Synergistic Effect of Mo,W, Mn and Cr on the Passivation Behavior of a Fe-Based Amorphous Alloy Coating

In this work, the electrochemical behaviors of SAM2 X5 Fe-based amorphous alloy coating and hard chromium coating were comparatively studied in 3.5 wt% Na Cl solution. In comparison with the hard chromium coating, the SAM2 X5 coating exhibited a wider and stable passive region with lower passive current density in the potentiodynamic polarization and showed a considerably lower current density at different anodic potentials in the potentiostatic polarization. In order to understand the passivation mechanism of the Fe-based amorphous coating, the components of the passive films formed at various polarization potentials were examined by X-ray photoelectron spectroscopy. The synergistic effect of Mo, W, Mn and Cr in the passive films was systemically analyzed. It has been revealed that Mo and W facilitate the formation of compact and stable Cr_2O_3 passive film at lower potentials, and the substantial enrichment of Mn in the passive film enhances the passivation ability at relatively higher potentials. The deep understanding of the passivation characteristics in multicomponent alloy systems could provide a guide for the design of corrosion-resistant amorphous alloy coatings for engineering applications.     

Passive Behavior of Ultra-Fine-Grained 1050 Aluminum Alloy Produced by Accumulative Roll Bonding in a Borate Buffer Solution

In this study, the effect of the ARB process on the passive behavior of ultra-fine-grained 1050 aluminum alloy in a borate buffer solution(p H 6.0) has been investigated. The result of the microhardness tests revealed that the microhardness values increase with an increasing number of ARB cycles. The potentiodynamic polarization plots revealed that the higher number of cycles for the specimens proceeds with the ARB process rather than annealing yield to lower corrosion and passive current densities and more noble corrosion potential values. Moreover, electrochemical impedance spectroscopy measurements showed that increasing the number of ARB cycles offers better conditions for forming the passive films.     

The effect of counter anions on corrosion resistance of steel covered by bi-layered polypyrrole film

The bi-layered polypyrrole (PPy) coatings were investigated for corrosion prevention of a carbon steel. The inner layer was doped with the Keggin structure anions of (PMo₁₂) and anions for stabilization of the passive oxide film at the metal-polymer interface, and the outer layer was doped with four organic anions of dihydroxynaphthalenedisulfonate (DHNDS), naphthalenedisulfonate (NDS), anthraquinonedisulfonate (AnqDS) or dodecylsulfate (DoS) for inhibition of the decomposition and release of PMo₁₂. The corrosion tests were performed in 3.5 wt.% NaCl aqueous solution. The corrosion resistance of the steels covered by the bi-layered PPy films was found in the following order: PPy-PMo₁₂/PPy-DHNDS < PPy-PMo₁₂/PPy-NDS < PPy-PMo₁₂/AnqDS < PPy-PMo₁₂/PPy-DoS. The performance of corrosion protection related to the oxidized state of the polymer was discussed.     

不同温度条件下铬酸盐钝化镀锡板的耐蚀性研究

以镀锡钢板钝化工艺中的钝化温度为研究对象,使用金相观察、X射线光电子能谱(XPS)、电化学等试验方法,讨论了不同温度条件对铬酸盐钝化镀锡板的耐中性溶液腐蚀、耐硫蚀、耐酸蚀等性能的影响以及钝化膜表面元素铬的元素价态.结果表明:铬元素在钝化膜中的状态为2种铬的化合物组成,分别为Cr2O3和Cr(OH)3.随着钝化温度的增加,钝化镀锡板耐中性溶液腐蚀有不同程度的增强,镀锡板耐硫蚀以及耐酸蚀性能均提高.     

Improved Corrosion Resistance of Selective Laser Melted Ti–5Cu Alloy Using Atomized Ti–5Cu Powder

The different types of metal powder used for selective laser melting(SLM) process would cause distinct corrosion behavior due to the uniformity of the obtained microstructure.The SLM-produced Ti–5Cu alloy using atomized Ti–5Cu metal powder(SLMed Ti–5Cu) in this work reveals a relatively uniform microstructure with overwhelming acicular α/α′ phase and shows great advantages on corrosion resistance compared with the SLM-produced Ti–5Cu alloy using the mixture powder(SLMedM Ti–5Cu).The effect of the micro-galvanic cells decreases due to the undetectable Ti_2Cu phase in the microstructure of the SLMed Ti–5Cu.An apparent passivation behavior was observed for SLMed Ti–5Cu instead of severe pitting phenomenon for the SLMed-M Ti–5Cu.The charge transfer resistance of SLMed Ti–5Cu in this work is 10.09 ± 2.63 MΩ cm~2, which is significantly higher than that of SLMed-M Ti–5Cu(4.76 MΩ cm~2).The above result indicates the atomized Ti–5Cu powder plays an important role in the formation of the uniform microstructure of SLMed product, thereby enhancing its corrosion resistance in Hank's solution at 37 ℃.     

铜包铁粉末表面的钝化处理

通过对2种苯并三氮唑(BTA)有机添加剂复合配方和1种常用的钝化剂对比试验,探索了BTA系复配钝化剂在铜包铁粉末防变色钝化处理中的钝化效果及机理,通过硝酸滴定试验、氨水滴定试验、SO2加速腐蚀试验、大气腐蚀试验及温湿耐蚀试验,得出铜包铁粉末表面钝化的最佳工艺为:0.5%BTA,1～3g/L OP-10,温度为50～60℃,处理时间为3～5 min.BTA复配体系处理后的防护效果好于BTA单一体系,单一BTA处理后的钝化效果好于目前常用的钾肥皂钝化效果.     

电磁振动雾化-速凝镁粉钝化表征研究

用电磁振动雾化-速凝法制备了粒度为0.2～1.0 mm的镁粉,研究了这种速凝镁粉在1 000 ℃的阻燃时间.结果表明,速凝镁粉阻燃时间为17～21 s,而铣削-钝化镁粉阻燃时间为11～14 s.扫描电镜和能谱仪观察和分析发现,速凝镁粉存在表面碳富集,迅速凝固产生的致密表面,增强了粉粒表面的化学稳定性,产生了钝化效果.     

预硫化加氢催化剂钝化技术研究进展

钝化是预硫化加氢催化剂的关键处理过程。预硫化催化剂经过钝化处理后,有效抑制了自热性质和硫的脱离,便于催化剂的存储和运输,并保持催化剂的活性,有利于器外预硫化催化剂的大规模生产。介绍了气相、液相和固相3种钝化方式、钝化机理及其应用和研究进展。     

Electrochemical behaviour of titanium in H2SO4-MnSO4 electrolytes

The corrosion of titanium in H₂SO₄ electrolytes (0.001-1.0 M) at temperatures from ambient to 98 °C has been investigated using steady-state polarization measurements. Four distinct regions of behaviour were identified, namely active corrosion, the active-passive transition, passive region and the dielectric breakdown region. The active corrosion and active-passive transition were characterized by anodic peak current (i_m) and voltage (E_m), which in turn were found to vary with the experimental conditions, i.e., d(log?(im))/dpH=−0.8±0.1 and dE_m/dpH which was −71 mV at 98 °C, −58 mV at 80 °C and −28 mV at 60 °C. The activation energy for titanium corrosion, determined from temperature studies, was found to be 67.7 kJ mol⁻¹ in 0.1 M H₂SO₄ and 56.7 kJ mol⁻¹ in 1.0 M H₂SO₄. The dielectric breakdown voltage (E_d) of the passive TiO₂ film was found to vary depending on how much TiO₂ was present. The inclusion of Mn²⁺ into the H₂SO₄ electrolyte, as is done during the commercial electrodeposition of manganese dioxide, resulted in a decrease in titanium corrosion current, possibly due to Mn²⁺ adsorption limiting electrolyte access to the substrate.