用放射性示踪技术研究黄铜应力腐蚀过程的脱锌

用测试~(64)Cu和~(65)Zn同位素γ射线的放射性示踪技术研究了在慢应变速率动态拉伸条件下70/30黄铜在室温1M NaNO_2溶液中,-0.1V(SCE)下的应力腐蚀开裂(SCC)和脱锌行为。结果说明,包含铜在内的局部阳极溶解是该体系SCC的根本原因,而大量的脱锌则加剧了开裂敏感性。在应力达到最高拉伸应力(σ_(UTS))之前的裂纹稳态扩展阶段,脱锌系数最大,此阶段之后由于铜的溶解比例增大,脱锌系数相对较低。在稳态扩展阶段,裂纹尖端导致最大脱锌系数的应变速率估计约为初始应变速率的4倍左右。按择优溶解的体扩散模型算得SCC过程中锌的扩散系数可达10~(-11)cm~2/s数量级以上。文中还讨论了黄铜在亚硝酸盐溶液中SCC过程的脱锌机理。     

阳极极化状态下铁电极的交流阻抗

研究了铁电极在中性Na_2SO_4溶液中恒电位阳极极化下。和在不同pH的H_2SO_4/Na_2SO_4溶液中腐蚀电位下的交流阻抗特性。当pH>3.5时,铁电极的界面电容急剧增大至10~3μF/cm~2数量级。而铁电极在中性Na_2SO_4溶液中的界面电容为铁电极上覆盖的Fe(OH)2的电容。通过恒电位阳极极化状态铁电极的高频和低频部份的阻抗特性分析,建立了阳极极化状态铁电极的等效电路。用交流阻抗计算了极化电流密度,其值与同样条件下测得的稳态电流密度相等,说明阳极极化状态下交流阻抗测定的适用性。     

电位对70/30黄铜在1N NaNO_2中的脱锌系数及应力腐蚀开裂敏感性的影响

用原子吸收光谱测定了在慢应变速率的应力腐蚀试验条件下,70/30黄铜在1当量亚硝酸钠水溶液中,电位范围—0.1～ 0.1V(SCE)内的脱锌系数。结果表明,所有试验都发生严重脱锌,但是,电位对脱锌系数和应力腐蚀开裂敏感性的作用影响相反:提高电位加速裂纹扩展,却降低了脱锌系数。应变速率的加快对增加脱锌系数的作用也随电位提高而减弱。在阳极溶解模型的基础上,采用快速应变电极测试的数据,理论计算得出的脱锌系数随电位和应变速率变化的趋势与实验结果相似。从而说明,尽管黄铜总的溶解速率随电位提高而增加(黄铜中的锌亦如此),加剧了开裂敏性,但是锌、铜溶解相对比率中铜溶解部份的递增造成脱锌系数下降。文章进一步讨论了与黄铜应力腐蚀机理有关的本结果涵义。     

α黄铜选择性溶解的研究

采用恒电流E-t曲线与旋转盘环电极方法研究了α黄铜(Cu32Zn)在酸性Na2SO4和HNO3稀溶液中的阳极溶解行为,得到的典型E-t曲线上存在几个特征区,证明在较低电流密度条件下的初始阶段只存在Zn的选择性溶解。用恒电位法研究了Cu32Zn选择性溶解过程,得到了按抛物线衰减的暂态扩散曲线,由i-t-1/2直线关系求得了不同介质中Cu32Zn中Zn的固相扩散系数D在10-16～10-13cm2·s-1数量级,发现中性介质中测出的D值比酸性介质中要大两个数量级。     

磁场对Cu／NaCl体系表现Tafel区阳极溶解的作用

采用线性电位扫描化曲线测试,以及恒电位极化下磁场扰动法研究了磁场对铜在氯钠溶液中的阳极溶解的作用,在阳极表观Tafel区,无磁场时恒电位极然后外加磁场使阳极电流密度增大,有磁场时恒电位极化然后撤去磁场使阳极电流密度减小,磁场通过加速电极溶液界面的传质过程而加速阳极溶解,由于Cu/NaCl与Fe/H2SO4体系阳极Tefel区速率控制步骤不同,会导致不同的磁场效应作用。     

海水管路黄铜焊接接头在人工海水中的电化学阻抗谱

利用扫描电镜(SEM)、阳极极化与电化学阻抗谱(EIS)试验方法,研究了紫铜管路中的黄铜焊缝在人工海水中的腐蚀特性。结果表明,在Tafel区,黄铜焊缝以CuCl2-络合离子和Zn2 溶解,并且CuCl2-和Zn2 的扩散是该溶解过程的控制步骤;当电极电位极化到-0.01～ 0.31V时,难溶物Cu2O、CuCl、ZnO和Zn(OH)2ZnCl2附着在电极表面阻碍电极极化,因而在EIS谱图上出现2个容抗弧;电极电位超过 0.31V后,难溶物开始溶解至 0.57V完全溶解,这时电极反应以脱锌腐蚀为主,电极过程为Zn2 离子向溶液扩散控制。     

铝-锌-铟-硅牺牲阳极材料电化学性能的研究

在同样条件下比较了铝-锌-铟-硅、铝-锌-铟-镉、铝-锌-铟-锡和三元锌四种阳极的化学特性,以确定铝-锌-铟-硅阳极性能的优劣。试验介质用大连老虎滩的海水和泥沙,配制成10％、40％,70％和100％的海水、淡海水和海泥。主要测定了阳极的自放电时间—电位曲线、极化特性曲线,静态充电曲线和电流效率。试验共进行240小时,自放电时间电位曲线的阳极电流密度为0.5mA/cm~2,电流效率的阳极电流密度为1mA/cm~2,静态充电通以电流密度为2.6mA/cm~3的恒定电流,极化特性曲线变化电流密度从0.5mA/cm~2至0,再增至1mA/cm~2,最后再至0.5mA/cm~2时,观察电位随电流密度的变化规律。     

碱性介质中铜镍合金及铜电极的光电化学研究

用动电位伏安法和光电化学方法对铜镍合金(7％Ni 93％Cu)和铜电极在碱性介质中的电化学行为进行了研究。铜镍合金电极的阳极氧化膜呈p型光电响应,光电响应来自电极表面的Cu_2O膜,其厚度大于纯铜电极的Cu_2O膜。铜电极在碱性Na_2SO_4溶液中电位正向扫描时的光响应呈p型,点蚀电位以后光响应从p型转为n型。     

铝在氯化物溶液中的交流阻抗

用相敏检波法测定了铝在氯化物溶液中当用约300μA/cm~2～30mA/cm~2电流密度阳极极化时的表面阻抗。结果表明lgRf(法拉第阻抗)与lgi(阳极极化电流密度)成线性长系,电容C与i成线性关系;证实了铝阳极溶解时活性溶解区的面积是外加阳极极化电流的线性函数,真实电流密度实际上并无变化,因此电位也无变化。     

B10铜镍合金在NaCl溶液中腐蚀行为的研究

研究了BFe10-1-1铜镍合金在0.5mol/L NaCl溶液中的选择性腐蚀行为,测其在不同pH值的试验溶液中的阳极极化曲线,并选择一定电化学条件下进行恒电位腐蚀。通过对腐蚀后溶液中的Cu2 和Ni2 含量的分析和对试样断面的微区成分分析,了解不同条件下的BFe10-1-1铜镍合金的选择性腐蚀规律。试验结果表明,BFe10-1-1铜镍合金的选择性腐蚀取决于腐蚀介质的酸碱度及腐蚀电位等电化学条件。在碱性溶液中的耐蚀性比其在酸性溶液中要好,在酸性和弱碱性溶液中脱镍,在强碱性溶液中低电位下脱铜,高电位下脱镍。     

Corrosion of cold-deformed brass in acid sulphate solution

The corrosion behaviour and the dezincification process of cold-deformed CuZn-42 brass were tested in an acid sulphate solution at pH-value 2 with additional chloride and copper(II) ions by use of the linear polarization method.The measured corrosion potential and densities of corrosion currents were observed as characteristics of the dezincification process and the corrosion resistance of tested samples of cold-deformed CuZn-42 brass. The results obtained have shown that pH-value 2 of the tested solutions and increased concentrations of copper(II) ions result in increased values of densities of corrosion currents of the tested brass samples, as a result of selective zinc dissolution and the individual dissolution of zinc and copper including the process of anodic oxidation. The tested concentrations of chloride ions in certain conditions have an inhibiting effect, whereas in the other conditions they act as distinctive activators of brass corrosion. The lowest values of corrosion currents are present in the brass samples with the highest deformation degree at 80%. The process of dezincification and anode dissolution of cold deformed brass samples were developed in the whole range of tested potentials.     

(α+β)两相黄铜脱锌机理研究(Ⅱ)

本文在前文基础上,用旋转圆盘-圆环电极进一步研究了(α+β)两相黄铜HPb59-1在不含Cu~+的去氧酸性氯化钠溶液中阳极溶解时的脱锌行为。根据盘-环电极收集系数与时间,转速、盘电流的关系,再次证实该黄铜在实验条件下的脱锌过程遵循溶解-再沉积机理,并求出了铜再沉积反应的速度常数为2.1×10~(-2)cm/sec。     

A study on the 65‐35 brass corrosion inhibitor

The influence of new inhibitor namely 1,3‐bis‐diethylamino‐propan‐2‐ol (DEAP) on the dezincification corrosion of 65‐35 brass in simulated atmospheric water was studied by potentiostatic current transient measurement, solution analysis and surface evaluation techniques. Potentiostatic current transient results showed that the investigated inhibitor can effectively inhibit the chemical dissolution of brass in simulated atmospheric water. Solution analysis revealed that the weigh loss of brass electrode remarkably decreased in the presence of DEAP, changing from 7.375 × 10^?3 mg (blank) to 9.567 × 10^?4 mg (10^?2 M). The scanning electron microscope (SEM) and electron probe microanalyzer (EPMA) measurements showed that DEAP may better adsorb to zinc component than to copper component, inhibiting the dezincification of brass in solution by a mixed complex film of Zn(II)‐DEAP and Cu(I)‐DEAP. The nature of the inhibited film was analyzed by an X‐ray photoelectron spectroscope (XPS) analyzer.     

电解质对锌在薄层液膜下腐蚀规律的影响

设计了一套适合于研究金属材料在薄层液膜下腐蚀的三电极电化学测量电池。Cl^-浓度的增大，促进了Zn在大量溶液中的阳极反应，降低了传递电阻和自腐蚀电位，从而导致腐蚀速率增大。在0.01mol/L的NaCl溶液中，随着液膜厚度的减小，传递电阻增大，腐蚀速度降低。在同浓度、不同电解质的大量溶液中，Na2SO4溶液对Zn的腐蚀最严重，其次是NaN03，腐蚀最轻的是NaCl；而在薄层液膜下，对Zn的腐蚀作用最明显的是NaCl；其次是Na2SO4；再次是NaN03，最轻的是Na2CO3。     

Galvanic compatibility of corrosion protective coatings with AA7075 aluminum alloy

The galvanic compatibility of aerospace aluminum alloy AA7075 with cadmium (Cd), zinc (Zn), and zinc–cobalt–iron (Zn–Co–Fe, 32–37%Co and 1%Fe) alloys was investigated. A comparison of open circuit potential [OCP vs. saturated calomel electrode (SCE)] measurements in 0.6 mM NaCl showed that all coatings would act anodically to AA7075 with an exception of Zn–Co–Fe (37%Co + 1%Fe) alloy which was electropositive to AA7075. During the zero resistance ammetry (ZRA) measurement in 0.6 M NaCl electrolyte the coupled OCP and current density were measured during 7 days of immersion and both Zn and Cd acted anodic and thus sacrificial to AA7075. Galvanic coupling of AA7075 with (37%Co + 1%Fe) Zn–Co–Fe alloy resulted in the consequent dissolution of the AA7075 aluminum alloy. In contrast, Zn–Co–Fe (32%Co + 1%Fe) alloy was found to be anodic to AA7075 during the first 26 h of immersion but after dezincification and cobalt enrichment at the surface became cathodic to the AA7075 aluminum alloy. During coupling with Zn, some pitting was also observed on AA7075.     

The stress-assisted dezincification of 70/30 brass in ammonia

Zinc and copper losses from 70/30 brass specimens tensile loaded to various stress levels and exposed to 10 N NH₄OH were estimated at different time intervals by atomic absorption spectroscopic analysis of the corrodent. Dissolution of each element was found to be accelerated with increasing tensile stresses. The preferential dissolution of Zn was also found to increase with stress and a maximum in the dezincification occurred at about 105 MPa. Corrosion of the brass as a whole, however, increased monotonically with stress. Applied stresses altered the open circuit potential of the brass by a maximum of ±10⁻¹ mV MPa-1, and its potentiostatic polarization curve was shifted to higher current densities. The depth of dezincification for short intervals calculated from the present results showed that dezincification could be a viable mechanism for transgranular stress corrosion cracking of brasses.     

New thermogalvanic method determines the conditions which cause dezincification of admiralty brass in field service

A newly developed laboratory test method based on thermogalvanic currents realistically simulates the dezincification of admiraly brass in fresh or sea water. It is especially useful for studying the dezincification of brass heat exchanger tubes.The method uses an internally heated tube that is exposed to a test solution while being galvanically coupled to a relatively large colder piece of the same metal. The tube is thermally insulated in such a way that hot spots and boiling are induced on its surface. The temperature difference between the hot tube and the colder piece of metal produces a thermogalvanic action that results in current densities up to 0.16 mA cm^?2. The electrode potential of the heated tube is more negative than when the tube is cold. Under these conditions, dezincification of inhibited admiralty tube occurred within 72 h in fresh water and much sooner in a 0.5% solution of sodium chloride.Under these test conditions, two types of dezincification were noted, depending on the kind of boiling and the intensity of the associated thermogalvanic current produced on the surface of the tube; localized film boiling caused a plug-type dezincification with strong evidence for the redeposition of copper, whereas localized nucleate boiling causes a layer-type dezincification with strong evidence for dissolution of the zinc. Very low water velocities, high process side temperatures, low pH or presence of a water conditioning treatment resulting in non-scaling water, high solution conductivity, and the absence of waterside corrosion inhibitors are factors which lead to dezincification in field service.     

PbO_2/Ti电极在不同盐份海水中的电化学行为和应用

测定了 PbO_2/Ti 电极在10%海水、天然海水、0.5NNa_2SO_4和5MNaCl 溶液中,温度25℃时的阳极极化曲线。在高电流密度范围内,它比 Pt/Ti 电极具有较低的氯和氧的过电位。该电极在上述介质中的消耗率比 Pt/Ti 阳极大,但远小于 Pb～2%Ag 阳极。这种电极已应用于阴极保护系统和次氯酸钠发生器中。