金属氧化物在熔融Na_2SO_4中的溶解行为

建立了高温Pourbaix型Na-M-S-O系热力学相图,总结了近年来金属氧化物在熔融Na_2SO_4中的溶解度的研究结果,并用高温Na-M-S-O系相图予以解释,还给出了有关金属溶解形式在熔融Na_2SO_4中的活度系数。基于金属氧化物在熔融Na_2SO_4中的溶解行为的研究结果,讨论了由熔融Na_2SO_4引起的热腐蚀的盐溶模型。     

Phase diagrams of Li2MoO4-Na2MoO4 and Na2MoO4-K2MoO4 systems

The phase diagrams of the Li2MoO4-Na2MoO4 and Na2MoO4-K2MoO4 systems have been reassessed using differential thermal analysis together with high-temperature and room-temperature X-ray diffraction analysis. The results showed that the compound Li2MoO4.6Na2MoO4 did not exist; however, it confirmed the existence of the compound Li2MoO4.3Na2MoO4 in the Li2MoO4-Na2MoO4 systen＇ls. With regard to the system of Na2MoO4-K2MoO4, we could not confirm the results reported by Bukhanova who claimed that the system was eutectic type with 1：1 and 1：2 intermediate compounds, refuting the statement of Amadori who thought there was an apparent phase boundary at high temperature in α-solid solution region of the Na2MoO4-K2MoO4 binary system. The revised phase diagrams of these systems are illustrated in this article. These experimental results are in agreement with the computerized prediction using the support vector machine-atomic parameter method for the assessment of phase diagrams.     

表面有Na2SO4沉积时铁基合金的低温热腐蚀行为

研究了工业纯铁、Fe-Cr和Fe-Al合金表面有Na_2SO_4沉积时于O_2/SO_2/SO_3气氛中的低温热腐蚀行为。测定腐蚀动力学曲线,研究温度、气体组成及合金元素对腐蚀动力学的影响,并对腐蚀产物的形貌和组成进行观察与分析。结果表明,在工业纯铁、Fe-Cr和Fe-Al合金的低温热腐蚀过程中都发生金属表面致密氧化层的快速成长和疏松的Fe_2O_3在盐膜中的沉积,且前者对腐蚀的贡献居大。以实验结果为依据,初步提出了电化学机理模型,并用以阐述铁基合金低温热腐蚀过程。     

硅锌矿在(NH_4)_2SO_4-NH_3-H_2O体系中的浸出机理

对硅锌矿在(NH4)2SO4-NH3-H2O体系中的浸出行为进行了系统研究,揭示浸出反应机理,阐明其难以浸出的内在原因。结果表明:硅锌矿浸出反应方程为Zn2SiO4(s)+(2i-4)NH3(aq)+4NH4+=2[Zn(NH3)i]2++SiO2(s)+2H2O(l),i=1～4。浸出中,硅锌矿中的硅溶解进入溶液,再以无定形SiO2形态从溶液中析出。SiO2在(NH4)2SO4-NH3-H2O体系中的溶解度很低,仅略高于0.3 g/L,而其从溶液中的析出速度非常缓慢,是硅锌矿在该体系中难以浸出的主要原因。当液固质量比从5提高至500时,锌浸出率将从2.72%提高至84.15%。     

CuNiCrAl合金在H2SO4溶液中的腐蚀行为

借助金相、X射线衍射(XRD)、扫描电镜(SEM/EDX)及X射线荧光光谱仪研究了CuNiCrAl合金在H2SO4溶液中的腐蚀行为.结果表明CuNiCrAl合金在低温H2SO4溶液中,合金中的Cu相较易腐蚀;当H2SO4溶液浓度和温度达到一定值时,合金出现脱铬腐蚀现象,溶液的浓度和温度越高,脱铬倾向越大,且溶液添加NaCl能促进合金的脱铬腐蚀,还对CuNiCrAl合金的脱铬机制进行了探讨.     

SO2-4 ,PO3 4- 对曼尼希碱酸化缓蚀剂缓蚀性能的影响

目的：研究废酸液中介质离子对曼尼希碱酸化缓蚀剂缓蚀性能的影响,以解决碳钢在酸液中的腐蚀问题。方法采用静态失重法、极化曲线、扫描电镜及能谱分析法,研究SO2-4,PO3-4对曼尼希碱型酸化缓蚀剂缓蚀性能的影响,并探究其作用机理。结果在10%(质量分数)盐酸、0.1%(质量分数)曼尼希碱的缓蚀介质中,随SO2-4质量分数的增大,腐蚀电流密度由2.81μA/cm2增加至7.32μA/cm2,腐蚀速率显著增大,缓蚀效果变弱;随PO3-4质量分数的增加,腐蚀电流密度由2.81μA/cm2减小至2.41μA/cm2,腐蚀速率减小,缓蚀效果变强。结论 SO2-4会通过钢铁表面已经形成的吸附膜上的细孔和缺陷渗入膜内,使膜发生开裂,从而侵蚀和破坏已经形成的吸附膜,抑制缓蚀剂的缓蚀效果;PO3-4与腐蚀产物Fe3+络合并在钢材表面形成一层致密的保护层,使缓蚀剂形成的吸附膜更加致密,阻止腐蚀性介质与金属表面接触,同时增加对离子或溶解氧的扩散阻力,提高缓蚀剂的缓蚀效果。     

Preparation of high-purity indium by electrorefining

The application of indium requires high purity indium as material, and the high purity indium has been prepared by electrorefining. The selection and preparation of electrolyte in electrorefining indium were investigated,and the effect of component of electrolytic solution on electrolytic refining was also studied. Compared with electro-lyte of InCl3-HCl, electrolyte of In2(SO4)3-H2 SO4 has higher stability and lower corrosivity, electrolytic solution can be heated at low temperature, and bath is open and simple, which makes operation more convenient. The results show that the voltage can be kept at 0. 3-0.5 V, and the content of indium can exceed 99. 999% when the contentof indium(Ⅲ) ion and sodium chloride are 80-120 g/L. The bench-scale test of electrolysis was carried out, and the product of indium reaches the national standard of 99. 999% high purity indium.     

用丝束电极研究SO4^2-对纯铝缝隙腐蚀的影响

采用动电位极化和丝束电极技术测量了纯铝在2mol／L NaCl和2mol／L NaCl＋0．8mol／L Na2SO4溶液中的极化曲线、缝隙内外的自腐蚀电位和电化学阻抗分布，研究了SO4^2-对铝缝隙腐蚀的影响。结果表明，在NaCl溶液中，缝隙内的铝为阳极、缝隙外为阴极；随浸泡时间增加，腐蚀不均匀性增加。加入Na2SO4后，减小了缝隙内外腐蚀电位差，显著降低了铝的腐蚀速度。Na2SO4是中性溶液中铝的吸附型缓蚀剂，延缓了缝隙腐蚀的发生。     

制取活性锌粉的Zn(Ⅱ)-NH3·H2O-(NH4)2SO4体系电解法

研究了在Zn(Ⅱ)-NH3*H2O-(NH4)2SO4体系中电解制取活性锌粉新工艺.结果表明在常温下, 电流效率高达88.19%, 每吨产品能耗为3254.37kW*h, 其产品质量符合GB6890-86标准; 活性锌粉杂质含量低, 锌含量≥98.78%, 有效锌含量≥96%, 锌的总回收率为97.97% .该法与以金属锌为原料的蒸馏法、雾化法相比较, 成本大幅度降低.     

Effects of NaCl and NH4Cl on the initial atmospheric corrosion of zinc

Effects of NaCl and NH₄Cl on the initial atmospheric corrosion of zinc were investigated via quartz crystal microbalance (QCM) in laboratory at 80% RH and 25 °C. The results show that both NaCl and NH₄Cl can accelerate the initial atmospheric corrosion of zinc. The combined effect of NaCl and NH₄Cl on the corrosion of zinc is greater than that caused by NH₄Cl and less than that caused by NaCl. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy and electron dispersion X-ray analysis (SEM/EDAX) were used to characterize the corrosion products of zinc. (NH₄)₂ZnCl₄, Zn₅(OH)₈Cl₂ · H₂O and ZnO present on zinc surface in the presence of NH₄Cl while Zn₅(OH)₈Cl₂ · H₂O and ZnO are the dominant corrosion products on NaCl-treated zinc surface. Probable mechanisms are presented to explain the experimental results.     

Effects of NaCl and SO2 on the initial atmospheric corrosion of zinc

The influence of NaCl deposition on the corrosion of zinc in atmospheres with and without SO₂ was studied via quartz crystal microbalance. Regularity of the initial corrosion of zinc under these conditions was analyzed. The results show that NaCl can accelerate the corrosion of zinc. Mass gain of zinc increases with the exposure time, which can be correlated by using exponential decay function. The relationship between mass gain and amount of NaCl deposition is well linear at any time in air containing 1 ppm SO₂, but follows quadratic function in air without SO₂. More amount of NaCl deposition will slow down the corrosion to some extent after exposure for certain time in the presence of SO₂. The combined effect of NaCl and SO₂ on the corrosion of zinc is greater than that caused by each single component. Fourier transform infrared spectroscopy and X-ray diffraction were used to characterize the corrosion products of zinc. In the absence of SO₂, simonkolleite, Zn₅(OH)₈Cl₂·H₂O and zincite, ZnO are the dominant corrosion products, while zinc hydroxysulfate (Zn₄SO₄(OH)₆·3H₂O), zinc chloride sulfate hydroxide hydrate (Zn₁₂(SO₄)₃Cl₃·(OH)₁₅·5H₂O) and simonkolleite dominate in the presence of SO₂. Brief discussion on the mechanisms of atmospheric corrosion under these conditions was introduced.     

Comparison of corrosion behaviour of zinc in NaCl and in NaOH solutions. Part I: Corrosion layer characterization

The corrosion layer formed on zinc sample in 0.6 M NaCl and 0.5 M NaOH solution under ambient conditions has been investigated. The corrosion layer morphology was analyzed using scanning electron microscopy (SEM). X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to characterize the corrosion products of zinc. The thickness evolution of the corrosion layer was investigated by glow discharge optical emission spectroscopy (GDEOS). The corrosion layer formed in 0.5 M NaOH solution appeared more compact than that formed in 0.6 M NaCl solution. Zinc hydroxide chloride (Zn₅(OH)₈Cl₂·2H₂O) and zinc hydroxide carbonate (Zn₅(CO₃)₂(OH)₆) were formed on zinc surface in 0.6 M NaCl solution while in 0.5 M NaOH solution, zinc oxide (ZnO), zinc hydroxide (Zn(OH)₂) and zinc hydroxide carbonate (Zn₅(OH)₆(CO₃)₂·H₂O) were detected. Probable mechanisms of zinc corrosion products formation are presented.     

Corrosion product formation on Zn55Al coated steel upon exposure in a marine atmosphere

The formation of corrosion products on Zn55Al coated steel has been investigated upon field exposures in a marine environment. The corrosion products consisted mainly of zinc aluminium hydroxy carbonate, Zn_0.71Al_0.29(OH)₂(CO₃)_0.145·xH₂O, zinc chloro sulfate (NaZn₄(SO₄)Cl(OH)₆·6H₂O), zinc hydroxy chloride, Zn₅(OH)₈Cl₂·H₂O and zinc hydroxy carbonate, Zn₅(OH)₆(CO₃)₂ were the first three phases were formed initially while zinc hydroxy carbonate Zn₅(OH)₆(CO₃)₂ was formed after prolonged exposure in more corrosive conditions. The initial corrosion product formation was due to selective corrosion of the zinc rich interdendritic areas of the coating resulting in a mixture of zinc and zinc aluminium corrosion products.     

Influence of anions on the formation and structure of artificial zinc rusts

To simulate the atmospheric corrosion of steels galvanized with Zn under different conditions, artificial zinc rusts of basic zinc salt (BZS) were prepared by hydrolyzing ZnO particles in aqueous solutions including ZnCl₂, ZnSO₄ and Zn(NO₃)₂. In ZnCl₂–ZnSO₄, ZnSO₄–Zn(NO₃)₂ and ZnCl₂–Zn(NO₃)₂–ZnSO₄ systems, zinc hydroxysulfate (Zn₄(OH)₆(SO₄)·nH₂O) was formed while zinc hydroxychloride (Zn₅(OH)₈Cl₂·H₂O) was generated in ZnCl₂–Zn(NO₃)₂ system. Zinc hydroxynitrate (Zn₅(OH)₈(NO₃)₂·2H₂O) was yielded in only Zn(NO₃)₂ system. All the formed artificial zinc rusts were hexagonal plate particles. These results suggest that SO_x is the most effective corrosive gas on the formation of BZS rusts on galvanized steel.     

The effect of synthetic zinc corrosion products on corrosion of electrogalvanized steel. II. Zinc reactivity and galvanic coupling zinc/steel in presence of zinc corrosion products

The reactivity of zinc under synthetic zinc patinas and the galvanic coupling in steel/patina/Zn are studied. Zn₅(OH)₆(CO₃)₂ and Na₂Zn₃(CO₃)₄⋅3H₂O inhibit zinc anodic dissolution in NaCl, while Zn₅(OH)₈Cl₂ H₂O and Zn₄(OH)₆SO₄ nH₂O do not. The galvanic current in steel/patina/NaCl/Zn is smaller as compared to steel/NaCl/Zn. The inhibiting effect decreases with time for Na₂Zn₃(CO₃)₄⋅3H₂O or Zn₄(OH)₆SO₄ nH₂O due to the transformation into Zn(OH)₂. In NaHCO₃, the polarity between zinc and steel can reverse. The effect of confinement on the cathodic current is stronger than the initial effect of patina which is explained by the instability of the patinas under rapid pH-increase.     

Zur Korrosion von unlegiertem Stahl und Aluminium in wäßrigen Lösungen von Ammoniak und Kohlensäure — 1. Mitteilung: Korrosionsprodukte

Corrosion of unalloyed steel and aluminium in aqueous solution of ammonia and carbonic acid-1. Communication:Corrosion products Two new corrosion products were detected in testing of pure iron, rimming unalloyed steel, aluminium (99,9) and Al-Mg 1,5 in aerated aequous solutions of 130 g/l NH₃ and 80/l Co₂ at 60°. On iron and unalloyed steel the compound (NH₄)₂Fe₂(OH)₄(CO)₃ · H₂O was formed and on aluminium or Al-Mg 1,5 NH₄Al(OH)₂CO₃ · H₂. Both compounds were synthesized and compared by X-ray diffraction, IR spectrum, thermoanalysis, and chemical analysis with published literature. For NH₄Al(OH)₂CO₃ · H₂O the unit cell was calculated which changes somewhat with for the corrosion product are a = 6,64 Å; b = 11,99 Å; c = 5,76 Å. Orthorhombic lattice, aspect C*c*, or (a*) = 13.29 Å; C* = 11,99 Å (hexagonal lattice, pseudohexagonal?). The measured density = 2.03 g · the calculated 2,29 g · cm for Z = 4. The infrared spectrum was partly newly coordinated. Between aluminium metal and NH₄Al(OH)₂CO₃H₂O epitaxial relations are possible, which could explain the higher resistance against corrosion in comparison with steel in the test solution.     

In situ studies of the corrosion during drying of confined zinc surfaces

The corrosion process during the drying out of zinc surfaces confined in crevices was studied using real time photograpy and in situ FTIR microspectroscopy. A pH‐indicator was used to visualise differences in the pH during the drying process. The distribution and the composition of the corrosion products after several wetting and drying cycles were studied with FTIR microspectroscopy and SEM‐EDS. An area with high pH formed during the drying process at the border of the electrolyte, with a zone of white corrosion products that contained zinc hydroxycarbonate in the electrolyte inside this area. A differential aeration cell is present at the border of the electrolyte, and the cathodic oxygen reduction reaction takes place close to the border of the electrolyte during the drying process. The corrosion attack and the distribution and composition of the corrosion products on the surface depend strongly on the drying process of the surface. The corrosion attack of confined surfaces was localised, with a significantly higher corrosion attack in some areas. Outside the drying front a thin layer of electrolyte formed as a result of surface tension driven flow of electrolyte from the electrolyte border. This effect was attributed to the alkaline pH of the electrolyte due to the oxygen reduction reaction at the border. A galvanic element was formed between the local cathodes in the area outside the drying front and the anode in the area with bulk electrolyte. The main corrosion products detected after several wet dry cycles were ZnO, Zn₅(OH)₆(CO₃)₂ and Zn₅(OH)₈Cl₂ · H₂O, but Na₂CO₃ · 10H₂O was also detected. The corrosion products were non‐homogeneously distributed on the surface and the distribution was related to the anodic and cathodic processes that took place in different regions on the surface during the corrosion process.     

Corrosion Products Formed on Copper exposed to humid SO2-containing atmospheres

X-ray diffraction analyses have been performed on samples of electrolytic copper (min. 99,9% Cu) exposed to humid atmoshperes at SO₂-supplies of 10 and 100μg SO₂ per cm² surface area per hour (10 and 100 ppm SO₂. respectively). During the SO₂ -exposures copper (II) sulphate (CuSO₄ · 5 H₂O) were the only crystalline phases formed in detectable amounts. Interruption of the SO₂- supply resulted in the formation of copper (I) oxide and antlerite (CuSO₄) · 2Cu (OH)₂. During prolonged exposure brochanite (CuSO₄ · 3Cu(OH)₂) and langite (CuSO₄· 3Cu(OH)₂) and langite (CuSO₄ · Cu(OH)₂ · 2H₂O) were also formed i. E. the Cu:S ratio of the basic copper sulphates increased with time. The formation of antlerite was preceeded by formation of an unidentified intermediate compound, probably a basic copper sulphate with a Cu:S ratio of less than three, and a simultaneous transformation of the copper (II) sulphate and copper (I, II) sulphite formed during the SO₂-exposure.     

Initial NaCl-particle induced atmospheric corrosion of zinc—Effect of CO2 and SO2

Initial corrosion and secondary spreading effects during NaCl particle induced corrosion on zinc was explored using in situ and ex situ FTIR microspectroscopy, optical microscopy, and SEM/EDAX. The secondary spreading effect which occurs upon introduction of humid air on NaCl deposited zinc surfaces was strongly dependent on the CO₂ and SO₂ content of the introduced air. Ambient level of CO₂ (350 ppm) resulted in a relatively low spreading effect, whereas the lower level of CO₂ (<5 ppm) caused a much faster spreading over a larger area. In the presence of SO₂, the secondary spreading effect was absent which could limit the cathodic process in this case. At <5 ppm CO₂, the corrosion is more localized, with the formation of simonkolleite (Zn₅(OH)₈Cl₂ · H₂O), zincite (ZnO) and sodium carbonate (Na₂CO₃), and a larger effective cathodic area. At 350 ppm CO₂, the corrosion is more general and formation of simonkolleite, hydrozincite (Zn₅(OH)₆(CO₃)₂) and sodium carbonate was observed. Sodium carbonate was mainly formed in more alkaline areas, in the inner edge of the electrolyte droplet and in the secondary spreading area. Oxidation of sulphur and concomitant sulphate formation was enhanced in the presence of NaCl particles, due to the formation of a droplet, the separation of the anodic and cathodic areas and the accompanying differences in chemical composition and pH in the surface electrolyte.