Al/H62黄铜和Al/304不锈钢在乙二醇溶液中的电偶腐蚀

采用电化学方法研究了浓度、温度、阴阳极面积比的变化对乙二醇水溶液中3A21铝合金/H62黄铜(Al/Cu)、3A21铝合金/304不锈钢(Al/SS)两种电偶对的腐蚀行为的影响。通过扫描电子显微镜观察了电偶对中铝合金局部腐蚀形貌。结果表明:随着乙二醇浓度的升高,Al/Cu和Al/SS电偶对的平均电偶电流密度Ig下降。随着温度的升高或Sc/Sa比例的增大,Al/Cu和Al/SS电偶对的Ig增大;相同条件下,Al/Cu电偶对Ig均大于Al/SS电偶对,Al/Cu和Al/SS两种电偶对具有相似的电偶腐蚀规律。     

镍基合金Inconel 718与抗硫油套管钢在模拟气田地层水中的电偶腐蚀

采用电化学方法研究了在模拟罗家寨气田地层水中镍基合金Inconel718和抗硫管材VM80 SS之间的电偶腐蚀特征和电偶效应.结果表明,Inconel 718和VM80 SS的自腐蚀电位分别为-260 mV和-770 mV,当阴阳极面积比S=0.25,1,4,8时,电偶电位Eg处于-760 mV～-700 mV之间,随S增大,Eg正移,Ig/Aa的初始值、稳态值和平均值均增大;而Ig/Ac的初始值降低,稳态值变化不大.根据混合电位理论计算的VM80SS的电偶腐蚀效应γ随S增大而增大,γ=1.14～4.82.     

X65/316L电偶对在模拟油田产出水中的电偶腐蚀行为

采用电化学方法研究了X65/316L电偶对在模拟油田产出水环境中的电偶腐蚀行为。结果表明,在pH值为7.15的模拟油田产出水中,当阴阳极面积比为2、1和0.5时,电偶电位在-708～-735mV之间,随着阴阳极面积比的增大,电偶电位正移,阳极电偶电流密度增大,但阴极电偶电流密度的变化范围不大。(SCE)电偶腐蚀效应随阴阳极面积比的增大而增大。阴阳极面积比为1时,电偶电流密度随pH值的减小而增大。     

Q235-304L电偶对在Na2S溶液中的电偶腐蚀行为研究

用电化学法和浸泡法研究了Q235-304L电偶对在3种不同浓度的Na2S溶液中的电偶腐蚀行为,用SEM观察试样的表面形貌.结果表明:在3种溶液中Q235钢的阳极过程均为混合控制,而304L的阴阳极过程均为电化学控制;偶接后Q235钢表面阳极金属的溶解过程与阴极过程同时进行,其阳极溶解电流大于电偶电流值;电偶腐蚀效应随阴阳极面积比的增大而增大;随着S2-浓度的升高,电偶对中Q235钢的腐蚀速率减小,电偶腐蚀效应也随之降低.     

氯离子和电偶腐蚀对碳钢在热钾碱溶液中腐蚀的影响

研究了Cl-对碳钢和不锈钢在(K2CO3+KHCO3+ V2O5)溶液中腐蚀的影响,结果表明Cl-对阳极钝化曲线所示的腐蚀电位、钝化区间、过钝化电位和析氧过程无明显影响,未见试样有孔蚀的迹象.但随着Cl-离子浓度增大,其维钝电流密度也增大.90℃时,不锈钢-碳钢在此溶液中构成电偶腐蚀时,测得碳钢腐蚀速率为0.064 mm/a,比未成偶对时碳钢的腐蚀速率大一倍.90℃时,将已钝化的不锈钢-碳钢在(K2CO3+KHCO3)溶液中构成电偶腐蚀时,测得碳钢腐蚀速率为4.0 mm/a,比含有V2O5溶液中碳钢的腐蚀速率大64倍.     

H_2S/CO_2介质中P110钢表面的局部电偶腐蚀行为

通过模拟环境中的电偶电流的跟踪测试,研究了P110钢表面腐蚀产物膜层/金属基体所构成的电偶电流随温度、时间和面积比等因素的变化规律。结果表明,40℃时,有膜层覆盖的P110钢电极作为阳极发生垢下阳极溶解,而裸露电极作为阴极反应;在60℃时,偶接初始阶段,有膜层覆盖的P110钢电极先发生垢下阳极溶解,但很快偶接电极之间会出现电流反转,裸露电极由阴极变成阳极而被腐蚀;不同面积比的裸露电极/膜层覆盖电极偶接时,电偶电位相差不大,随着阳/阴极面积比的增大而负移,电偶电流密度绝对值则随阳/阴极面积比的增大而减小。随着时间延长,稳态条件下,裸露电极/膜层覆盖电极的电偶电流密度趋近为零;而在动态变化条件下,则很可能会形成小阳极大阴极的情况,从而会导致难以极化,最终出现腐蚀穿孔的危险。     

两种不锈钢在模拟消声器环境中的电偶腐蚀行为

采用氧化/冷凝液浸泡循环实验方法模拟汽车消声器内部环境,研究了409和304两种不锈钢在冷凝液中的电偶腐蚀行为。结果表明,无氧化作用时两种不锈钢间电偶腐蚀效应较弱,304钢对409钢的加速腐蚀作用很小。循环实验过程中,偶合电位较低时偶合电流密度往往较大。热氧化将明显增大两种不锈钢发生电偶腐蚀的倾向性,但氧化温度为250℃时稳定偶合电流密度较小、电偶腐蚀效应不显著,而氧化温度为400℃时409钢在循环过程中将发生局部腐蚀,呈现出较大的偶合电流密度,电偶腐蚀效应较强。     

碳钢/Ti和碳钢/Ti/海军黄铜在海水中电偶腐蚀的研究

采用动电位极化技术及失重法研究Q235B碳钢/TA2钛和Q235B碳钢/TA2钛/海军黄铜在海水中的电偶腐蚀规律.测定了Q235B碳钢、TA2钛和海军黄铜在海水中的自然腐蚀电位、腐蚀速率和稳态极化曲线,测定了不同面积比时电偶对电偶电流的大小、方向,电偶电位以及电偶对阳极和阴极的失重速率,由电偶对不同面积比的数据得到Q235B碳钢被Ti电偶极化的动态极化曲线.结果表明,阳极的腐蚀速率随阴/阳极面积比的增大而增加;阳极腐蚀速率随阴/阳极面积比的增大有一个极限值,即当阴/阳极面积比大于这个极限值时,阳极腐蚀速率不再增加.这三种金属构成的电偶对,海军黄铜是这个系统的阴极,受到碳钢的保护.     

大气环境条件下电力金属材料的电偶腐蚀研究

对由紫铜和Q235碳钢、Zn、以及304不锈钢垫圈组成的3种电偶组件在福建省16个地点进行了为期1 a的大气暴露试验,获得了3种电偶组件在不同大气环境下的腐蚀失重数据,并结合各地区的气象和环境数据、试样表面形貌以及腐蚀产物成分,对典型地区的电偶腐蚀行为进行了分析。结果表明,在大气环境下,Cu与Q235碳钢、Zn耦合后Cu为阴极,与304不锈钢耦合后Cu为阳极,电偶作用明显加速了阳极金属的腐蚀,且与大气环境有直接的关联。电偶效应规律为:γ_(Cu-Zn)γ_(Cu-Q235)γ_(Cu-304SS)。     

交流阻抗法研究工业纯钛的性能

采用交流阻抗技术结合恒电流阴极充氢和动态阴、阳 极极化法，研究了工业纯钛在海水中的阴极极化性能.结果表明：极化曲线所表现的lgI～E关系与交流阻抗法得出的lg(Rp)～-E关系和lg(Cd)～-E关系有对应性；交流阻抗的结果更直接地反映工业纯钛在海水中阴极极化后的表面状态变化，极化电阻Rp随着阴极电位的增大，呈下降趋势，微分电容Cd随着阴极电位的增大，呈上升趋势.充氢后的钛阳极溶解电流增大.     

面积比对Al 6061-SS 304电偶腐蚀行为的影响

对30%硝酸环境中的Al 6061-SS 304电偶对开展浸泡实验和电化学实验,研究了Al 6061材料在30%硝酸环境中的电偶腐蚀现象和不同阴阳面积比对腐蚀行为的影响,借助SEM、EDS、电化学测量等方法对腐蚀前后Al 6061的表面形貌、腐蚀坑数量、电化学参数进行了测量与分析。结果表明:Al 6061耦合SS 304后,两者间的腐蚀驱动电位差达到583 mV,Al 6061作为反应阳极发生溶解腐蚀;在SEM照片中可以明显看出耦合后出现了三类电偶腐蚀现象,其中第二相粒子与铝基体耦合引起的微电偶腐蚀是腐蚀坑的主要类型。同时,阴阳面积比增加导致电偶电位减小和腐蚀电流增大,电偶电流与阴阳面积比满足定量关系式,且经K-S检验理论与实际吻合度高。     

船舶用Ti70合金在人工海水中的腐蚀行为研究

采用全浸腐蚀和电偶腐蚀实验,研究了Ti70合金的均匀腐蚀行为,以及与945钢的电偶腐蚀行为。结果表明：Ti70合金耐蚀性能极好,在60 ℃人工海水浸泡30 d后试样出现了轻微增重,腐蚀速率为-5.857×10^-4 mm/a,达到了I级完全耐蚀级别;Ti70合金自腐蚀电位远高于945钢,两者偶联时945钢将作为阳极被加速腐蚀;随着Ti70/945钢偶对面积比增加,945钢质量损失、以及电偶腐蚀电流和电偶腐蚀系数均逐渐增加,当两者偶对面积比为1∶1时,电偶腐蚀敏感等级达到了D级,因此当Ti70合金与945钢接触使用时需对945钢进行阴极保护。     

Galvanic Corrosion of a Carbon Steel-Stainless Steel Couple in Sulfide Solutions

The galvanic corrosion behavior of carbon steel-stainless steel couples with various cathode/anode area ratios was investigated in S ²⁻-containing solutions, which were in equilibrium with air, by electrochemical measurements, immersion test, and surface characterization. It is found that the galvanic corrosion effect on carbon steel anode increases with the cathode/anode area ratios, and decreases with the increasing concentration of S²⁻ in the solution. A layer of sulfide film is formed on carbon steel surface, which protects it from corrosion. When the cathode/anode area ratio is 1:1, the potentiodynamic polarization curve measurement and the weight-loss determination give the identical measurement of the galvanic corrosion effect. With the increase of the cathode/anode area ratio, the electrochemical method may not be accurate to determine the galvanic effect. The anodic dissolution current density of carbon steel cannot be approximated simply with the galvanic current density.     

Galvanic corrosion of A1 alloys — II. Effect of solution composition

Galvanic corrosion of the A1 alloys 1100, 2024, 2219, 6061 and 7075 coupled to Cu, stainless steel 304L, Ti-6A1-4V, 4130 steel or zinc has been studied in 3·5% MaCl, tapwater and distilled water using electrochemical and weight loss data. In 3·5% NaCl the galvanic effect decreases in the order Cu > 4130 steel > SS304L > Ti-6A1-4V for A1 alloys coupled to one of these metals, while in tapwater and distilled water the ranking is Cu > SS304L ～ Ti-6A1-4V > 4130 steel. Zinc, although being the anode in all galvanic couples, can sometimes accelerate corrosion rates of A1 alloys. Dissolution rates of A1 alloys coupled to a given dissimilar material are higher in 3·5% NaCl than in tapwater and distilled water where they are found to be comparable. In assessing galvanic corrosion behaviour of a given A1 alloy as a function of environment, one has to consider the effect of the dissimilar metal. The dissolution rate of A1 6061 is, for example, higher in tapwater with Cu as cathode than in 3·5% NaCl with SS304L or Ti-6A1-4V as cathode.     

NaCl液滴下304不锈钢表面电化学性质研究

利用丝束电极技术研究NaCl液滴下304不锈钢表面电化学参数分布及其随腐蚀时间的变化规律。结果表明,液滴下不锈钢丝束电极表面的腐蚀电位分布和电偶电流分布均呈现空间、时间上的不均匀性;丝束电极表面随机形成局部阴极区和阳极区,而且随着腐蚀时间的延长,局部区域的极性发生反转。液滴下电极表面的腐蚀程度和不均匀程度均随腐蚀时间的延长先增加后减小,在腐蚀12 h时达到最大。     

常用牺牲阳极合金在NaCl溶液中的接触腐蚀行为

研究了作为牺牲阳极材料的ＭｇＡｌＺｎＭｎ、ＡｌＺｎＩｎＳｉＭｇ和ＺｎＡｌＣｄ合金与Ａ３钢偶接时，溶液中Ｃｌ－浓度和电偶对中阴阳极面积比变化对三种合金接触腐蚀行为的影响。偶对阳极电偶电流密度ｊｇ随Ｃｌ－浓度增大而增大，ｊｇ与面积比成正比关系。偶对电偶电势Ｅｇ随Ｃｌ－浓度增大和面积比减小向负向变化。当偶对中阴极金属材料为３０２不锈钢和紫铜时，ｊｇ随Ｃｌ－浓度增大有不同的变化趋势。     

Probing of Atmospheric Corrosion of Metals: Carbon Steel

The methods of scanning vibrating capacitor (SVC, Kelvinprobe), IR microscopy (IRM), and galvanic current sensor are used in studying the atmospheric corrosion of carbon steel with locally applied NaCl. The SVC method is shown to give insight to the electrochemical heterogeneity of the surface. The distribution of cathodic and anodic domains is found by the IRM analysis of corrosion products. The passive surface of steel around the applied chloride takes part in the cathodic reaction of the corrosion process. The currents of the corrosion macrocell constituted by a chloride-covered anode domains and surrounding it cathodic area are measured by the sensor in humid air. From the areas of cathodic and anodic domains, the partial current ratio and the limiting stage of corrosion are found. The mechanism of galvanic couple formation and inhibition is discussed.     

Galvanic corrosion of bare and coated Al alloys coupled to stainless steel 304 or Ti-6Al-4V

The galvanic corrosion behavior of Al alloys 7075, 6061, 2024, bare or coated with the chemical conversion coating Alodine 600, coupled to stainless steel 304 or Ti-6Al-4V and immersed in aerated 3·5%NaCl solution, has been studied by continuous measurements of the galvanic current using a zero impedance ammeter and by weight loss measurements. Comparison of weight loss measurements for bare and coated uncoupled Al alloys shows that good corrosion protection is provided by the conversion coating. Data from weight loss and galvanic current measurements show that corrosion protection is also provided when coated Al alloys are coupled to stainless steel 304 or Ti-6Al-4V. Examination of potentiostatic polarization curves for the metals studied in 3·5%NaCl solution explains the protective action of the coating and also the higher dissolution rates of Al alloys coupled to stainless steel 304 instead of Ti-6Al-4V. Differences between dissolution rates calculated from galvanic current data and weight loss data are explained by theoretical considerations published recently by the authors taking into account the shapes of the individual polarization curves of the metals in the couple. After correction of galvanic current data, agreement between dissolution rates obtained by weight loss and galvanic current data is satisfactory. Continuous recording of the galvanic current reveals considerably more information than weight loss data.