重碳酸盐溶液中SO_4^(2-)和Cl^-对低碳钢活化/钝化腐蚀行为的影响

在除O_2的0.1 mol/L NaHCO_3,0.1 mol/L NaHCO_3+0.1 mol/L Na_2SO_4以及0.1 mol/L NaHCO_3+0.1 mol/L NaCl溶液中,用恒电位法在低碳钢电极表面制备腐蚀产物,并原位监测低碳钢的开路电位,用SEM观察腐蚀形貌,用XRD确定腐蚀产物的相组成.结果表明.在0.1 mol/L NaHCO_3溶液中,低碳钢的开路电位最终处于再钝化区间,其表面未观察到明显的腐蚀现象;在0.1 mol/L NaHCO_3+0.1 mol/L Na_2SO4溶液中,低碳钢的开路电位最终处于再活化区间,其表面发生均匀腐蚀;在0.1 mol/L NaHCO_3+0.1 mol/L NaCl溶液中,低碳钢的开路电位最终亦处于再活化区间,而其表面却发生局部腐蚀,XRD结果表明,低碳钢表面的腐蚀产物主要为Fe_3O_4和α-FeOOH.

硼酸缓冲溶液中pH值和腐蚀产物对低碳钢活化/钝化敏感性的影响

研究了在pH值分别为8,9和10的除氧硼酸缓冲溶液中,低碳钢腐蚀产物对其活化/钝化敏感性的影响.实验结果表明,在pH值为8时,低碳钢一直处于活性溶解状态,不受腐蚀产物影响;在pH值为9和10时,表面腐蚀产物使低碳钢钝化,其腐蚀电位最后稳定于钝化区间.XPS和XRD等分析结果表明,腐蚀产物由Fe_6(OH)_(12)B_4O_7和γ-FeOOH组成.腐蚀产物覆盖的低碳钢比裸低碳钢更容易发牛钝化.

Activity of Catalyst for Liquid Phase Methanol Synthesis

the effects of reduction procedure, reaction temperature andcomposition of feed gas on the activity of a CuO-ZnO-Al_2O_3 catalystfor liquid phase methanol synthesis were studied. An optimizedprocedure different from conventional ones was developed to obtainhigher activity and better stability of the catalyst. Both CO andCO_2 in the feed gas were found to be necessary to maintain theactivity of catalyst in the synthesis process. Reaction temperaturewas limited up to 523 K, otherwise the catalyst will be deactivatedrapidly.

Q235钢在不同浓度碳酸氢钠溶液中的有氧腐蚀行为

利用电化学测量技术、表面表征技术和失重实验研究了Q235低碳钢在同一溶解氧不同浓度NaHCO_(3)溶液中的活化/钝化行为。研究表明,Q235钢在浸泡初期和后期,腐蚀行为显著不同,尤其是在低浓度NaHCO_(3)溶液中,这与样品表面覆盖的腐蚀产物有关。在高溶解氧条件下,HCO_(3)^(-)浓度影响低碳钢的腐蚀动力学。当HCO_(3)^(-)浓度较低时,低碳钢腐蚀反应主要受电荷转移过程控制;而在高浓度NaHCO_(3)溶液中,腐蚀反应则主要受扩散过程控制。HCO_(3)^(-)通过影响Q235钢表面腐蚀产物形态及致密度进而影响Q235钢的腐蚀速率。随HCO_(3)^(-)浓度的增加,腐蚀产物致密度增加,保护性增强,Q235钢腐蚀速率降低。