Electrochemical corrosion behavior of 300M ultra high strength steel in chloride containing environment

The electrochemical corrosion behavior of 300M ultra high strength steel in chloride containing environment was investigated by potentiodynamic polarization technique, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The results show that uniform corrosion occurs on 300M steel during the electrochemical measurements because no anodic passivation phenomenon is observed on polarization curves within the measurement range. The tests also show that 300M steel is highly susceptible to chloride containing solution, which is characterized by corrosion current density increasing with the addition of chlorides, and corrosion potential shifting towards positive direction and corrosion resistance decreasing, positively suggesting that chloride ions speed up the corrosion rate of 300M steel. Meanwhile corrosion products on the 300M steel surface formed during the salt spray test are too loose and porous to effectively slow down the corrosion rate. Additionally, a schematic structure of uniform corrosion mechanism can explain that 300M steel has better property of stress corrosion cracking (SCC) resistance than stainless steels.     

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.     

碳钢在两种氯化物溶液中的极化行为

利用极化试验和交流阻抗试验研究了碳钢在0.5MNH4Cl和0.5MNaCl溶液中的点蚀行为;通过金相显微镜和电子探针对钢的腐蚀形貌进行观察。结果表明:碳钢在0.5MNaCl和0.5MNH4Cl溶液中的极化曲线都出现活化特征。随着溶液pH值的增加和NaHCO3的添加,碳钢在NH4Cl和NaCl溶液中极化曲线上均有活化、活化-钝化转变、钝化和点蚀特征。显微观察表明,钢中的夹杂物是主要的点蚀诱发源。碳钢在0.5MNaCl和0.5MNH4Cl溶液中形成的活化峰分别与形成沉积膜和络合物有关。     

镀锌层破损汽车钢板的腐蚀行为研究

采用稀盐酸溶解汽车板部分镀锌层,研究了镀层破损率不同试样在5%NaCl溶液中的腐蚀行为,并对腐蚀产物形貌进行了观察。结果表明：在腐蚀初期,镀锌层试样的腐蚀速率高于基板,镀层的消耗对试样失重起主要贡献;试样的整体腐蚀速率随镀层破损率的增加而增大,且随腐蚀时间的延长而有所下降;采用电偶腐蚀电位、电化学阻抗谱(EIS)和动态极化等测量方法研究了镀层破损双相耦合电极的腐蚀电化学特性,所得结果基本一致。     

Application of EIS and SEM to evaluate the influence of pigment shape and content in ZRP formulations on the corrosion prevention of naval steel

The effects of pigment volume concentration and morphology of zinc particles employed in the formulation of zinc rich paints (ZRP) suitable for the corrosion protection of naval steel in sea water, have been investigated using electrochemical impedance spectroscopy combined with open circuit potential measurements and SEM micrograph analysis. Different ZRP samples were tested during exposure to artificial sea water for up to 70 days. The characteristics and properties of the naval steel/ZRP coating/sea water systems were determined from an impedance transfer function model which involves the reactions occurring at the metal/ZRP and ZRP/solution interfaces as well as diffusion processes through the active ZRP coating. Information concerning the influence of concentration and shape of the zinc pigment on the corrosion protective behaviour of ZRP coatings and on the exposure time dependence of the system parameters allowed to interprete the form in which the galvanic action and the barrier effect diminish progressively. The degree of rusting of the steel substrates as well as the blistering resistance of the formulated ZRP have been also evaluated according to conventional ASTM standards.     

Electrochemical corrosion behaviour of innovative mould steels in a chloride‐containing environment

Investigations concerning the electrochemical corrosion behaviour of mould steels are scarce and limited. In the present study the corrosion resistance of an innovative mould steel (a microalloyed steel, steel 2), devoted to the fabrication of large size moulds, and a steel having the same composition without microalloying elements (B, Zr, Nb, steel 3), proposed for small size moulds, was assessed in a chloride‐containing environment and compared with that of the traditional 1.2738 steel. Potentiodynamic polarization and electrochemical impedance spectroscopy measurements were carried out on the investigated steel samples in a 0.1 M NaCl solution at 25 °C. Scanning electron microscopy and electron probe microanalysis were used to characterize the specimens surface after the electrochemical tests. Despite having a bainitic microstructure, the electrochemical corrosion behaviour of the investigated steels is quite different. Results showed that the steel 3 and the 1.2738 steel samples exhibit the best and the worst electrochemical corrosion behaviours compared to the steel 2 sample. The presence of pearlite is considered as the main reason for the poor corrosion behaviour showed by the 1.2738 steel sample, due to galvanic coupling phenomena between this phase and the bainitic matrix which experiences preferential dissolution. The coarse bainitic microstructure characterizing the steel 2 sample is responsible for its lower corrosion resistance as compared with the steel 3 sample exhibiting a finer bainitic microstructure.     

Micro‐electrochemical characterization of galvanic corrosion of TA2/316L composite plate

Galvanic corrosion behavior of TA2/316L composite plate was investigated in the solution of 3.5 wt% NaCl by galvanic potential monitoring, scanning localized electrochemical impedance spectroscopy (LEIS) and scanning vibrating micro‐electrode (SVME) techniques. The results demonstrated that the pitting corrosion resistance of 316L for the galvanic combination sample is lower, and the coupled current density is higher than for the single 316L sample. It indicates that the galvanic action works on the corrosion behavior of the TA2 titanium alloy/316L stainless steel galvanic combination in sodium chloride solution. The galvanic effect width was determined as 1500 µm.     

Electrochemical corrosion behavior of a novel antibacterial stainless steel

A novel antibacterial stainless steel (ASS) with martenstic microstructure has been recently developed, by controlled copper ion implantation, as a new functional material having broad-spectrum antibacterial properties. The electrochemical corrosion behavior of the ASS in 0.05 mol/L NaCl was assessed using linear polarization and electrochemical impedance spectroscopy (EIS) and compared with that of a conventional stainless steel (SS) without copper ion implantation. The ASS exhibited higher corrosion susceptibility in the chloride medium; with a more negative (active) corrosion potential, higher anodic current density and lower charge transfer and polarization resistance. This has been attributed to the occurrence of copper-catalyzed interfacial reactions. A functional tool, 3-D presentation of EIS data, has been employed in analyzing the electrochemical corrosion processes as well as probing complex interfacial phenomena.     

Electrochemical corrosion behaviour of a Ti‐IF steel and a SAE 1020 steel in a 0.5 M NaCl solution

Investigations concerning the electrochemical corrosion behaviour of low carbon (LC) and ultra‐low carbon (ULC) steels are relatively scarce and limited. The present study aims to compare electrochemical impedance parameters and potentiodynamic polarization curves of an LC steel and an ULC Ti‐interstitial free (IF) steel evidencing the effects of carbon content and pearlite fraction on the electrochemical corrosion behaviour. Corrosion tests were carried out in a 0.5 M NaCl solution at 25 °C with a pH range between 6.5 and 6.8. It was found that the IF steel sample presents an electrochemical corrosion resistance, which is slightly higher than that of the LC steel sample.     

氯离子含量对黄壤土中碳钢腐蚀行为的影响

利用极化曲线技术、电化学阻抗测试技术等方法,研究了氯离子含量对黄壤土中碳钢腐蚀行为的影响。实验结果表明,氯离子对黄壤土中碳钢腐蚀影响显著。碳钢的腐蚀速率随土壤中氯离子含量的增加而增加,当氯离子的质量百分含量增加到0.90%时,腐蚀速率达到最大,然后腐蚀速率随着氯离子含量增加有所减小。碳钢在低氯含量土壤中阻抗谱表现为单容抗弧,在高氯含量土壤中为双容抗弧。     

Effect of humidity and chloride content on the corrosion of steel embedded in LWA concrete

Measurements have been made with mortar specimens with light aggregates (LWA) and the cements Norcem HS65 and MP30, corresponding to CEM I and CEM II. The w/b ratio was 0.30 and 0.40 and in one mix prewetted LWA was used. The silica fume addition was 8%. The specimens have two sets of electrodes consisting of a 10 mm reinforcing steel and a 10 mm rod of stainless steel. In the start of the experiment the chloride penetration was accelerated by applying a voltage between a negatively charged steel plate within the salt solution and a positively charged net of stainless steel embedded in the concrete above the reinforcing steels. This caused some problems and the set-up was changed to using a Plexiglas brim and a solution of calcium hydroxide and sodium chloride was applied. In the solution, a titanium net was placed and a positive voltage of 12 V was applied between the embedded steels and the net with the titanium net as the positive pole. Measuring galvanic currents, electrochemical potential and polarisation resistances have presented a good picture of the corrosion activity of the embedded steels. There is a distinct effect of the humidity upon the corrosion activity registered by the electrochemical measurements. There is a good relation between the electrochemical measurements and the observed corrosion attacks at the end of the experiments. The LWA concrete with water saturated aggregates showed more corrosion than the corresponding LWA concrete with dry aggregates. The rates of corrosion measured both as a galvanic current and as a function of the polarisation resistance showed that the concrete with watered aggregate concrete had a corrosion rate about twice as high as the corresponding LWA concrete with dry aggregates. There are marked differences in the chloride penetration for the different cements. Effects have been observed on the chloride content of the different concretes. Lower w/b ratio, MP30 cement compared to HS65 and no prewatering of the LWA gave less chloride penetration.     

Effects of microplasma arc AISI 316L welds on the corrosion behaviour of pipelines in LiBr cooling systems

The effect of microplasma arc welding (MPAW) on the electrochemical and corrosion behaviour of AISI 316L stainless steel tubes has been studied. Scanning electrochemical measurements were performed in sodium chloride to evaluate the difference in the electrochemical activity of base (non-welded) and welded samples. Oxygen reduction rates increase in AISI 316L due to the heat treatment effect induced by welding, indicating a higher electrochemical activity in the welded samples. Additionally, the use of MPA weldments in lithium bromide (LiBr) absorption machines was also analysed at typical operating temperatures and Reynolds numbers. The welding process increases corrosion rates, hinders passivation and increases the susceptibility to pitting attack in LiBr. However, zero-resistance ammeter and localization index measurements show that the galvanic pair generated between the base and welded alloys is weak, both electrodes being in their passive state. Temperature greatly affects the corrosion process.     

Electrochemical behavior of thermally sprayed stainless steel coatings in 3.4% NaCl solution

Four types of stainless steel coatings prepared by a high velocity oxy-fuel spraying system (HVOF) were studied. Differences among coated steels were related to the spraying parameters, which influenced the behavior of the samples against the corrosion. The electrochemical behavior of the stainless steel coatings was strongly influenced by porosity, the presence of micro- and macro-cracks, and also of un-melted particles. Once the electrolyte reached the steel substrate via these defects, the galvanic pair formed between the coating and substrate-accelerated corrosion, leading to the depletion of the coating.     

铣削加工参数对304奥氏体不锈钢耐蚀性的影响

利用电化学动电位极化法测试了不同铣削加工参数下304奥氏体不锈钢的腐蚀行为。结果表明:铣削加工后材料的耐蚀性高于原始材料的。耐点蚀能力随着铣削加工进给率和切削速率的上升而下降,不同加工参数之间材料的点蚀电位差高达138mV,表明铣削加工参数对于奥氏体不锈钢的耐蚀性有着强烈的影响。     

不锈钢包钢在红壤中的电偶腐蚀行为

通过失重法、电化学方法研究了不锈钢包钢在红壤中的电偶腐蚀行为,采用SEM、XRD观察分析试样的表面形貌及腐蚀产物。结果表明:不锈钢-碳钢电偶对的形成加速了阳极金属材料的腐蚀,随着电偶对阴阳极面积比的增加,电偶电流逐渐增大;不锈钢在浸泡45d后基本没有发生腐蚀,而碳钢则发生了极严重的全面腐蚀,腐蚀产物主要为铁的氧化物。     

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.     

Effects of copper on the corrosion properties of low-alloy steel in an acid-chloride environment

The influence of Cu addition on the corrosion resistance of low-alloy steel in an acid-chloride solution was investigated by electrochemical methods, such as potentiodynamic polarization tests and an electrochemical impedance spectroscopy (EIS). The XPS analysis of the corroded surfaces indicated the formation of protective Cu₂O and Cu(OH)₂ layers on the surface. The formation of Cu products on the surface reduced the uniform corrosion rate of the steel, but promoted localized corrosion due to the galvanic interaction between the covered areas of copper oxide/hydroxide and the uncovered areas on the surface of steel.     

核电汽轮机转子堆焊焊接接头的电偶腐蚀行为及有限元仿真

采用宏观电化学试验和浸泡试验研究25Cr2Ni2MoV汽轮机转子堆焊焊接接头在80 ℃,3.5% Cl?环境下的电偶腐蚀行为. 电化学试验结果表明,焊缝为腐蚀薄弱区,腐蚀电位从高到低依次为热影响区、母材、焊缝. 浸泡试验结果表明,随着母材面积的增大,焊缝平均腐蚀厚度逐渐加深. 进一步利用宏观电化学测试所获的电化学参量建立焊接接头电偶腐蚀有限元模型对比浸泡试验结果. 结果表明,有限元仿真结果能有效模拟堆焊焊接接头的电偶腐蚀行为,为实际生产提供电偶腐蚀速率预测.     

镀镍碳钢在高温无氧水中的腐蚀电化学行为

利用线性极化法、极化曲线法和交流阻抗技术研究了化学镀非晶态Ni-P和电镀纳米Ni处理的碳钢在高温无氧水中的腐蚀电化学行为.结果表明,功能镀镍薄膜/碳钢复合材料在高温无氧水中的腐蚀是在电偶腐蚀条件下因氢去极化引起的电化学腐蚀,腐蚀的特征是点蚀,腐蚀的程度取决于镀层的均匀程度和镀层自身的耐蚀能力.     

Corrosion behaviour of corrugated lean duplex stainless steels in simulated concrete pore solutions

This work studies the corrosion behaviour of two corrugated lean duplex stainless steels (SAF 2001 and 2304 grades) in eight alkaline solutions (carbonated and non-carbonated, saturated Ca(OH)₂ solutions with different chloride contents). 2001 stainless steel is a new grade in market because of its composition. 2304 is a grade previously studied under different conditions. However, its use as reinforcement in concrete is new. Studies are carried out by polarization curves following scanning electronic microscopy (SEM) and optical observations. Results are compared to those of carbon steel and austenitic AISI 304 and duplex SAF 2205 under similar conditions. After corrosion tests in alkaline media with chloride, ferrite tends to corrode selectively in 2304 duplex, while austenite corrodes selectively in 2001 under the same conditions. The influence of the duplex microstructure on attack development and morphology is analyzed. The electrochemical parameters obtained from the polarization curves suggest 2001 could replace 304 keeping the structure its corrosion performance (and with clear economical advantages). 2304 shows better corrosion behaviour than the more expensive 304, but somewhat lower than the excellent behaviour shown by 2205.