The corrosion characteristics of reinforced steel in simulated concrete pore solutions with different amount of chloride ion and sulfate ion were investigated by means of polarization curves and electrochemical impedance spectroscopy. The results show that the corrosion rate of reinforced steel rose firstly and then declined with the increasing SO42- concentration in the solutions. The corrosion rate of the reinforced steel was the highest in a simulated sub-chloride saline soil solution (m(Cl-) / m(SO42-)=1.5). This suggested that addition of certain amount of SO42- can enhance the corrosion of reinforced steel. The corrosion rate of reinforced steel decreased gradually with the proportionally increasing amount of SO42- and Cl- in the solutions, which may be ascribed to the formation of a thick salt film on the steel surface and thereby lead to the increase of diffusion resistance for cathode process.
基于对制革工业园排污混凝土管破坏特征的现场调查和对混凝土的微观形貌及腐蚀产物的测试分析,探讨了污水对制革排污管混凝土的硫酸盐侵蚀破坏机理.结果表明,埋于地下的排污混凝土管,污水含有的硫酸盐对管内壁混凝土为半浸泡的盐侵蚀作用,内壁混凝土受化学腐蚀与物理侵蚀的双重复合作用.污水对管壁混凝土的化学腐蚀主要是低SO42-浓度下的钙矾石型侵蚀 (EA),碳硫硅钙石型硫酸盐侵蚀 (TSA),高钙硅比C-S-H凝胶向低钙硅比C-S-H凝胶转化,钙矾石和碳硫硅钙石向石膏转化等.物理结晶侵蚀劣化则与盐的种类,环境温湿度及变动情况,混凝土的渗透性等因素相关.
Deterioration process of concrete in salts crystallization zone of tannery sewage pipelines that half-buried (half-immersed) in sulfate solution environment was studied by examining the appearance and, microstructure and phase composition of the broken concrete sewage pipe, as well as the local environmental conditions, water quality analysis etc. It shows that concrete in salts crystallization regions that half-buried in sulfate solution environment is typically suffered from both of chemical corrosion and physical attack. The chemical corrosion processes includes the corrosion attacks of the formed products ettringite and thaumasite in low sulfate ion concentration, the transformation process of the C-S-H gel with high ratio of Ca to Si into depleted C-S-H gel, and the conversion process of ettringite and thaumasite into gypsum etc. The physical attack may be related to the type of salt species, temperature and humidity of environment, and the permeability of concrete.
采用三点弯曲实验研究应力比R对处于不同环境下的D36钢稳定裂纹扩展区疲劳裂纹扩展速率的影响.结果表明,空气中应力比对pairs区的疲劳裂纹扩展速率影响不大,然而海水环境中,在中等△K值范围内,应力比对裂纹扩展速率影响较空气中明显,且其裂纹扩展速率随着应力比的增加而增大.这种现象产生的原因是氢脆作用随着应力比的增大显著增强.通过三电极体系在f=1 Hz,R=0.1条件下分别对试件施加-400,-600,-800,-1000和-1200 mV的电极电位.结果表明,强阴极极化 (-1200 mV) 和阳极极化 (-400 mV) 在一定△K范围内会加速裂纹扩展,综合得出该条件下腐蚀疲劳的阴极保护电位为-800 mV.而应力比为0.3和0.5时施加-800 mV的电极电位对材料的保护作用减弱.
The effect of stress ratio R on the fatigue crack propagation rate (FCPR) of D36 steel was investigated in air and sea water with different applied potentials. The results reveal that by a given applied cyclic stress intensity △K in air, the da/dN-ΔK curve exhibits a slight change in fatigue crack propagation rate with the increase of stress ratio. However, by intermediate △K values, the increase of the fatigue crack propagation rate is obvious in sea water, which may be ascribed to the hydrogen embrittlement. With applied potentials with in a range from -400 to -1200 mV onto the test steels at f=1 Hz, R=0.1, it follows that with the potential corresponding toeither the over-cathodic protection (-1200 mV) or the anodic dissolution (-400 mV) conditions the corrosion fatigue crack propagation rate (CFCPR) will be accelerated within a certain △K range, and therewiththe optimal protection potential of -800 mV is identified. But the protection effect by the applied potential -800 mV was weakened with the increase of the stress ratio from 0.3 to 0.5.
针对安塞油田长2油井采出水中HCO3-及Cl-浓度相对较高造成的J55套管腐蚀穿孔严重的问题,利用动电位极化法和电化学阻抗法研究了温度,HCO3-和Cl-浓度对J55钢腐蚀行为的影响规律,利用扫描电镜 (SEM) 对比分析了45和80 ℃试片实验后的表面形貌.结果表明:温度,HCO3-和Cl-浓度对J55钢腐蚀的影响规律相似,分别在温度为80 ℃时,HCO3-浓度为7 g/L和Cl-浓度为10 g/L时出现腐蚀速率的极大值,使腐蚀电流最大和电荷转移电阻最小;HCO3-浓度不小于5 g/L时,J55钢阳极极化曲线出现钝化;温度不小于60 ℃和HCO3ˉ浓度不小于5 g/L时,电化学阻抗谱出现Warburg阻抗,并且Warburg阻抗随HCO3-浓度变化较大,随温度变化较小;80 ℃时试片表面的腐蚀产物膜较45 ℃时更厚且均匀.
The concentration of HCO3- and Cl- in oil well produced water of Ansai oilfield Layer 2 are relatively higher, causing problems of local corrosion and serious perforation of J55 casing pipeline. Effect of temperature, HCO3- and Cl- on corrosion behavior of J55 steel in the oil well produced water was studied by using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The corrosion morphology of J55 samples tested at 45 and 80 ℃ was examined by SEM. The results showed that temperature, HCO3- and Cl- exhibit similar effect on the corrosion of J55 steel, the corrosion rate of J55 steel exhibits a maximum, correspondingly a maximum of corrosion current and a minimum of the charge transfer resistance when the temperature is 80 ℃, the concentration of HCO3- is 7 g/L and the concentration of Cl- is 10 g/L respectively. Besides, passivation occurred during anodic polarization when the concentration of HCO3- is greater than or equal to 5 g/L. There were Warburg impedance when the concentration of HCO3- is greater than or equal to 5 g/L and the temperature is greater than or equal to 60 ℃ respectively. The Warburg impedance changed largely with the change of concentration of HCO3-, but less with the change of temperature. The corrosion product film is thicker and more uniform at 80 ℃ rather than at 45 ℃.
通过周期浸润加速腐蚀实验,研究了不同Ni含量的耐候钢在模拟海洋大气环境下的腐蚀规律.采用失重法评价耐候钢的耐蚀性,并利用扫描电镜 (SEM),X射线衍射(XRD) 和电化学方法对耐候钢表面生成的锈层进行了分析.结果表明,随着Ni含量的增加实验钢的耐蚀性逐渐增加,当Ni含量超过3%(质量分数) 其耐蚀性较对比钢提高了两倍;Ni的存在能够提高实验钢的自腐蚀电位,并促进保护性腐蚀产物α-FeOOH的形成;电化学阻抗测试结果表明,实验钢中Ni含量越多,实验钢的电阻越大,锈层的保护性越好.
Corrosion behavior of weathering steels with different nickel content was studied by wet/dry cyclic test. The mass loss method was used to evaluate the weatherability of weathering steel, while the rust layers formed on weathering steel were characterized by using SEM, XRD and electrochemical measurements. The result indicates that the higher Ni content,the better corrosion resistance the steel is. The corrosion resistance of the steels with Ni content above 3%(mass fraction) are about twice of the counterpart steel without Ni. The addition of Ni enhances the free corrosion potential of the steel and promotes the formation of α-FeOOH, so as to improve the protectiveness of the formed rust. The EIS results indicate that with the increasing Ni content of the steels, the impedance of the rust layer becomes bigger.
为进一步提高铝合金阳极氧化膜的耐蚀性能,采用磷酸盐对其进行封孔处理.利用电化学阻抗谱 (EIS ) 分析该封孔处理对阳极氧化膜耐蚀性能的影响规律,并与常规沸水封孔和铈盐封孔进行比较.实验结果表明,磷酸盐封孔处理后可在阳极氧化膜表面形成约为15 μm厚的致密磷酸盐涂层,与常规沸水和铈盐封孔处理相比,磷酸盐封孔处理的阳极氧化膜具有更好耐蚀性和时效性.该方法可为阳极氧化膜封孔处理提供一种新途径.
Anodic oxide films on Al-alloys were sealed by aluminum phosphate to further improve their corrosion resistance. Electrochemical impedance spectroscope (EIS) was used to study the effect of the sealing treatment on corrosion resistance of the anodic oxide films in comparison with those sealed with boiling water and cerium salt solution respectively. The results showed that, the aluminum phosphate coating was formed on the anodic oxide film sealed with aluminum phosphate, and it could provide the anodic oxide film the best corrosion resistance superior to those sealed with boiling water and cerium salt solution. Furthermore, the effectiveness of the aluminum phosphate treatment could last longer than that of sealing treatmants with boling water and cerium salt solution. This method could be a new sealing treatment for anodic oxide film on Al-alloys.
研究了NaHCO3+NaCl碱性溶液中,较宽Cl-浓度 (0.001~0.3 mol/L) 范围内Cl-浓度及HCO3-和Cl-的浓度比值 ([HCO3-]/[Cl-]) 对Q235碳钢小孔腐蚀电位的影响.结果表明,Cl-浓度较大 (>0.02 mol/L) 时,碳钢的稳定孔蚀电位Eb和亚稳态孔蚀电位Em都与[HCO3-]/[Cl-]符合很好的线性关系,[HCO3-]/[Cl-]升高Eb和Em线性增大;当Cl-浓度较小 (<0.02 mol/L) 时,Eb和Em与[HCO3-]/[Cl-]之间不存在良好的线性关系,该条件下碳钢表面在发生稳定孔蚀前观察不到微米级的亚稳态小孔.
The influence of Cl- concentration and the concentration ratio of HCO3- to Cl- ([HCO3-]/[Cl-]) in NaHCO3+NaCl alkaline solution on the pitting potentials of Q235 carbon steel was studied in a chloride ion concentration range from 0.001 to 0.3 mol/L. It was found that when the Cl- concentration is higher than 0.02 mol/L, good linear relationship exists not only between the pitting potential Eb and [HCO3-]/[Cl-] but also between the meatstable pitting potential Em and [HCO3-]/[Cl-], that is Eb and Em increase linearly with the increase of [HCO3-]/[Cl-]. When the Cl- concentration is lower than 0.02 mol/L, [HCO3-]/[Cl-] is not linear with Eb and Em, and under these conditions, no micron scale metastable pits can be observed on the steel surface before the occurence of stable pits.
针对P110钢在模拟油田采出水中发生的严重腐蚀情况,采用一种双季铵盐类复配缓蚀剂对其进行腐蚀防护.通过失重挂片法,电化学频率调制技术和耦合多电极技术评价该缓蚀剂的缓蚀性能.结果表明,该缓蚀剂能够有效地抑制P110钢的腐蚀,在60 ℃,当复配缓蚀剂的浓度为150 mg/L时,缓蚀率达到95.31%,在90 ℃时虽然缓蚀率不高,但是能够有效的抑制局部腐蚀.电化学频率调制技术 (EFM) 和耦合多电极矩阵传感器(CMAS) 均能够用于监测金属的腐蚀情况,评价缓蚀剂的缓蚀性能.通过EFM校验因子能够清楚地表明该缓蚀剂对局部腐蚀的抑制效果,而通过CMAS表明,缓蚀剂在金属表面上的吸附能够有效地消除金属表面上存在的阴极点和阳极点,从而抑制金属的局部腐蚀.
Inhibition performance of a complex inhibitor of bis-quaternary ammonium and thiourea (with mass fraction 1∶1) for the serious corrosion of P110 steel in simulated oilfield produced waters was studied by means of techniques of mass loss, electrochemical frequency modulation (EFM) and coupled multielectrode array sensors (CMAS). Experimental results indicate that this inhibitor could inhibit P110 steel from CO2 corrosion efficiently. The inhibition efficiency was up to 95.31% when the concentration of inhibitor was 150 mg/L at 60 ℃. The inhibition efficiency decreased at 90 ℃, however, the inhibitor could eliminate the pitting corrosion of P110 efficaciously. EFM and CMAS techniques could monitor the corrosion process of the steel and evaluate the effectiveness of the inhibitor. The deviation from theoretical value of causality factor of EFM could reveal the effectiveness of the addition of inhibitor, i.e. the inhibitor could protect P110 from pitting corrosion. The results of CMAS showed that the prevention of pitting corrosion could be attributed to the adsorbing of inhibitor on the steel surface to relieve the concentrated distribution of cathodic and anodic currents.
采用慢应变速率拉伸实验方法 (SSRT) 结合断口扫描电镜 (SEM) 观察,研究了阴极保护电位对E550钢在海水中氢脆敏感性的影响.结果表明:随着阴极保护电位负移,E550钢在海水中的氢脆敏感性增加,阴极保护电位为-0.95 V (vs SCE) 时,拉伸试样出现脆性解理断裂特征,电位为-1.05 V时,E550钢断口呈明显脆性断裂特征.
The susceptibility to hydrogen embrittlement (HE) of E550 steel was investigated in seawater by means of slow strain rate test and SEM observation of fractured surfaces. The results showed that the susceptibility to hydrogen embrittlement increased with the decrease of cathodic protection potential. The fracture surface of the steel after slow strain rate test exhibited cleavage brittle fracture at -0.95 V (vs SCE). In general, E550 steel was subject to HE in sea water at -1.05 V.
选用了正硅酸四乙酯和硅烷偶联剂KH-550两种材料对铜锌合金粉进行表面改性,通过扫描电镜,热分析仪,红外光谱仪等仪器表征其抗氧化性和红外消光能力.结果表明,铜锌合金粉及其改性物的氧化放热峰温 (Tp) 分别为332.2,330.1和302.3 ℃,增重率分别为16.5%,13.7%和14.6%.在3~5 μm,两种改性物的质量消光系数 (αλ) 分别为0.82和0.63 m2/g;在8~14 μm,αλ值分别为0.69和0.53 m2/g.与纯铜锌合金粉相比,改性物的红外消光能力下降有限,抗氧化性提高.
In order to improve the anti-oxidation performance of bronze powder, two kinds of materials i.e. tetraethyl orthosilicate and silane coupling agent KH-550 were used to coat the bronze powder. Then their oxidation resistance and IR extinction performance were characterized by scanning electron microscopy (SEM), thermal analyzer and infrared spectrometer. Results show that oxidation exothermic temperatures (Tp) of the bronze powder without and with coatings are 332.2, 330.1 and 302.3 ℃ respectively, correspondingly their weight gain rate are 16.5%, 13.7% and 14.6% respectively. In 3~5 μm bands, quality extinction coefficient of the two coated powders (αλ) are 0.82 and 0.63 m2/g; while in 8~14 μm, the values of αλ are 0.69 and 0.53 m2/g. Compared with pure bronze powder, the infrared extinction ability of the two coated bronze powders is dropped little while their oxidation resistance is enhanced.
某风场1.5 MW风电机组齿轮箱中速轴小齿轮失效.该齿轮箱设计寿命20 a,实际使用了5 a.齿轮的材质是20CrNiMo,齿面经过渗碳淬火.采用宏观观察,微观观察和断口分析并结合其它理化测试,分析了小齿轮失效的原因.现场宏观观察发现,大部分轮齿相对完好,只有两支轮齿失效,其中一支齿面剥落,另一支齿面硬化层开裂.经分析,齿面剥落和齿面开裂的原因相同.导致齿轮失效的原因是:齿面粗糙度较大,较深的加工刀痕在异常冲击载荷的作用下造成齿面开裂,随后在循环工作载荷的作用下,萌生了疲劳裂纹并不断扩展,最终导致齿面硬化层脱落.建议提高齿轮表面加工质量,降低表面粗糙度,同时改进齿轮箱制动技术,避免异常载荷冲击造成齿面过载.
Flakes fell from the tooth surface of the small gear in the gearbox of a 1.5 MW wind turbine in service. The design lifetime of the gear is 20 a. However, it failed 5 a later since it was installed into the gearbox. The material is 20CrNiMo and the gear was carburized and quenched during the manufacturing process. Macro- and micro-observation of the fracture surface as well as some necessary physical and chemical analysis were applied to analyze the cause for the failure of the small gear. Besides, results from the macro-observation showed that only two teeth failed, on the one of which flakes fell from the tooth surface only left some pits, and on the other tooth surface some cracks can be observed obviously. The results also showed that pits and cracks could be attributed to the same reason. Tool marks on the tooth surface increases the risk of cracking. In addition, the abnormal load introduced by emergency braking led to cracks occurred along the machining marks on the tooth surface. Then, fatigue cracks nucleated at the tip of the crack and extend slowly driven by the working load. Finally, the hardened layer fell from the tooth surface and left some pits. It was suggested that the machining quality and the braking technology should be improved in order to avoid the cracking of the teeth surface under the abnormal impact load.