法研究锆合金Zr-4在添加不同Cu2+浓度的0.5 mol/L NaCl溶液或0.5 mol/L Na2SO4中的腐蚀行为,探讨不同浓度Cu2+对Zr-4合金腐蚀性能的影响,同时,在10 g/L Na2SiO3.9H2O+10 g/L Na4P2O7.10H2O混合溶液中对Zr-4合金进行等离子电解氧化处理,并用极化曲线技术研究膜层的防护能力。结果表明:Cu2+能使Zr-4合金自腐蚀电位正移,降低极化曲线上钝化区的宽度,使得合金的抗孔蚀能力降低,腐蚀电流密度增加;在硫酸钠溶液中,Cu2+的添加没有使合金产生明显的孔蚀,这表明Zr-4合金的抗孔蚀能力下降是Cu2+和Cl共同作用的结果;等离子电解氧化处理能够大幅度提高Zr-4合金的抗孔蚀能力。     

300M和Cr9钢在酸性介质中的电化学性能研究

采用动电位极化、电化学阻抗和金相显微技术研究了300M和一种新型超高强度马氏体钢 (简称Cr9钢)在(H₂SO₄+Na₂SO₄)溶液中的腐蚀规律,以及pH值和Cl^-对其腐蚀行为的影响。研究表明,300M和Cr9钢的腐蚀电位E_corr随pH值增大呈升高趋势,电荷转移电阻R_ct减小,腐蚀电流密度I_corr增大。溶液pH值的降低能加速300M和Cr9钢的腐蚀。在无Cl^-的(H₂SO₄+Na₂SO₄)溶液中,300M发生均匀腐蚀,而Cr9钢则表现为点蚀;Cl^-能促进点蚀的发生,使Cr9钢的阳极反应由钝化转变为活化溶解。Cr9钢中Cr、Mo和Ni元素含量的增加能提高其在酸性介质中的耐蚀性,腐蚀速率明显低于300M钢。     

An integrated study on the effect of pre- and post-extrusion heat treatments and surface treatment on the filiform corrosion properties of an aluminium extrusion alloy

The effect of pre- and post-extrusion heat treatments on the filiform corrosion behaviour of a well-known aluminium extrusion alloy AA6063 is studied by a combination of accelerated filiform corrosion exposure tests and potentiodynamic polarisation measurements for four different surface treatments. It is shown that the post-extrusion heat treatment of this AlMgSi alloy can influence the filiform corrosion properties significantly, in particular for the milder surface treatments. In contrast, the relative effect of the pre-extrusion treatment on the filiform corrosion properties is minimal for all treatments. The alloys are most susceptible to filiform corrosion in the β′ condition. The susceptibility decreases with coarsening of the Mg₂Si particle distribution. For the post-extrusion heat and surface treated AA6063 material a clear correlation between the polarisation characteristics and the two principal filiform corrosion characteristics, i.e. the propagation rate and total area of attack after accelerated exposure, is observed. The observed correlation is attributed to a pitting corrosion mechanism with a rate depending on the (coupled) Mg₂Si precipitate size and fraction.     

Effects of pH and chloride concentration on pitting corrosion of AA6061 aluminum alloy

Effects of pH solution and chloride (Cl⁻) ion concentration on the corrosion behaviour of alloy AA6061 immersed in aqueous solutions of NaCl have been investigated using measurements of weight loss, potentiodynamic polarisation, linear polarisation, cyclic polarisation experiment combined with open circuit potential transient technique and optical or scanning electron microscopy.The corrosion behaviour of the AA6061 aluminum alloy was found to be dependant on the pH and chloride concentration [NaCl] of solution. In acidic or slightly neutral solutions, general and pitting corrosion occurred simultaneously. In contrast, exposure to alkaline solutions results in general corrosion. Experience revealed that the alloy AA6061 was susceptible to pitting corrosion in all chloride solution of concentration ranging between 0.003 wt% and 5.5 wt% NaCl and an increase in the chloride concentration slightly shifted both the pitting E_pit and corrosion E_cor potentials to more active values. In function of the conditions of treatment, the sheets of the alloy AA6061 undergo two types of localised corrosion process, leading to the formation of hemispherical and crystallographic pits.Polarisation resistance measurements in acidic (pH = 2) and alkaline chloride solutions (pH = 12) which are in good agreement with those of weight loss, show that the corrosion kinetic is minimised in slightly neutral solutions (pH = 6).     

几种阴离子对A3钢在NaHCO_3+NaCl溶液中亚稳态孔蚀行为的影响

用动电位极化法研究了CO32-、NO2-、SO42-、MoO42-和PO43-5种阴离子对A3钢在0.5 mol/L NaHCO3+0.05mol/L NaCl溶液中的亚稳态孔蚀行为.5种离子使A3钢的孔蚀电位Eb和亚稳孔蚀出现电位Em均不同程度地正移,说明这5种离子既抑制稳定孔蚀的发生,也抑制亚稳孔蚀的发生.在5种离子中,NO2-抑制亚稳孔蚀形核的能力最强.5种离子对稳定孔蚀与亚稳孔蚀形核与生长有大致相同的作用.     

Influence of pre-treatments in cerium conversion treatment of AA2024-T3 and 7075-T6 alloys

The role of pre-treatment in the formation of a cerium conversion coating is investigated for the protection of AA2024-T3 and 7075-T6 alloys. The alloys were alkaline-etched and de-smutted in nitric acid, prior to cerium treatment in Ce(NO₃)₃ at 85 °C with H₂O₂ accelerator. Potentiodynamic polarization studies in 3.5% NaCl solution revealed a large shift of  300 mV of the corrosion potential below the pitting potential for the 7075-T6 alloy, which correlated with the development of a finely-textured, uniform coating. However, the formation of a uniform coating and protection was dependent upon the time of de-smutting, with non-uniform coatings resulting from extended times of de-smutting. In contrast, non-uniform coatings developed on the 2024-T3 alloy, with pitting potential at the corrosion potential, irrespective of the time of de-smutting. Findings for the 2024-T3 alloy indicate that extended de-smutting affects the enrichment of alloying elements.     

Pitting and stress corrosion cracking resistance of friction stir welded AA 5083

The corrosion behaviour of friction stir welded (FSW) joints of AA 5083 has been compared to that of MIG welded joints. Pitting and stress corrosion cracking (SCC) resistance in 3.5% NaCl + 0.3 g/l H₂O₂ and in EXCO (4 M KCl + 0.5 M KNO₃ + 0.1 M HNO₃) solutions has been determined at 25°C. SCC susceptibility was evaluated by slow strain rate tests (SSRT), at a strain rate of 1 × 10⁻⁶ s⁻¹.Welds obtained by FSW technique showed a higher corrosion resistance in EXCO solution and a lower pitting tendency than the base alloy. Electrochemical measurements (corrosion potential measurements, polarization curves recording) evidenced that FSW weld was cathodic to base alloy. FSW joints were not susceptible to SCC in both test solutions, whereas MIG joints cracked in both solutions.