维尼纶醛化机腐蚀监控技术的研究

本文研究SUS36不锈钢,在醛化液中的腐蚀行为及电化学条件、介质中的杂质离子浓度等因素的影响。提出了醛化机不锈钢腐蚀监控的参数。结果表明,在Cl~-浓度小于600pm的醛化液中,采用恒电位(300mV左右)阳极保护,能有效地控制腐蚀。本文还给出维尼纶醛化机不锈钢设备恒电位阳极保护装置的工艺设计及工业应用试验结果。     

阳极钝化电位对黄铜表面钝化膜半导体性能的影响

目的研究黄铜在不同阳极钝化电位下形成的钝化膜的半导体性能。方法通过动电位极化曲线获取黄铜在硼酸盐缓冲溶液中的维钝电位区间,并选取3个钝化电位值对黄铜进行钝化处理,采用电化学阻抗谱和Mott-Schottky半导体理论研究阳极钝化电位对钝化膜半导体性能的影响,并进一步利用PDM模型进行点缺陷扩散系数的计算。结果黄铜在硼酸盐缓冲溶液中有明显的钝化区间,不同钝化电位对应的Mott-Schottky直线斜率均为负值,且点缺陷扩散系数均为10-14数量级。随着阳极钝化电位的正移,钝化膜的阻抗值不断增加,受主密度降低,平带电位变小,空间电荷层厚度增加。结论黄铜在不同钝化电位下形成的钝化膜均表现出p型半导体的特性,膜中载流子以空穴为主,随着阳极钝化电位的正移,钝化膜的导电性能变差,耐蚀性能增强,对基体的保护作用更好。     

普通低碳钢与细晶粒钢钝化膜在碱性介质中的耐蚀性

应用循环伏安与动电位极化曲线确定普通低碳钢与细晶粒钢在碱性介质(模拟混凝上孔隙液)中的钝化区域.利用计时电流法在选取的阳极极化电位下使钢筋生成稳定的钝化膜,并通过电化学阻抗谱、Mott-Schottky曲线比较了钢筋在不同阳极电位下形成的钝化膜的优劣性;其次,循环极化曲线对比分析了在有无Cl~-存在时普通低碳钢与细晶粒钢钝化膜的耐蚀性.结果表明,2种钢筋的公共钝化电位区域为-0.25—+0.6V,在选取的+0.3V阳极极化电位下2者均能形成更稳定的钝化膜.在无Cl~-存在的条件下,细晶粒钢钝化膜的稳定性与耐蚀性均略优于普通低碳钢;但有Cl~-存在时,细晶粒钢抑制Cl~-点蚀的能力稍弱于普通低碳钢.影响细晶粒钢钝化膜耐蚀性的主要原因是晶界数量与微量元素含量.     

H2S水溶液中的腐蚀与缓蚀作用机理的研究Ⅳ．碱性硫化物溶液中Cl-对碳钢钝化行为的影响

利用交流阻抗和动电位极化技术,在碱性硫化物溶液中,分别研究了阳极极化电位下 对 低碳钢钝化过程阻抗行为的影响,钝化膜临界孔蚀电位 与 浓度的关系以及临界 浓度随 温度的变化．结果表明,在除氧的碱性硫化物溶液中,阳极极化的初期阻抗具有两个时间常数,随极化电位的升高,钝化膜逐步趋于完整;在点蚀的形成过程中,容抗弧半径逐渐变小,当极化电位为-600mV时容抗弧半径大幅度下降,并出现低频实部电感性收缩现象;在点蚀形成后的发展阶段,容抗弧半径继续减小,阻抗谱出现两个时间常数的双容抗弧．极化研究结果表明,不同温度下,随介质Cl-浓度增加,电极表面的钝化倾向降低,临界孔蚀电位随Cl-浓度增加而线性正移．     

H2S水溶液中的腐蚀与缓蚀作用机理的研究——Ⅳ.碱性 ？…

利用交流阻抗和动电位极化技术，在碱性硫化物溶液中，分别研究了阳极极化电位下Ｃｌ＾－对低碳钢钝化过程阻抗行为的影响，钝化膜临界孔蚀电位Ｅｂ与Ｃｌ＾－浓度的关系以及临界Ｃｌ＾－浓度随温度的变化。结果表明，在除氧的碱性硫化物溶液中，阳极极化的初期阻抗具有两个时间常数，随极化电位的升高，钝化膜逐步趋于完整；在点蚀的形成过程中，容抗弧半径逐渐变小，当极化电位为－６００ｍＶ时容抗弧半径大幅度下降，并出现低频实     

H2S水溶液中的腐蚀与缓蚀作用机理的研究Ⅳ．碱性硫化物溶液中Cl-对碳钢钝化行为的影响

利用交流阻抗和动电位极化技术,在碱性硫化物溶液中,分别研究了阳极极化电位下Ｃｌ~对低碳钢钝化过程阻抗行为的影响,钝化膜临界孔蚀电位Ｅｂ与Ｃｌ浓度的关系以及临界ＣＩ~浓度随温度的变化．结果表明,在除氧的碱性硫化物溶液中,阳极极化的初期阻抗具有两个时间常数,随极化电位的升高,钝化膜逐步趋于完整;在点蚀的形成过程中,容抗弧半径逐渐变小,当极化电位为－６００ｍＶ时容抗弧半径大幅度下降,并出现低频实部电感性收缩现象;在点蚀形成后的发展阶段,容抗弧半径继续减小,阻抗谱出现两个时间常数的双容抗弧．极化研究结果表明,不同温度下,随介质Ｃｌ~浓度增加,电极表面的钝化倾向降低,临界孔蚀电位随Ｃｌ~浓度增加而线性正移．     

晶粒度与介质中Cl~-浓度对铜表面钝化膜的影响

采用电化学方法以及Mott-schottky理论,研究了两种不同晶粒大小的铜在不同Cl-浓度溶液中的钝化膜形成过程和机理,计算了不同Cl-浓度溶液中铜在0.2V、0.4V两种电位下阳极氧化后钝化膜中的载流子密度。结果表明:铜在不同条件下表面氧化膜的Mott-schottky曲线线性斜率为负,呈现P型半导体的性质,膜中的多数载流子为空穴。随着铜晶粒度的增大和阳极钝化电位的升高,铜表面钝化膜中的受主密度NA降低;随着介质溶液中的Cl-浓度的升高,钝化膜中的受主密度NA不断增大。     

316L不锈钢在含Cl-高温醋酸溶液中的电化学行为

316L不锈钢试样在空气中放置24 h后在含Cl-醋酸溶液(0.2%KCl,60%的醋酸,85℃)中能自钝化,自腐蚀电位为100 mV;经阴极极化后的试样在实验周期内在含Cl-醋酸溶液中不能自钝化,其自腐蚀电位为(-242±3)mV;经阳极极化形成的钝化膜比在空气中自然形成的钝化膜更致密.测试了空气中钝化24 h以及阴极极化、阳极极化后,试样在醋酸溶液中自腐蚀电位随时间变化的曲线;结合阴极、阳极极化曲线,SEM观察和XPS成分分析,发现Cr是组成钝化膜并增加钝化膜稳定性的重要元素,而Mo是在钝化膜发生活性溶解或者被击穿时于表面富集的元素,可导致该区域电位升高,从而阻止腐蚀发生.初步探讨了316L不锈钢在含Cl-醋酸溶液中的腐蚀电化学行为和点腐蚀发生的机理.     

高压电子铝箔阳极电解扩孔行为

研究发孔铝箔在盐酸和硝酸溶液中的阳极极化行为与扩孔特性的关系。阳极扩孔的基本条件是将发孔箔的内、外表面都控制在钝化状态下。在盐酸溶液中,阳极极化时存在点蚀电位和一个较小的钝化电位区,当扩孔施加的电流密度大于临界点蚀电流密度时,铝箔表面发生二次发孔,导致形成孔蚀族与并孔,腐蚀箔厚度减薄,比电容显著降低。在硝酸溶液中,阳极极化时存在一个宽阔的钝化电位区,因此硝酸扩孔比盐酸扩孔容易控制,不会发生二次发孔。提高盐酸或硝酸浓度与温度均可以增大最大维钝电流密度,即增大扩孔的最大电流密度,提高扩孔的生产效率。     

7050铝合金应力腐蚀敏感性和钝化膜引起的膜致应力随电位变化的一致性

用流变应力差值法测量了不同极化电位下7050铝合金在3.5%NaCl 水溶液（pH=10）腐蚀过程中表面钝化膜形成的拉应力,并用慢应变速率拉伸法测量了不同极化电位下的应力腐蚀敏感性。结果表明:7050铝合金在溶液中自然腐蚀时,表面钝化膜会产生一定的拉应力;阳极极化使表层拉应力明显上升,且随着电位升高应力增大;阴极极化时,当电位E ≥-1100mV时表层拉应力随着电位的升高而降低,当电位≤E-1100mV时拉应力随着电位升高而升高。应力腐蚀敏感性随外加电位变化规律和钝化膜引起的附加拉应力变化完全一致。     

硫酸溶液中铁在过钝化区电极行为

本文应用电位衰减和交流阻抗等电化学方法对H_2SO_4溶液中处于过钝化区的铁的钝化膜的性质进行了研究。发现在钝化-过钝化过渡区域,钝化膜的厚度随着电位的升高而下降。当电位升到1800mV(VS·SCE)以后,钝化膜的厚度不再随电位的变化而变化。对不同电位下的交流阻抗频谱图进行了拟合分析,得到了一些与钝化膜的性质有关的参数。     

Influence of anodic oxidation at low potential on the Corrosion resistance of hafnided zirconium in concentrated sulphuric media

In the context of increasing applications of zirconium in the chemical processing industry the influence of anodic oxidation at low potentials on the corrosion resistance of zirconium has been studied. Experiments were performed in concentrated sulphuric acid media, using electrochemical methods. A transition range of potentials between ?65 and ?50 mV/SCE has been observed. On each side of this transition range hafnided zirconium covered with passive film exhibits different corrosion resistance. Alteration of the passive film, which can be assumed from nuclear microanalysis experiments, has been hypothesized to take account for the modification of the electrochemical behaviour.     

H2S水溶液中的腐蚀与缓蚀作用机理的研究Ⅱ.碳钢在碱性H2S溶液中的阳极钝化及钝化膜破裂

通过极化曲线和交流阻抗谱 (EIS)测定 ,对低碳钢在碱性H2 S溶液中的钝化及钝化膜破裂过程进行了研究。结果表明 ,相同pH值下 ,除氧碱性溶液中加入H2 S,对碳钢的钝化具有一定的促进作用 ;在阳极极化下 ,钝化初期阻抗谱具有两个时间常数 ,表现出不完全钝化的特征 ;随极化电位的升高 ,钝化膜逐渐完整 ,阻抗呈单一容抗弧特征 ,容抗弧半径逐渐增大 ;当极化电位高于 - 690mV时 ,由于电极表面HS 同OH 的竞争吸附和放电作用 ,导致电极表面钝化膜发生酸性溶解 ,并生成硫化物斑点 ,极化电阻显著下降 ,当极化电位高于 - 635mV时 ,钝化膜发生破裂 ,电极表面有大量硫化物生成     

Corrosion behaviour of Nickel-chromium alloys in molten carbonate

The corrosion behaviour of nickel-chromium alloys with chromium contents ranging from 10 to 25% in molten carbonate under reducing gas atmospheres was investigated with electrochemical methods (cyclic voltammetry). The oxide scale was investigated, both after quenching from stationary conditions at fixed potentials and shortly after interrupting a cyclic voltammogram. The composition and the properties of the corrosion products, present as oxide layers, are potential-dependent. At potentials in the range of -1500 to -900 mV the layer consists of lithium chromite (LiCrO₂). For 18- and 25%-chromium alloys a continuous layer is formed. The lithium chromite formed on the 10%-chromium alloy at potentials in the same range does not form a continous oxide layer. At potentials in the range of -700 to +100 mV a continuous oxide layer is formed on all alloys. The corrosion product is a cubic solid solution of nickel oxide (NiO) and lithium chromite. In cyclic voltammetry experiments a hexagonal solid solution of lithium chromite and nickel oxide is formed at -700 mV. The hexagonal solid solution is an intermediate corrosion product between lithium chromite, which is stable at more cathodic potentials and a cubic solid solution of nickel oxide and lithium chromite which is stable at more anodic potentials. On the 10% chromium alloy with a non-continuous oxide scale, a cubic solid solution is formed at -500 mV. At about -300 mV the chromate formation and dissolution starts. For the 18- and 2.5%-chromium alloys, on which a continuous lithium chromite-scale is formed at the open circuit potential, a hexagonal solid solution of lithium chromite and nickel oxide is formed during the anodic scan at -700 mV. When the chromate formation and dissolution starts at about -300 mV, the chromium content of the scale decreases, the nickel content increases and the hexagonal solid solution becomes a cubic solid solution. The cathodic scan is very similar to the cathodic scan of pure nickel. During the cathodic scan the oxide scale mainly consists of a nickel-rich cubic solid solution of nickel oxide and lithium chromite because chromium has dissolved as chromate ions during the preceding anodic scan. The reactions are essentially the same as those on pure nickel [1, 2, 3].     

Uniformity of passive films formed on ferrite and martensite by different inorganic inhibitors

A comparison of uniformity of passive films formed on ferrite and martensite by three kinds of inorganic inhibitors, chromate, bicarbonate and nitrite, has been made by anodic polarization curve and AC impedance measurements. It was found, by anodic polarization curve analyses, that there was different pitting susceptibility of passive films formed on ferrite and martensite by chromate or bicarbonate. In the solution containing chloride ions, the broken potential of the passive film formed on ferrite by chromate or bicarbonate was more negative than that on martensite. However, the passive films formed on both ferrite and martensite by nitrite had similar pitting susceptibility. Their broken potentials were almost the same. The difference in pitting susceptibility of the passive films was explained by Mott-Schottky analyses. It was found that the passive film formed on ferrite by chromate or bicarbonate had a higher donor concentration than the passive film on martensite. The passive films with higher donor concentrations were more sensitive to chloride ions. However, the passive films formed on both ferrite and martensite by nitrite had the same donor concentration. A uniform passive film can be formed on a martensite mild steel with ferrite bands by nitrite.     

Effects of an applied magnetic field on the dissolution and passivation of iron in sulphuric acid

The effects of an applied magnetic field (MF) on the electrochemical state, anodic dissolution and passivation of iron in sulphuric acid solution were studied by potentiodynamic scanning polarisation measurements, potentiostatic polarisation measurements and scanning electron microscopy observation. The magnetic field reduced the fractional surface film coverage on the electrode by enhancing the film dissolution process. This made the electrode prone to active dissolution. With increasing applied potentials the magnetic field accelerated the anodic dissolution at relatively low potentials, changed the oscillation or passivation to permanent active dissolution at intermediate potentials, and maintained the passive state at high potentials. Potentials for the onset of passivation moved in the noble direction when the magnetic field was imposed. An electrode kinetics formulation for the effects of the magnetic field on the dissolution and passivation is proposed. In the presence of a magnetic field and at specific anodic potentials, scalloping occurred due to accelerated localized dissolution. The scalloping areas were on both sides of the electrode and oriented parallel to the direction of the earth’s gravitation field. The ratios of the scalloping area caused by a 0.4 T magnetic field on the whole electrode surface were 0.69 (at 200 mV), 0.66 (at 350 mV) and 0.75 (at 400 mV), respectively. In contrast, uniform electrode surfaces were observed at these anodic potentials in the absence of the magnetic field. Uneven dissolution of iron in the presence of a magnetic field was related to the relative configuration between the magnetic field direction and the electrode surface and also to the special concentration gradient of reactive species at the electrode circumferential area.     

316L不锈钢、690合金在氢氧化钠溶液中的电化学性能

采用动电位极化、电化学阻抗和电容测量等方法研究了316L、690合金在NaOH溶液中的电化学行为及生成钝化膜的半导体性质.在NaOH溶液中,316L不锈钢存在明显的钝化区间;316L不锈钢、690合金在NaOH溶液中电化学阻抗谱的阻抗模值相近.动电位电化学阻抗谱(DEIS)表明,随扫描电位正移,钝化膜的阻抗在测试溶液中...     

Corrosion behaviour of Nickel-aluminium alloys in molten carbonate

The corrosion behaviour of nickel-aluminium alloys with aluminium contents of 2-50%, in molten carbonate has been investigated with electrochemical techniques in combination with post-test analysis of quenched specimens. For the 2 to 10% aluminium alloys a type of aluminium oxide is formed along the grain boundaries of the base metal at potentials of -1100 and -900 mV. At potentials of -700 nmV and more anodic an outer oxide scale is formed and also aluminium oxide formation takes place along the grain boundaries. The oxide scale contained nickel, aluminium and oxygen. The only corrosion product that could he detected by X-ray diffraction on specimens quenched after polarisation at -700 mV or more anodic is NiO; no type of aluminium oxide could be detected, probably due to the small amount of aluminium oxide formed. For the 20% aluminium alloy a type of aluminium oxide is formed along the grain boundaries at -1100 and -900 mV. After longer polarisation times also the aluminium in the interior of the grains is oxidised, which results in a two-layer microstructure: an outer layer of pure nickel, and an inner layer that is a honeycomb network of nickel filled with aluminium, oxygen and nickel, while high amounts of aluminium and oxygen could be detected along the grain boundaries. The amount of corrosion product was too small to be detected by X-ray diffraction. At potentials of -700 mV and more anodic, an oxide scale of irregular thickness is formed, but no oxide could be observed along the grain boundaries. The only corrosion product detected by X-ray diffraction on specimens quenched after polarisation at potentials in this range is nickel oxide. On the 50% aluminium alloy a continuous oxide layer is formed at all potentials. The only corrosion product formed at all potentials is α-LiAlO₂; the stable form of LiAlO₂ is γ-LiAlO₂. α-LiAlO₂ is probably an intermediate product that is slowly transformed to γ-LiAlO₂. The oxide layer provides good protection against further corrosion of the base material. The quasi-stationary polarisation curves are very similar to those of pure nickel, because no protective oxide scales are formed on the 2 to 20% aluminium alloys during preconditioning at -1100 mV.     

Untersuchungen zum Einfluß von Sulfid- und Sulfationen auf die Korrosion des Eisens in alkalischer Lösung

Investigation into the influence of sulfide and sulfate ions on the corrosion of iron in alcaline solution The corrosion behaviour of Armco iron as well as that of a technical high-strength steel was investigated in sulphide - and sulphate-containing electrolytes of pH ～ 12.6. Current density - potential curves show that iron, after successful passivation, remains passive and protected against corrosion in a solution saturated with CaS, CaSO₄ and Ca(OH)₂ at potentials up to 800 mV(EH). Passivation experiments conducted by changing from the active region to various anodic potentials yielded a critical potential region around 300 mV(EH), above which corrosion appeared. Up to E_H = 200 mV complete passivation was observed. The same critical potential region was observed in experiments of repassivation after mechanical damaging of a protective passive layer. Additional tensile stresses of 85%· σ_0,2 caused no stress corrosion cracking at a potential of 500 mV(EH). After damaging the passive layer, through scratching of the stressed wires fracture occured at and above potentials of 300 mV(EH). At 200 mV(EH) repassivation was observed even under tensile load. In a sulphate-free Na₂S/Ca(OH)₂ solution of the same sulphide ion concentration no stress corrosion cracking of the samples occured at any potential up to 800 mV(EH) even after scratching the steel samples. The observed stress corrosion in sulphide - and sulphate-containing electrolytes is to be ascribed to the action of sulphate and not to sulphide ions.