Copper corrosion mitigation by binary inhibitor compositions of potassium sorbate and benzotriazole

This work presents the combined effect of two inhibitors, potassium sorbate (2,4-hexadienoic acid potassium salt) and 1,2,3-benzotriazole, on the corrosion behavior of copper in sulfate based solutions. Individual and combined characteristics of copper corrosion inhibition in sulfate solution in the presence of potassium sorbate (K-sorbate) and benzotriazole (BTAH) were studied with the use of electrochemical, microscopic and spectroscopic methods. Whereas, BTAH alone protects copper from corrosion attack in sulfate solutions only in a limited potential range below 0.4 V vs. saturated calomel electrode (SCE), the presence of K-sorbate combined with BTAH in such solutions enables the protection of the copper surface at potentials above 0.4 V_SCE. The mixture of both inhibitors provides supplementary and robust corrosion protection of Cu over a wide potential range.     

Effects of SRB on cathodic protection of Q235 steel in soils

The effects of sulfate reducing bacteria (SRB) on cathodic protection (CP) of the Q235 steel in the soils have been studied by bacterial analyses, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and energy‐dispersive X‐ray analysis (EDX). The results showed that the pH value of the soil around the steel gradually increased, the number of SRB and the corrosion rate of the steel decreased, and the CP efficiency increased with the increasing of applied cathodic potential. At the cathodic polarization potential of ?1050 mV, SRB still survived in the soils. At the same potential, the CP efficiency in the soil without SRB was higher than that with SRB, and the corrosion rate of the steel in the soil with SRB was much higher than that without SRB. The cathodic current density applied for the steel in the soil with SRB was bigger than that without SRB at the same cathodic potential.     

Corrosion rate of construction materials in hot phosphoric acid with the contribution of anodic polarization

The paper is focused on selection of a proper material for construction elements of water electrolysers, which make use of a 85% phosphoric acid as an electrolyte at temperature of 150 °C and which might be loaded with anodic polarization up to 2.5 V versus a saturated Ag/AgCl electrode (SSCE). Several grades of stainless steels were tested as well as tantalum, niobium, titanium, nickel alloys and silicon carbide. The corrosion rate was evaluated by means of mass loss at free corrosion potential as well as under various levels of polarization. The only corrosion resistant material in 85% phosphoric acid at 150 °C and at polarization of 2.5 V/SSCE is tantalum. In that case, even a gentle cathodic polarization is harmful in such an acidic environment. Hydrogen reduction leads to tantalum hydride formation, to loss of mechanical properties and to complete disintegration of the metal. Contrary to tantalum, titanium is free of any corrosion resistance in hot phosphoric acid. Its corrosion rate ranges from tens of millimetres to metres per year depending on temperature of the acid. Alloy bonded tantalum coating was recognized as an effective corrosion protection for both titanium and stainless steel. Its serviceability might be limited by slow dissolution of tantalum that is in order of units of mm/year.     

The electrochemical behavior of Sn–Ag binary alloys in sulfate solutions

The corrosion and passivation behavior of four binary xSn–Ag (x = 26, 50, 70, and 96.5 wt%) alloys and their pure metal components was investigated in sodium sulfate solutions using electrochemical techniques. The influence of two different electrolytic parameters, namely, concentration (0.01–1.0 M ) and pH (3.0–11.0) were studied while the specimens were potentiodynamically polarized between ?1000 and 500 mV versus saturated calomel electrode (SCE). The results showed that the corrosion current density (i_corr) increases with increasing either the tin content in the alloy or the ions concentration in the electrolyte. Increasing the pH value of a constant composition sulfate solution was found to improve the corrosion resistance of the tin‐richer alloys (x = 50–96.5 wt%), and decreases a little the stability of the silver‐rich one (74 wt% Ag). Impedance measurements at the free corrosion potential (E_corr) give good support for these results, where a small addition of tin to silver up to the intermetallic ratio (x = 26 wt%) gives an alloy with better corrosion resistance to the aggressive sulfate medium. In terms of the tin ratio, the order of surface film stability on the tested samples, generally follows the ranking: 26 > 96.5 > 50 > Ag > 70 > Sn. The good corrosion resistance of the tin‐rich alloy (x = 96.5 wt%), surpassing those for the pure constituents tin and silver can be attributed to the homogenous phase structure of this eutectic mixture.     

The corrosion behavior of 70/30 copper‐zinc alloy under the biofilm of sulfate‐reducing bacteria

A laboratory study was carried out on the effect of the biofilm of sulfate‐reducing bacteria (SRB), which plays an important role in corrosion of 70/30 copper‐zinc alloy in culture media under anaerobic condition. The API medium was used to culture the SRB in Zhongyuan oilfield. Potential/time measurement showed that the presence of SRB makes the corrosion potential more active with SRB growth metabolite. Electrochemical impedance spectroscopy (EIS) was used to analyse the electrode process of 70/30 Cu‐Zn alloy with SRB biofilm. Scanning electron microscopy (SEM) examinations revealed the formation of biofilm and corrosion products during exposure to SRB‐containing culture medium. X‐ray diffraction and EDS were used to analyse the corrosion products. The results show that the variation of activity of the SRB biofilm changes with SRB growth by the linear polarization resistance (R_p) and the EIS in culture medium inoculated SRB.     

铜钴镍离子对镁合金微弧氧化膜的影响

目的提高镁合金微弧氧化膜的耐蚀性。方法在Na_2SiO_3-NaOH-Na_2B_4O_7组成的电解液体系中,分别加入铜离子、钴离子和镍离子对AZ91D镁合金进行微弧氧化,研究离子种类和组成对膜层性能的影响。采用点滴实验测试膜层的耐蚀性,采用电化学工作站测试膜层的电化学性能,采用扫描电子显微镜(SEM)和能谱分析(EDS)对微弧氧化膜层的表面形貌和元素组成进行分析。结果电解溶液中加入钴离子、铜离子、镍离子后,镁合金微弧氧化膜的耐腐蚀性能均有提高。其中铜离子的影响最大,加入1.5 g/L的铜离子后,镁合金微弧氧化膜的点滴时间提高了77.3 s,膜层耐腐蚀性能显著提高。电化学测试结果得出,不加金属离子的氧化膜的腐蚀电流密度为1.092×10~(-5) A/cm~2,腐蚀电位为-1.487 V;加入钴、铜、镍离子浓度分别为2、1.5、3 mol/L时,腐蚀电流密度分别为3.912×10~(-6)、6.027×10~(-6)、2.167×10~(-6) A/cm~2,腐蚀电位分别为-1.412、-0.832、-1.047 V;加入金属离子制得的微弧氧化膜的腐蚀电流密度均降低了1个数量级,腐蚀电位不同程度地正移,其中加入铜离子后腐蚀电位提高了0.655 V。加入金属离子后,陶瓷膜表面空隙和孔洞数量不同程度地变浅和减少,增加了膜层的致密性和均匀性。结论电解液中添加一定量的铜、钴、镍离子均能够提高AZ91D镁合金微弧氧化膜层的耐蚀性,其中铜离子的效果最明显。     

一种控制腐蚀微生物的新方法--电化学杀菌

在厌氧条件下，用电化学方法和微生物学方法研究了金属腐蚀微生物硫酸盐还原菌(SRB)的电化学杀菌机制。循环伏安法表明，在外加电位为0．4V(SCE)附近SRB发生电化学氧化，出现了大小为10^-4A数量级的峰值电流。峰值电流分别随扫速和SRB培养时问的增加而有规律的变化。峰值电位的波动范围在50mV之内。在外加电位为0．4V，作用时间为10min时，SRB的存活率小于10％。电化学方法能杀死SRB是由于电极和吸附在电极表面的SRB细胞中的辅酶A(G0A)进行了电子交换，SRB发生电化学氧化而死亡。     

Einfluß sulfatreduzierender Bakterien auf den kathodischen Korrosionsschutz

Influence of sulfate-reducing bacteria on cathodic protection Sulfate-reducing bacteria (SRB) are frequently encountered at coating defects of cathodically protected pipes buried in soil. In laboratory experiments the corrosion behaviour of steel St 37 was studied at potentials in the range of ?0.5 V > U_Cu/CuSo4 > ?1.27 V and at the open circuit potential in the presence of a mixed culture containing SRB. For simulation of real conditions the experiments were performed on steel samples in sand columns through which a glucose-containing mineral salts solution was continuously pumped. On the basis of the corrosion rates determined an immediate corrosion risk was not evident for a homogeneous mixed electrode even at the open circuit potential. There was only an increase in protective current demand compared to sterile conditions. Hydrogen permeation through the low-alloy steel was slightly higher in the presence of SRB-containing mixed cultures than under sterile and H₂S-free conditions. The observed permeation current densities indicated that at potentials of U_Cu/CuSo4 < ?0.85 V hydrogen-induced corrosion damage was not to be expected under sulfate-reducing conditions.     

含硫酸盐还原菌土壤中阴极保护对Q235钢腐蚀的影响

利用交流阻抗测试技术、扫描电镜及表面能谱、微生物分析等方法，研究了阴极保护对土壤中Q235钢硫酸盐还原菌腐蚀的影响.30天的实验结果表明，在相同的阴极极化电位下，有菌土壤中Q235钢所需要的阴极极化电流密度均大于灭菌土壤，有菌土壤中Q235钢的平均腐蚀速率均大于灭菌土壤.随着阴极极化电位负移的增大，有菌及灭菌土壤中Q235钢试件周围土壤逐渐呈碱性，有菌土壤中Q235钢试件周围土壤中硫酸盐还原菌数量逐渐减少，当阴极极化电位为-1050 mV时，Q235钢试件周围土壤中硫酸盐还原菌仍能够存活.     

脱硫弧菌引起的铝的微生物腐蚀机理研究

目的揭示培养周期内脱硫弧菌(一种硫酸盐还原菌)引起的铝的微生物腐蚀机理。方法采用细胞计数、荧光显微镜、电子显微镜、X射线能谱仪以及电化学测试等技术,测试并分析铝在硫酸盐还原菌(SRB)培养基中的腐蚀行为和机理。结果培养初期,SRB没有引起铝的腐蚀速率加速。铝电极的线性极化电阻在SRB培养基中的值甚至高于无菌培养基。这是因为生物膜的累积阻碍了基体与溶液介质界面的电子传输。随着培养时间的延长,铝在SRB培养基中的腐蚀速率明显提高。培养7天时,铝电极在SRB培养基中的腐蚀电流比无菌培养基中高3个数量级。结论随着时间的延长,培养基中有机碳源等营养成分消耗过多,导致SRB无法从培养基中获得足够的营养源,进而转向从铝中获取自身呼吸作用所需的能量。同时,由于生物膜的覆盖导致膜下微环境的改变,局部酸性可能较大,进而加速了点蚀的形成。     

Microbiologically influenced corrosion of X60 carbon steel in CO2‐saturated oilfield flooding water

The corrosion behavior of X60 carbon steel in CO₂‐saturated oilfield flooding water inoculated with sulfate‐reducing bacteria (SRB) was investigated using polarization curves and electrochemical impedance spectroscopy (EIS). With the propagation of SRB in the flooding water, the pH values of flooding water increased quickly in the initial 2 days and remained relatively steady during the later stage. Polarization curves showed that the corrosion current density decreased during the first 10 days due to the protection of corrosion products and SRB‐biofilms, and then increased possibly due to the partial detachment of the corrosion products and the biofilms. EIS analysis also showed that the charge transfer resistance increased initially and then decreased with exposure time. In the beginning of corrosion, the anodic dissolution of X60 steel was dominated by CO₂. After the formation of SRB‐biofilms, part of FeCO₃ corrosion products was converted to incompact FeS precipitates by SRB bio‐mineralization. Thus, the dispersed iron sulfide in SRB‐biofilms and X60 steel base may constitute a galvanic couple, accelerating the localized corrosion of the steel base in the flooding water.     

Microbial Corrosion in Linepipe Steel Under the Influence of a Sulfate-Reducing Consortium Isolated from an Oil Field

This work investigates microbiologically influenced corrosion of API 5L X52 linepipe steel by a sulfate-reducing bacteria (SRB) consortium. The SRB consortium used in this study was cultivated from a sour oil well in Louisiana, USA. 16S rRNA gene sequence analysis indicated that the mixed bacterial consortium contained three phylotypes: members of Proteobacteria (Desulfomicrobium sp.), Firmicutes (Clostridium sp.), and Bacteroidetes (Anaerophaga sp.). The biofilm and the pits that developed with time were characterized using field emission scanning electron microscopy (FE-SEM). In addition, electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR) and open circuit potential (OCP) were used to analyze the corrosion behavior. Through circuit modeling, EIS results were used to interpret the physicoelectric interactions between the electrode, biofilm and solution interfaces. The results confirmed that extensive localized corrosion activity of SRB is due to a formed biofilm in conjunction with a porous iron sulfide layer on the metal surface. X-ray diffraction (XRD) revealed semiconductive corrosion products predominantly composed of a mixture of siderite (FeCO₃), iron sulfide (Fe _x S _y ), and iron (III) oxide-hydroxide (FeOOH) constituents in the corrosion products for the system exposed to the SRB consortium.     

The effects of sulfate reducing bacteria on corrosion of carbon steel Q235 under simulated disbonded coating by using electrochemical impedance spectroscopy

The effect of sulfate reducing bacteria (SRB) on the corrosion of the carbon steel Q235 has been investigated in the crevice under the simulated disbonded coating in the soil-extract solutions (SES). The results of electrochemical impedance spectroscopy (EIS) show that the corrosion rate is inhibited in the SES with SRB during the stationary phase of SRB, but enhanced during the death phase. The comparison of the polarization (R_p) and the charge transfer resistances (R_t) has indicated that the biofilm seriously influences the reactive procedure of metal/solution interface. SRB is found in the pits on the surface of the steel.     

硫酸盐还原菌对H68黄铜点蚀的影响

本文通过自腐蚀电位技术、交流阻抗技术以及动电位极化技术等电化学技术,研究了H68黄铜在硫酸盐还原菌中的腐蚀行为,并分析了硫酸盐还原菌的腐蚀机理和腐蚀特性.由实验结果得出,随着硫酸盐还原菌代谢活动的加强,铜电极的点蚀电位和开路电位具有一定的规律,并且H68黄铜的转移电荷呈现升降升的规律.在硫酸盐还原菌中的腐蚀行为比在无菌介质中强烈.硫酸盐还原菌代谢活动能降低溶液的pH值,破坏了铜电极表面的CuO的氧化膜,加速了铜电极的腐蚀,促进了金属的点蚀发生,使铜金属点蚀敏感性增加.     

采用丝束电极研究金属的缝隙腐蚀*

采用丝束电极研究了铜在5%NaCl介质中的缝隙腐蚀行为。研究表明,铜发生缝隙腐蚀的过程中,缝隙内金属的腐蚀电位分布是不均匀的,不均匀的程度相差达数十毫伏。在缝隙腐蚀的初期,缝隙内金属腐蚀电位随着缝隙腐蚀的发生逐渐正移。随着缝隙腐蚀程度的加深,缝隙内金属的腐蚀电位发生负移,且逐渐均匀分布。这一过程与经典的金属缝隙腐蚀机理相吻合。     

Electrochemical analysis of the microbiologically influenced corrosion of steels by sulfate-reducing bacteria

The differences between the general corrosion and microbiologically influenced corrosion (MIC) of steels were investigated in terms of its electrochemical behavior and surface phenomena. The corrosion potential of steels in the absence of SRB (sulfate-reducing bacteria) shifted to a negative value with the immersion time. However, the potential of the presence of SRB shifted to a positive value after 30 days' incubation, indicating the growth of SRB biofilms on the test metal specimens and the formation of corrosion products. In addition, the color of a medium inoculated with SRB changed from gray to black. The change in color appeared to be caused by the formation of pyrites (FeS) as a corrosion product, while no significant change in color was observed in a medium without SRB inoculation. Moreover, corrosion rates of various steels tested for MIC were higher compared to those of steels in the absence of SRB. In particular, the corrosion current density of TMCP steels in the presence of SRB was larger than that of other steels. Pitting corrosion was also observed at the surface of all steels in the SRB-inoculated medium. The pitting corrosion likely occurred due to SRB that was associated with the increasing corrosion rates through increasing cathodic reactions, which caused a reduction of sulfate to sulfide as well as the formation of an oxygen concentration cell.     

A mechanism of interaction of copper with a deoxygenated neutral aqueous solution

The electrochemical behaviour of Cu exposed to deoxygenated borate buffer for 330 h was characterised by chronopotentiometry, voltammetry, electrochemical impedance spectroscopy and cupric ion-selective electrode measurements. The results were interpreted by a quantitative kinetic model of the copper/electrolyte interface featuring two adsorbed intermediates produced by interaction of Cu with adsorbed water and electrochemical reduction of soluble divalent copper. The model reproduces successfully both the current vs. potential curve and the electrochemical impedance spectra around the open-circuit potential. On the basis of the experimental and calculation results, tentative conclusions for the interplay between hydrogen generation and copper corrosion are drawn.     

船用5052-O铝合金在海水中的力学和电化学性能(英文)

采用电化学实验和SEM表面形貌观察,对船用5052-O铝合金在海水中的腐蚀保护电位进行优化,以克服诸如点蚀、腐蚀、应力腐蚀开裂和氢脆等行为的发生。在外加电流阴极保护的条件下,最优的保护电位范围为-1.3V～-0.7V。在此电位下,试样的腐蚀电流密度较低,经恒电位实验后,试样表面形貌保持得较好。     

薄层液膜下金属电化学腐蚀电池的设计

设计了一种研究金属在薄层液膜下电化学行为的三电极腐蚀电池.该电池在降低研究电极和参比电极之间IR的同时消除了参比电极中离子对薄层液膜的污染,并且易于操作.通过稳态极化曲线和交流阻抗技术研究了该电池在薄层液膜下和在大量电解质溶液中的电化学行为,证明了该电池适合研究金属在大气中的电化学腐蚀行为.     

Growth characteristics of thermophile sulfate-reducing bacteria and its effect on carbon steel

Sulfate-reducing bacteria (SRB) have been identified as the main corrosive microorganisms causing unpredictable failure of materials. In this present work, a strain of thermophile SRB isolated from Bohai oilfield of China has been characterized and preliminarily identified. Furthermore, its effects on carbon steel at 60 °C in SRB culture media were studied by electrochemical methods such as potentiodynamic polarization and electrochemical impedance spectroscopy (EIS), and weight loss measurements. The results show that the bacteria belong to Desulfotomaculum. The optimum growth temperature and pH of the bacteria were 60 °C and 7.0, respectively. Weight loss measurements suggested that the corrosion rate of carbon steel in the culture media inoculated with thermophile SRB at 60 °C was 2.2 times less than that at 37 °C. At 60 °C, SRB shifted the freely corroding potential of carbon steel toward a more positive value in the first 10 days, which later change to a negative value. Results obtained from potentiodynamic polarization and EIS were in good agreement. The changes in biofilm structure with increase in bacteria supply offers some kind of protection to the base material in the early culture days at 60 °C. Subsequently, it accelerated corrosion. Energy dispersive spectrometry (EDS) and X-ray diffraction (XRD) methods indicate that corrosion products such as iron sulfides (FeS_x) in biofilm play an important role in the biocorrosion process.