Effect of solution pH,Cl~- concentration and temperature on electrochemical behavior of PH13-8Mo steel in acidic environments

The effect of solution pH,Cl~- concentration and temperature on the electrochemical corrosion behavior of PH13-8Mo steel in acidic solution was investigated by using the electrochemical tests,scanning electron microscopy and X-ray photoelectron spectroscopy.The PH13-8Mo martensitic precipitation hardened stainless steel is in the passivity state when the pH value is above 3.0,below which the anodic polarization curves of the steel are actively dissolved.The corrosion current density gradually decreases with increasing the solution pH and decreasing Cl~- concentration and solution temperature.Pits are initiated on the sample surface in the presence of the Cl~- and gradually developed into uniform corrosion with increasing the Cl~- concentrations.Moreover,the corrosion is more serious with an increase in solution temperature.     

Cl-对690合金腐蚀电化学行为的影响

采用动电位极化、电化学阻抗、动电位电化学阻抗谱和电容测量等方法研究了690合金在一回路模拟溶液中的电化学行为.极化曲线结果表明:690合金在两种溶液中都存在较窄的钝化区间,在0.5V出现二次钝化现象.电化学阻抗表明,690合金在不含Cl^-溶液中的阻抗模值较大,而随Cl^-的加入阻抗模值变小.动电位电化学阻抗谱表明,随扫描电位正移,钝化膜在两种溶液中具有相似的变化趋势,动电位电化学阻抗谱与动电位极化曲线完全对应.690合金在0.2V下形成的钝化膜的Mott-Schottky曲线测量表明,溶液中Cl^-使得钝化膜中的施主和受主密度增大.     

Corrosion behavior of super 13Cr stainless steel in a H_2S and CO_2 environment

The corrosion behavior of 95 ksi grade super 13 Cr stainless steel in an environment consisting of H_2S and CO_2 was investigated.The results reveal that for both loading methods(constant load and four-point bending),local corrosion occurred on the surface of the samples tested at ambient temperature but was absent from the samples tested at high temperatures.The local corrosion was caused by the formation of pits at nonmetal inclusions; the pits were formed under the action of stress in an acidic environment, which was due to an acid solution.Subsequently, the corrosion extended along the direction of stress.The sensitivity of stress corrosion cracking increased because of the local corrosion.     

Effect of extrusion on corrosion behavior and corrosion mechanism of Mg-Y alloy

The influences of the hot extrusion process on the microstructure, corrosion behavior and corrosion mechanism for Mg-Y magnesium alloy were studied by means of the microstructure observation, weight loss test, electrochemical test and corrosion morphology test. The results showed that with increasing of the extrusion ratio, the shear flow line on the vertical section of the extruded alloy increased, the shear bands parallel lines became more clearly visible, and a large number of fine equiaxed grains distributed in parallel with the flow lines. The open circuit potential had a certain degree of improvement after extrusion, the open circuit potential increased with increment of extrusion ratio, and the corrosion potential of the vertical section was higher than that of the same alloy in the same compression ratio. The shift rate of the corrosion potential relatively became larger with increasing of the extrusion ratio, and the cathode corrosion current corresponding to the branch migration shifted to the positive direction. The high frequency capacitive arc increased with increment of the extrusion ratio, and the radius of capacitive arc of the vertical section was slightly larger than that of the transverse section. The corrosion morphologies of Mg-0.25 Y alloy were uniform corrosion, and the corrosion morphologies of Mg-(2.5, 5, 8 and 15) were the pitting corrosion and the small range, deep depth localized corrosion.     

Effect of inhibitory species on electrochemical corrosion of high copper amalgam

This investigation evaluates the corrosion potential of high copper amalgam containing inhibitory species, sodium phosphate and sodium citrate, in artificial saliva at different pH levels. The data revealed that the phosphate incorporated in high copper amalgam leads to increase in passivation of the alloy as compared to less or even negative effect of citrate incorporation. The linear steady potential of the amalgam was closer to the reversible potentials corresponding to hydrogen evolution and tin oxide formation. The corrosion potential does not respond reversibly to pH of the saliva solution due to the pronounced passivation of the high pH levels.     

预拉伸变形对Al-Cu-Mg合金腐蚀性能的影响

采用表面腐蚀、慢应变速率拉伸(SSRT)实验研究预拉伸变形对Al-Cu-Mg合金腐蚀性能的影响。利用扫描电镜观察分析Al-Cu-Mg合金断口形貌及结构。结果表明,预拉伸变形可显著提高合金位错密度,为H原子的扩散提供更多的通道,因此,在相同腐蚀时间下,3.5%NaCl溶液中T8态Al-Cu-Mg合金的腐蚀速率高于T6态。此外,预拉伸变形可显著增加S相弥散度,使得S相两侧的无沉淀析出带变窄,有效降低了晶界和晶内的电位差,从而降低晶界沉淀相的溶解速度,因此,在同一热处理状态下,Al-Cu-Mg合金在饱和H2S溶液中的应力腐蚀开裂敏感性高于干燥空气中的腐蚀开裂敏感性。同一应变速率下,T8态Al-Cu-Mg合金具有比T6态更好的抗应力腐蚀性能,表明预拉伸变形处理可显著提高合金的抗应力腐蚀性能。     

S31609奥氏体不锈钢中残留δ铁素体的腐蚀行为

对含残留δ铁素体的S31609奥氏体不锈钢进行650 ℃、保温2h的敏化处理,通过金相蚀刻、电子探针和扫描开尔文探针显微镜分析并比较残留δ铁素体和奥氏体晶界处的腐蚀特征.结果表明,随着敏化过程中残留δ铁素体快速分解成稳定的σ相、二次奥氏体(γ2)和Cr23C6,尽管奥氏体晶界和δ/γ相界处没有明显的Cr/Mo贫化区,但...     

温度对X80管线钢及其焊缝腐蚀行为的影响

利用动电位极化和交流阻抗技术研究了温度因素对X80管线钢及其焊缝在库尔勒土壤模拟溶液中电化学腐蚀行为的影响。结果表明:随着温度的升高,试样腐蚀电流密度呈现先增大后减小的趋势,而且增大的幅度逐渐缩小。当温度为80℃时,电荷转移电阻Rt出现极小值,此时试样腐蚀现象最严重。当温度为90℃时,电极腐蚀反应受到抑制,金属腐蚀速率明显减小;相同温度下,X80管线钢焊缝的腐蚀程度高于母材,焊缝耐腐蚀性能较差。     

扫描Kelvin探针研究缺陷涂层的膜下腐蚀电化学行为

应用扫描Kelvin探针原位研究盐雾和干湿周浸环境中缺陷涂层膜下的腐蚀行为.结果显示:在两种腐蚀环境中,缺陷涂层均分为缺陷、阴极剥离及完好涂层区域;Kelvin电位的分布相同,缺陷处最高,完整涂层处最低.Kelvin电位分布峰的直径随时间的延长而增大,表明剥离区域扩大.干湿周浸环境中,Kelvin电位的最大值V_max随时间变化不明显,V_min在逐渐下降后达到谷值,随后升高;盐雾环境中由于电解质溶液持续扩散和盐雾颗粒极强的腐蚀性,Kelvin电位随时间的变化规律为V_min在起始阶段达到最小值,随后升高.由V_max-V_min的变化规律得出,干湿周浸环境下腐蚀倾向性在试验开始5h后达到最大,而在盐雾环境下,试验开始阶段腐蚀倾向性就达到最大,且要高于干湿周浸环境.     

pH值对货油舱用耐蚀钢腐蚀特性的影响

针对油轮货油舱底部的高氯离子强酸性腐蚀环境,参照了IMO《货油舱用耐蚀钢实验程序》的要求,深入研究了腐蚀溶液的pH值对其腐蚀特性的影响,对比分析了普通E36级船板钢以及等强度级别的耐蚀船板钢腐蚀行为的差异.研究结果表明,pH值对钢的腐蚀速率有显著影响.pH＜3.0时,耐蚀钢的耐腐蚀性能,尤其是耐点蚀性能明显优于传统钢;pH≥3.0时,耐蚀钢和传统钢的腐蚀速率未表现出明显差异.强酸性氯离子环境下,实验钢的纯净度、微量耐蚀合金设计、显微组织共同决定了其耐腐蚀性能.钢中的非金属夹杂物是诱发局部腐蚀的主要原因;Cu、Ni、Sn元素的复合添加能显著提高耐蚀钢的腐蚀电位,同时耐蚀合金元素在锈层内部富集,提高了耐蚀钢表面锈层的致密性与稳定性;单一均匀的贝氏体显微组织有利于提高实验钢在酸性氯离子环境下的耐蚀性能,这主要是由于贝氏体组织中富碳相较少且分布均匀.     

超级13Cr在H2S和CO2共存环境下的腐蚀行为影响研究

对CO2和H2S共存环境中95 ksi钢级超级13Cr钢的腐蚀行为进行了研究,发现常温条件下H2S和CO2共存环境中,无论是采用恒载荷的方法还是四点弯曲的方法,都在试样的表面出现了局部腐蚀,而在高温条件下未发生点蚀和应力腐蚀现象。分析结果表明,95 ksi钢级的超级马氏体不锈钢在常温H2S和CO2共存环境中出现的局部腐蚀主要是因为夹杂物在应力集中和酸性溶液的作用下形成点蚀,并沿着相同应力水平的区域扩展,局部腐蚀增加了应力腐蚀开裂的敏感性。     

Effect of vacuum ion-plasma treatment on the electrochemical corrosion characteristics of titanium-alloy implants

The effect of mechanical polishing and various types of vacuum ion-plasma treatment of model implants made of VT1-0, VT20, and VT6 titanium alloys on their electrochemical corrosion characteristics in a 0.9% NaCl solution (Ringer’s solution) is studied. Ion nitriding and the evaporation of a titanium nitride coating are shown to form a surface structure that provides an increase in the hardness, wear resistance, and corrosion resistance of these implants.     

表面状态对核级316LN不锈钢电化学腐蚀行为的影响

表征了打磨态和机械抛光态316LN不锈钢表面的粗糙度、表面残余应变和表面电子功函数的分布,并研究了打磨态和机械抛光态样品在硼酸盐溶液中电化学腐蚀行为的差异.与机械抛光态316LN不锈钢相比,打磨处理后样品表面较为粗糙,且表面的微观残余应变较大,近表面产生约50μm的加工硬化层.表面粗糙度和微观应变的增加引起打磨态表面电化学活性的增大,从而促进316LN不锈钢在硼酸盐溶液中腐蚀.机械抛光处理降低了表面钝化膜的载流子密度(供体和受体),并增大了钝化膜的阻抗,提高了钝化膜的致密性和保护性,能够有效抑制金属的进一步腐蚀.     

时效制度对2A97铝锂合金腐蚀行为和微观组织的影响

通过拉伸性能测试、晶间腐蚀(IGC)和剥落腐蚀实验(EXCO)以及透射电镜(TEM)观察,研究时效制度对2A97铝锂合金力学性能、晶间腐蚀行为、剥落腐蚀行为和微观组织的影响.结果表明:135℃/36 h+175℃的双级时效比135℃的单级时效更有利于提高2A97铝锂合金的力学性能和耐腐蚀性能;随着175℃下的第二级时效...     

残余应力对金属材料局部腐蚀行为的影响

基于残余应力测试新方法与先进电化学测试技术的进展, 围绕残余应力类型和大小对金属材料点蚀以及应力腐蚀行为的作用机理进行了总结和归纳. 研究发现, 尽管残余压应力对腐蚀行为的抑制作用得到了大量实验的证实, 但是在不同条件下其作用方式以及机理不尽相同, 并且与材料的结构特点以及腐蚀产物等密切相关. 同时, 残余拉应力的作用尚不明确, 受到材料类型和其他因素耦合的严重影响. 另外, 在某些环境下, 影响腐蚀行为的关键是残余应力梯度或残余应力的某个临界值. 但是对有色金属的研究表明残余拉应力和压应力均会导致基体中位错和微应变等结构缺陷增加, 进而促进点蚀敏感性, 降低材料服役性能. 最后, 对目前研究存在的局限进行了讨论和展望.      

残余应力对金属材料局部腐蚀行为的影响

基于残余应力测试新方法与先进电化学测试技术的进展,围绕残余应力类型和大小对金属材料点蚀以及应力腐蚀行为的作用机理进行了总结和归纳.研究发现,尽管残余压应力对腐蚀行为的抑制作用得到了大量实验的证实,但是在不同条件下其作用方式以及机理不尽相同,并且与材料的结构特点以及腐蚀产物等密切相关.同时,残余拉应力的作用尚不明确,受到材料类型和其他因素耦合的严重影响.另外,在某些环境下,影响腐蚀行为的关键是残余应力梯度或残余应力的某个临界值.但是对有色金属的研究表明残余拉应力和压应力均会导致基体中位错和微应变等结构缺陷增加,进而促进点蚀敏感性,降低材料服役性能.最后,对目前研究存在的局限进行了讨论和展望.     

霉菌对超高强钢腐蚀行为的影响

采用扫描Kelvin探针测试技术,研究了300M钢、Aermet100钢与超高强不锈钢在黄曲霉、黑曲霉、球毛壳霉、绳状青霉和杂色曲霉组成的混合霉菌菌种作用下的腐蚀行为.通过扫描电镜结合能谱分析对霉菌在三种超高强钢上的生长进行了观察和分析.300M钢试样上霉菌呈现分散式堆积生长,数量逐渐增加;Aermet100钢试样上霉菌呈现分散式单个生长方式,数量逐渐增加;超高强不锈钢上霉菌呈现放射式网状生长方式,数量急剧增加,在钢表面形成一层生物膜.霉菌实验后,三种超高强钢表面都发生一定的腐蚀.300M钢腐蚀最严重,蚀坑宽而浅;Aermet100钢次之,蚀坑窄而深;超高强不锈钢的耐蚀性最好.扫描Kelvin探针测试结果表明,霉菌一定程度上能促进300M钢和Aermet100钢的腐蚀,而对超高强度不锈钢的腐蚀行为有一定抑制作用.     

阳极电流密度对NiFe2O4基惰性阳极 电解腐蚀行为的影响

本文采用两步烧结法制备铝电解用NiFe_2O_4基金属陶瓷惰性阳极,重点研究了不同阳极电流密度下惰性阳极材料的电解腐蚀行为.实验结果表明:阳极电流密度在0. 2～1. 2 A/cm^2之间时,槽电压相对稳定,波动幅度较小,表现出良好的稳定性;阳极电流密度在1. 4 A/cm^2时,槽电压波动较大.电解后阳极尺寸无明显变化,棱角分明,与电解液接触面平整,无开裂、肿胀以及表层剥离的现象.从微观形貌和微区面扫描成分分析可知,阳极腐蚀速率随电流密度的增加先降低后增加.阳极电流密度为0. 8 A/cm^2时阳极腐蚀速率最低,产品铝中主要Cu、Ni和Fe杂质元素总含量最低.