Cathodic protection of XL 52 steel under the influence of sulfate reducing bacteria

The effect of sulfate reducing bacteria (SRB) upon the cathodic protection of XL 52 steel was determined, in order to identify if the potential value of ?0.950 V versus copper/copper sulfate electrode is good enough to protect the metal surface. During the experiments, different operational parameters were monitored: hydrogen sulfide production, iron concentration, electrolyte alkalinity, microorganisms' population, as well as the metal surface damage. At the same time, the corrosion rate was determined using two electrochemical techniques: polarization resistance (PR) and electrochemical impedance spectroscopy (EIS). According to the results, it was observed that the protection potential of ?0.950 V versus copper/copper sulfate electrode is not enough to control the microbiologically induced corrosion. This situation is reinforced by the fact that significant iron concentration was found in the electrolyte. The microbiological activity is not affected by the protection potential. On the contrary, the population growth is slightly strengthened. The alkalinity generated by the applied potential did not stop the SRB growth. A type of localized corrosion was developed during the experiments with microorganisms, even when the protection potential was applied to the system.     

海水及培养基中假单胞菌对45钢电化学腐蚀行为的影响

采用微生物分析、失重法、自腐蚀电位、EIS、动电位极化曲线和SEM等手段对比研究了45钢在无菌海水、无菌培养基、假单胞菌海水和假单胞菌培养基4种不同环境下的腐蚀行为。结果表明：腐蚀初期假单胞菌及培养基均对45钢有缓蚀作用。但随着时间的推移,假单胞菌新陈代谢作用引起了氧浓差腐蚀,且其代谢产物中的碱及铁载体的局部堆积加速了45钢的腐蚀。培养基环境对微生物腐蚀有促进作用。     

模拟油气田环境中HP13Cr和N80油管钢的CO_2腐蚀行为

采用电化学方法研究了HP13Cr和N80油管钢在含饱和CO_2的NaCl溶液中的腐蚀行为,结果表明,HP13Cr钢自腐蚀电位较N80钢低,自腐蚀电流密度较N80钢高;与N80钢相比,HP13Cr钢极化曲线的循环滞后环面积小,点蚀发生的程度低;HP13Cr钢的极化电阻高于N80钢的极化电阻,说明HP13Cr抗CO_2腐蚀能力强;当HP13Cr与N80组成电偶对时,两者的电偶电位均较其自腐蚀电位负移,且因电偶电流较大而不能偶接使用。     

Study of the electrochemical behaviour of 304 stainless steel in postgate medium in the presence and absence of desulfovibrio desulfuricans

A comparative study has been undertaken on the behaviour of AISI 304 steel in Postgate medium with and without the presence of Desulfovibrio desulfuricans subspecies desulfuricans bacteria (strain DSM 642). Electrochemical studies were carried out with open circuit potential measurements, linear polarization, electrochemical impedance spectroscopy (EIS) and scanning electronic microscopy (SEM). In Postgate medium without bacteria, and as expected in stainless steels, the formation is observed of a protective surface passive film on the AISI 304 steel. On measuring the corrosion potentials (E_corr), it is noted that the potential tends to rise with the immersion time, and in the impedance graphs an increase is observed in the charge transfer resistance and a higher phase angle with respect to the other systems tested. However, in Postgate medium with Desulfovibrio desulfuricans (strain DSM 642), the tendency of the corrosion potentials (E_corr) is not uniform, though the recorded values are less noble than those for the medium without bacteria. A variation is observed in the properties of the layer of corrosion products in the presence of bacteria as the immersion time advances (due to the effects caused by the formation of corrosion products which gives rise to changes in the corrosion speed).     

SiC_p/2024Al铝基复合材料的耐蚀性

用电化学方法和浸泡试验研究了SiC颗粒粒度和体积分数对SiCp/ 2 0 2 4Al铝基复合材料在 3.5 %NaCl水溶液中耐蚀性的影响 ,作为比较对 2 0 2 4Al的耐蚀性也进行了研究。结果表明 ,与基体相比 ,SiCp/ 2 0 2 4Al复合材料并不增加点蚀敏感性 ,其抗蚀性与SiC体积分数和粒度有关 ,SiC颗粒体积分数低或粒度高的复合材料 ,其抗蚀性往往大。     

SiC/钢双连续相复合材料在NaCl溶液中的腐蚀行为

利用失重试验和电化学方法研究了泡沫SiC/钢双连续相复合材料在3.5%NaCl水溶液中的腐蚀行为.结果表明:多孔SiC增强体的存在对泡沫SiC/钢双连续相复合材料的腐蚀性能有一定程度的影响,其腐蚀敏感性比基体20钢稍大,这是由于基体与SiC之间的大量界面导致复合材料耐蚀性的降低,但界面处形成的金属间化合物提高了复合材料的耐蚀性.泡沫SiC增强体筋结构对其腐蚀行为有较大影响.选用致密骨架制备的复合材料的耐蚀性明显不如纯基体(45钢),主要原因是Fe与致密SiC骨架间存在电偶腐蚀倾向.     

磁化水对金属耐蚀性能的影响

水的磁化处理在工业水处理中的应用日益广泛,但磁化水对不同金属耐蚀性能的影响不同。采用极化曲线和电化学阻抗谱研究了300℃条件下模拟锅炉水(pH=9.0)中磁化处理对20G钢及316L不锈钢耐蚀性能的影响。结果表明,模拟锅炉水经磁化处理可提高20G钢的阻抗值,降低其腐蚀电流密度;而对316L不锈钢,溶液经磁化处理使不锈钢电极的阻抗值减小,钝态电流密度增大。说明模拟锅炉水经磁化处理可以提高20G钢的耐蚀性能,但却降低了316L不锈钢的耐蚀性。     

Corrosion properties of plasma-polymerized methylcyclohexane films using electrochemical methods

Three types of methylcyclohexane (MCH) coating were deposited as interlayer dielectrics on copper using plasma-enhanced chemical vapor deposition (PECVD) at three different RF plasma power levels. The coating performance was then evaluated by an electrochemical im pedance spectroscopy (EIS) and a potentiodynamic polarization test in 3.5 wt.% NaCl solution. An atomic force microscopy (AFM) and Fourier transform infrared reflection (FT-IR) spectroscopy were also conducted to analyze the coatings. The MCH coatings showed a lower corrosion rate than the copper substrate in the potentiodynamic tests. The EIS results showed that the corrosion resistance of the coatings increased with an increasing plasma power. Thus, the MCH films with an increasing plasma power improved the corrosion resistance due to the formation of a low-porosity coating, the enhanced formation of C−H, C−C, and C≡C stretching configurations, and the improved smooth surfaces.     

LaFe11.6Si1.4合金在水溶液中的缓蚀

利用电化学技术以及表面形貌分析对LaFe11.6Si1.4合金在水溶液中的缓蚀进行研究。结果显示,不同浓度的Na2WO4以及低浓度的NaH2PO4溶液对合金均有显著的缓蚀作用。这主要是由于加入缓蚀剂后,材料的阳极溶解反应被有效抑制,并且在低浓度下由于缓慢的扩散过程阻碍了反应的进行,从而最终抑制腐蚀的发生。     

Corrosion behaviour and mechanism of 6082 aluminium alloy in NaCl and Na2SO4 etchants

The corrosion behaviour of 6082 aluminium alloy was studied by measuring the electrochemical impedance spectra and electrode polarization curves. After the electrochemical tests, a microstructural analysis of the samples was conducted by using optical microscopy and electron scanning microscopy techniques to determine the corrosion mechanism. The results show that the Nyquist plot of the electrochemical impedance data in the NaCl solution consists of high- and low-frequency capacitive impedance loops. When ions are added to the NaCl etchant, the Nyquist plots of the electrochemical impedance data are composed of two different curves: a high-frequency capacitive impedance loop and a low-frequency inductive impedance loop. The corrosion current density increases with increasing concentration, and as a result, the corrosion resistance of the aluminium alloy decreases. The microstructures of 6082 aluminium alloy consist of Mg₂Si secondary particles in a large α-Al matrix. Pitting corrosion initially occurs at the boundary between the matrix and secondary particles because the electrode potentials of the matrix and secondary particles are different. Then, corrosion paths develop along the network-like grain boundaries, and finally, massive network-like corrosion occurs throughout the entire alloy.     

Comparison of electrochemical techniques during the corrosion of X52 pipeline steel in the presence of sulfate reducing bacteria (SRB)

This work compares three electrochemical techniques, linear polarization resistance (LPR), electrochemical impedance spectroscopy (EIS) and electrochemical noise (EN), used in the study of corrosion of X52 steel samples in an environment containing a culture of sulfate reducing bacteria (SRB). The study emphasizes the different electrochemical information obtained when using these techniques in microbiologically influenced corrosion (MIC) studies.     

热镀锌钢表面乙烯基三乙氧基硅烷膜的腐蚀电化学行为

采用开路电位(OCP)、交流阻抗(EIS)和动电位极化法对热镀锌钢表面乙烯基三乙氧基硅烷膜腐蚀电化学行为进行了研究。结果表明,在3.5%NaCl溶液中,涂覆硅烷膜层的热镀锌钢与空白热镀锌钢相比,其低频阻抗值提高至少2个数量级,同时腐蚀电流密度减小1个数量级以上,乙烯基三乙氧基硅烷膜防腐蚀效果良好。     

Corrosion behaviors of carbon steel induced by life activities of Phaeodactylum tricornutum in a marine environment

Microbiologically influenced corrosion induced by bacteria has been studied for many years. Corrosion is known to be sensitive to the presence of microalgae, such as Phaeodactylum tricornutum. However, the life activity of P. tricornutum that influences the general and localized corrosion of carbon steel is not fully understood. The current study uses a combination of immersion tests and electrochemical experiments with a detailed surface characterization to reveal the naturally formed corrosion products with/without the presence of P. tricornutum. The results show that samples suffer from pitting corrosion and the averaged pit depths are approximately 15 μm under a light–dark cycle condition or a 24-h constant light condition. Meanwhile, the corrosion products are mainly comprised of γ-FeOOH and Fe₃O₄ in a constant light condition. However, γ-FeOOH, Fe₃O₄, and FeCO₃ are found in a light–dark cycle. This study proposes the fundamental mechanisms of the effect of P. tricornutum life activities on the corrosion performance of Q235 carbon steel, to fulfill the knowledge gaps of the presence of microalgae inducing the general and pitting corrosion of carbon steel.     

前处理对化学转化处理铝锂合金耐蚀性的影响

采用手工脱氧、打磨脱氧、浸渍脱氧三种不同的前处理工艺对新型2198铝锂合金进行前处理,之后手工刷涂Alodine1200s化学处理液进行化学转化处理。通过极化曲线和交流阻抗谱,研究了所得试样在3.5%NaCl溶液中的腐蚀行为,并结合微观形貌分析,研究了前处理方式对试样耐蚀性的影响。结果表明:打磨脱氧前处理的试样击穿电位最正,自腐蚀电流密度最低,容抗弧半径最大,阻抗模值最大,低频段阻抗相位角最接近于-90°,耐蚀性最好。     

Corrosion behaviour of stainless steel exposed to highly concentrated chloride solutions

The characteristics of pitting corrosion of Type 304L stainless steel (SS) exposed to highly concentrated chloride solutions were studied through the evaluation of the corrosion potential, the pitting potential, the structure of the passive layer and the statistics of pitting depth and density. Both as-received and weld metal samples were studied. The weld metal sample was machined from the welding zone of a butt weld of Type 304L SS. The results showed an accelerated anodic dissolution and depressed film resistance at the welding zone, but no dramatic change on pitting corrosion was observed from the statistics of pitting during the test duration up to 720?h. The pitting corrosion resistance was significantly affected by the chloride concentration and slightly affected by the temperature under the investigated conditions.     

电化学阻抗谱研究三种涂层体系的耐蚀性

为选择某型特种装备的表面防腐蚀涂层,利用电化学阻抗谱对H06-4环氧富锌/H53-13环氧云铁/丙烯酸聚氨脂、环氧富锌/厚膜灰云铁环氧/TB06-42丙烯酸聚氨脂和环氧防锈平整底漆/CE-46环氧/丙烯酸聚氨脂三种涂层体系进行了耐蚀性评价测试。结果表明,随着浸泡时间的延长,三种涂层体系的保护作用都降低。对比涂层的阻抗谱变化特征得知,H06-4环氧富锌/H53-13环氧云铁/丙烯酸聚氨脂涂层体系耐蚀性较佳,因此被选为某型装备用防腐蚀涂层。     

Corrosion resistance of Mg-Mn-Ce magnesium alloy modified by polymer plating

Polymeric nano-film on the surface of Mg-Mn-Ce magnesium alloy was fabricated by polymer plating of 6-dihexylamino-1,3,5-triazine-2,4-dithiol monosodium(DHN) to improve its corrosion resistance.The electrochemical reaction process was analyzed by cyclic voltammetry and two obvious peaks of oxidation reaction were observed.The static contact angle of distilled water on polymer-plated surface can be up to 106.3°while on the blank surface it is 45.8°.Potentiodynamic polarization results show that the polyme...     

Electrochemical corrosion response of a precipitation hardening moulds steel in a NaCl solution

Investigations concerning the electrochemical corrosion behavior of mould steels are scarce and limited. In the present study, the corrosion resistance of a precipitation hardening moulds steel submitted to aging treatments has been assessed in a 0.1 M NaCl aqueous solution by means of potentiodynamic polarization and electrochemical impedance spectroscopy measurements. The electrochemical characterization of the steel not submitted to hardening treatments was also examined and a comparative study was made between the different specimens. Scanning electron microscopy and electron probe microanalysis were used to obtain information about the morphology and chemical composition of the steels surface after the electrochemical tests. Increasing the aging temperature an increase of secondary hardness is observed, attributable to an increase of secondary phases (re‐precipitated carbides and metastable GP zones) amount, positively reflecting on the mechanical properties. However, the electrochemical results show a progressive worsening of the corrosion behavior, the as‐received steel sample exhibiting the best corrosion resistance. The observed decrease of corrosion resistance with increasing the aging temperature is ascribed to enhanced galvanic coupling phenomena between the secondary phases, acting as cathodes, and the surrounding matrix which, consequently, experiences preferential dissolution.