Internal-corrosion inhibitors for pipelines in heat-supply systems carrying water with a high oxygen content

The reliability of heat-supply systems is determined primarily by internal corrosion of the pipelines. The concentration of oxygen in the water exerts a major influence on the corrosion. In systems with a standard oxygen content, OéDF-Zn is a highly effective corrosion inhibitor. However, there are systems in which the quality of deaeration of the make-up water of the heat-supply system is low (or deaeration is nonexistent), and the concentration of oxygen is considerably above the standard value. Classed among these systems, for example, are the HWS systems, which are incorporated into closed heat-supply systems. The oxygen concentration in these systems is analyzed to assess the situation. __________ Translated from élektricheskie Stantsii, No. 6, June 2007, pp. 35–39.     

Influence of pH on the passivation behavior of 254SMO stainless steel in 3.5% NaCl solution

The potentiodynamic polarization measurement of 254SMO stainless steel (UNS 31254) was conducted in 3.5% NaCl solutions with pH ranging from 0.1 to 5. The results indicated that this stainless steel offered excellent pitting corrosion resistance in corrosive environments. Further, it also exhibited various features on the polarization curves in different pH solutions. The electrochemical constant-potential passivation treatment performed at different pH followed by XPS analysis revealed that the primary constituents of the outermost layer of the passive films formed in the weak (pH 5) and strong (pH 0.8) acid solutions are iron oxides and Cr₂O₃ and Cr(OH)₃, respectively. Molybdenum oxides, primarily in the six-valence state, existed in the outermost layer of the passive film. Only very weak signals corresponding to that of nickel oxides were detected in the film formed in the weak acid (pH 5) solution. The ICP-MS analyses indicated selective dissolution of a significant amount of Fe and a few Mo and Ni ions during the passivation treatment in the strong acid (pH 0.8) solution. No Cr dissolution was observed; this indicated that the Cr in the film is relatively stable. XPS depth profiling results showed that a similar bilayer-structured film was formed in both the solutions (pH 0.8 and 5); the outer layer of this film is primarily composed of Cr(OH)₃ and Mo(VI), and the inner layer, Cr₂O₃ and Mo(IV). The results of the examinations of passive film formations and dissolution by XPS and ICP-MS were consistent with the polarization curves.     

Failure Analysis of Fuel System Assemblies

Fuel system assemblies used on recreational watercraft failed after a short time in service in a seawater environment. Examination of the assemblies revealed significant degradation of the polyacetal connectors of the wire subassemblies. Optical and microscopic evaluations indicated the complete loss of connector material implying decomposition of the resin, along with mud-cracking and a rough surface morphology signifying chemical attack. An elemental analysis performed on both an intact connector and degraded connector suggested a potential chemical agent in the form of zinc chloride. At elevated temperatures, concentrated zinc chloride solutions are known to decompose polyacetal resins. The source of the zinc chloride was established as corrosion products that resulted during the dezincification of the internal brass connector through exposure to saltwater in the application.     

Austenitizing treatment influence on the electrochemical corrosion behavior of 0.3C-14Cr-3Mo martensitic stainless steel

Effects of austenitizing treatment temperatures on aqueous corrosion properties of martensitic stainless steels were investigated by electrochemical tests (potentiodynamic test, potentiostatic test and electrochemical impedance spectroscopy), and surface analyses (optical microscopy and XRD). The results of potentiodynamic test revealed that the breakdown potential increased with the increased austenitizing temperature, indicating increased relative resistance to initiation of localized corrosion. EIS measurements showed that MSS3 (1030 °C) exhibits larger polarization resistance value than MSS1 (970 °C) and MSS2 (1000 °C) at passive and breakdown states. This was caused by decreasing the amount of Cr-rich M₂₃C₆ carbide which acts as preferential sites for pitting corrosion.     

复合绝缘子耐电腐蚀特点及其电蚀老化区域性的差异

为了了解复合绝缘子外绝缘材质电蚀老化状态和区域性的差异,对Al(OH)3耐电腐蚀机理、外绝缘材质中Al(OH)3颗粒分布状态和环境污湿因素的实际情况进行了研究。Al(OH)3颗粒分解成水蒸气、析出白色粉末状氧化铝,并催化生成二氧化碳,将使外绝缘材质逐渐微观减薄和加大表面的粗糙度,而引起电蚀老化的污湿环境因素,近期不可能得到改善,因此必然引起其电蚀老化出现区域性差异。此外,外绝缘憎水表面污珠场强变化引起的电晕也是促使电蚀老化的重要因素。     

Improvement in Stress Corrosion Crack Growth Resistance of an Austempered Cast Steel by a Novel Two-Step Austempering Process

An investigation was carried out to examine the influence of microstructure on the stress corrosion cracking (SCC) growth behavior of an austempered high-carbon (1.00%), high-silicon (3.00%), and high-manganese (2.00%) cast steel. Compact tension specimens were prepared from this cast steel as per American Society for Testing Materials standard E-399 and were given four different heat treatments to produce different microstructures. The SCC behavior of these specimens was studied in 3.5% NaCl solution. The test results indicate the K_ISCCvalue of the material increases as the austenite content increases. Significant improvement in SCC resistance was achieved by using a novel two-step austempering process. Intergranular crack growth was observed in all these specimens.     

复合内衬在燃油加热炉中的应用

对导热油加热炉炉壁温度升高的原因进行了分析,介绍了新型复合内衬的特点,并对其技术特点、施工工艺及应用效果进行了简单阐述。     

两栖装甲装备新型防腐材料的研究

沿海地区特殊海洋环境造成装甲装备的严重腐蚀,为了研制一种新型的耐蚀有机涂层,该文作者研究了有机硅改性环氧树脂的化学反应,并对改性树脂的性能进行了测试分析.结果表明,改性树脂克服了环氧树脂的耐温性差、亲水性强以及盐水渗透率高的性能缺陷,为进一步制备该地区装甲装备防腐涂料奠定基础.     

腐蚀环境中海工混凝土抗氯离子侵蚀性

模拟我国南方沿海浪溅区和水位变动区的海工钢筋混凝土结构物的腐蚀环境，对掺入粉煤灰和矿渣的混凝土抗氯离子侵蚀性进行了试验。结果表明，在水灰比相同的条件下，加掺和料的混凝土抗氯离子侵蚀性高于普通混凝土。     

Corrosion Control by water‐soluble extracts from leaves of economic plants

Water extracts from leaves of date palm, phoenix dactylifera, henna, Lawsonia inermis, and corn, Zea mays, were tested as corrosion inhibitors for steel, aluminum, copper and brass in acid chloride and sodium hydroxide solutions using weight loss, solution analysis and potential measurements. The inhibition action was found to critically depend on metal type and solution composition. Only, date palm and henna extracts were found highly effective in reducing corrosion rate of steel in acid chloride solutions and aluminum in sodium hydroxide solutions. The inhibition efficiency increased with increasing the concentration of the extract. The inhibition was interpreted in terms of chemisorption of some active ingredients in the leaves according to Temkin isotherm.