The influence of NaCl and CO2 on the atmospheric corrosion of magnesium alloy AZ91

The influence of NaCl and CO₂ on the atmospheric corrosion of magnesium alloy AZ91 is studied in the laboratory. Samples were exposed under carefully controlled air and flow conditions; the relative humidity was 95%, the temperature was 22.0°C and the concentration of CO₂ was < 1 ppm or 350 ppm. Different amounts of sodium chloride (0–70 μg/cm²) were added before exposure. The corrosion products were analyzed by gravimetry, ion chromatography, X‐ray diffraction and scanning electron microscopy. Mass gain and metal loss results are reported. The combination of high humidity and NaCl is very corrosive towards AZ91. However, the NaCl‐induced corrosion is inhibited by ambient concentrations of CO₂. Exposure in the absence of CO₂ gives rise to heavy pitting, with brucite, Mg(OH)₂, being the dominant corrosion product. In the presence of CO₂ a layer of hydrated magnesium hydroxy carbonate, Mg₅(CO₃)₄(OH)₂ · 5 H₂O forms. A tentative corrosion mechanism is presented that explains the behavior in the two environments.     

氢氧化镁水热反应溶液对钛的腐蚀原因分析

文章简单介绍了卤水溶液合成氢氧化镁时金属的腐蚀机理,并采用电化学测试法研究了工业纯钛在氯化物水溶液中的腐蚀行为。结果表明工业纯钛在氯化物溶液中易发生严重的缝隙腐蚀,但发生点蚀的可能性不大。     

一种红枣去核机上料机构的设计与分析

设计了一种红枣去核机的上料机构,主要包括:振动料斗、送枣管道、拨枣转盘、拨枣齿、推枣杆、曲柄滑块机构.通过料斗的振动实现红枣定向输送,通过拨枣转盘的圆周运动和曲柄滑块机构的往复直线运动带动推枣杆完成红枣的上料.     

表面合金镀层提高钢齿轮抗点蚀性能的研究

以齿轮为研究对象,以常用的辊子模拟方法,在４５钢制辊子表面分别刷镀镍磷和镍钴合金层,与未刷镀的４５钢试件和４０Ｃｒ钢调质试件一起,进行接触疲劳强度对比试验,共试验试件４０对。结果表明,表面合金镀层能较显著地提高４５钢齿接触表面的疲劳寿命,与４０Ｃｒ钢调质试件相当,可作为４０Ｃｒ钢的代用材料,还分析了合金镀层的组织结构和性能。     

不锈钢在含有溴离子的醋酸溶液中的腐蚀

采用浸泡试验及电化学试验,对304、254 SMO和HastelloyC－276三种材料在醋酸和含有Br^-离子的醋酸溶液中的腐蚀行为进行了测试。用SEM和XPS分析点蚀形貌。结果发现材料表面所形成的钝化膜中含有Cr2O3和MoO2,对材料起保护作用。     

油田管材的SRB腐蚀

通过浸泡挂片试验,用扫描电镜和X衍射仪,对试样的腐蚀特征和腐蚀产物进行研究,发现脱硫脱硫弧菌duselfovibrio desulfuricans(D.desulf)对油田管材的腐蚀特征为点蚀,腐蚀产物为Fe9S8,同时通过电化学实验,研究了D.desulf的去极化作用,发现D.desulf的存在既有阳极去极化作用,又有阴极去极化作用。在对D．desulf的生长特性研究中,发现D.desulf的生长存在着对数生长期、生长旺盛期和衰亡期。     

不同低碳钢的点蚀诱发敏感性及诱发机理研究

选择4种冶金因素有代表性的低碳钢,通过极化试验比较了它们之间的点蚀诱发敏感性。电子探针分析了不同夹杂物在诱发点蚀过程中的腐蚀特征,显微腐蚀试验确定了点蚀诱发初期溶解产物的性质。结果表明,沸腾钢的点蚀敏感性显著低于镇静钢,稀土处理镇静钢则介于前两者之间。夹杂物是钢中主要点蚀诱发源,紧靠夹杂物的钢基体处的钝化膜保护作用最弱,点蚀均从该处基体诱发。同类杂物在不同类型钢中的点蚀诱发敏感性差异较大。同一钢中不同类型夹杂物的点蚀诱发敏感性差异很小,硫化物夹杂较其它夹杂物的点蚀诱发敏感性强。     

1Cr18Ni9Ti不锈钢的马氏体相变量与孔蚀敏感性的相关性研究

研究了AISI321亚稳态奥氏体不锈钢(1Cr18Ni9Ti)在-70℃(液氮气氛)经不同程度拉伸形变得到的含有不同α′-马氏体的试样在中性含氯离子介质中,材料的马氏体相变量与孔蚀敏感性的关系.孔蚀击穿电位、孔蚀诱导期和孔数的测试结果均表明:当α′-马氏体含量约小于5%和大于15%时,经形变诱发马氏体相变的1Cr18Ni9Ti奥氏体不锈钢在中性NaCl溶液中,孔蚀敏感性随α′-马氏体含量的增加而增大;当α′-马氏体含量在5%～15%范围内时,材料的孔蚀敏感性随α′-马氏体含量的增大而降低.     

冷却水中杀菌剂次氯酸钠、异噻唑啉酮对不锈钢的侵蚀性比较

冷却水对不锈钢有腐蚀作用,在冷却水中分别添加杀菌剂次氯酸钠和异噻唑啉酮,采用极化曲线研究了次氯酸钠和异噻唑啉酮对TP304L不锈钢电极耐蚀性能的影响.结果表明:冷却水中次氯酸钠可以促进不锈钢的点蚀,随放置时间的延长冷却水对不锈钢的侵蚀性增加;冷却水中加入异噻唑啉酮对不锈钢的极化曲线不产生影响,在放置过程中冷却水对不锈钢...     

Effect of heat treatment on the anodic oxidation of Ti–0.2 Pd alloys in chloride solutions

The effect of heat treatment of Ti and Ti–0.2 Pd alloys on their anodic oxidation was studied in deaerated 1% NaCl by means of anodic linear sweep voltammetry, SEM, TEM, EDS, optical microscopy and microhardness measurements. The specimens, as fabricated, consisted of -phase only. The -phase, intergranular or with a Widmansttäten type growth, was produced by heat treatment of the Ti–0.2 Pd alloys at the temperature range from 750 to 850 C. The -phase was transformed into the -phase during quenching. The current density against voltage curves for pure Ti and Ti–0.2 Pd, as fabricated or heat-treated, presented an initial plateau at about 1.5 V vs Ag/AgCl/KCl (3 M), an anodic peak at about 4.5 V and a current increase due to the pitting attack at about 10 V. The anodic peak was related to an oxide growth together with a solution electrolysis. Current spikes appeared at random from potentials about 8.3 V, which were related to film breakdown and repair events. The passive films of the alloys oxidized up to about 10 V presented oxidation bands parallel to the surface, with different oxygen content and microhardness, together with a structural transformation of the -phase under the titanium oxide layer. The similar behaviour of pure Ti and Ti–0.2 Pd alloys in front of pitting corrosion in chloride was due to such a structural transformation.