包钢X70管线钢大气腐蚀行为研究

包钢生产的X70管线钢在露天环境中暴露放置3年后,钢管表面腐蚀并不严重,具有类似耐候钢的腐蚀形貌特征,而国内某钢厂生产的X70管线钢在相同环境下放置相同时间后,表面腐蚀较为严重,文章通过采用周期腐蚀试验对包钢生产的X70管线钢与国内某钢厂生产的X70管线钢进行对比分析,研究包钢X70管线钢耐大气腐蚀行为规律。     

Effect of the Deformation Twin Density on the Corrosion Behavior in TWIP Steel

Based on its excellent tensile strength-ductility property combination,twinning-induced plasticity (TWIP) steel shows great potential in applications for structural components in automobile industry.The aim of this research is to investigate the corrosion resistance properties and corrosion mechanism under room temperature in TWIP steel.The influence of the deformation twin density on corrosion property was primarily considered by salt spray test.The specimens used in the investigation are as-annealed and as-deformed respectively.The microstructure and corrosion resistance property were characterized by scanning electron microscope (SEM),optical microscope (OM) and so on.There are some annealing twins distributed randomly in austenitic grains in the as-annealed specimen.After the specimen was subjected to tensile experiment,the density of the deformation twins increased sharply,which are different from the annealing twins in size and morphology.It was found that the corrosion potential of the as-annealed is lower than that of the as-deformed and the corrosion current density behaves contrarily.After immersed in 5% NaCl solution salt spray for 48h,the as-deformed showed a bit better than the as-annealed in corrosion resistance.With the time prolonged,the gap between the two specimens in corrosion resistance increased rapidly.The corrosion morphologies varied in color and shape.Further investigation,carried out by SEM and EDS,indicated that as-annealed and the as-deformed followed pitting corrosion and uniform corrosion mechanism respectively.The reason for the difference in corrosion mechanism is possibly the presence of the deformation twins.The deformation twins formed during the tensile test refine grains by way of segmentation.The twin boundaries largely belong to the coincidence site lattice (CSL),which is on lower energy state.It suggests that the twins not only play a role in strengthening,but also improve effectively the corrosion resistance in TWIP steel.     

Effect of Cr on Characteristic of Rust Layer Formed on Low Alloy Steel in Flow-accelerated Corrosion Environment

The flow-accelerated corrosion experiments were carried out to research the effect of Cr on the rust layers formed on the carbon steel and Cr-containing steel,as well as the structure of rust layer of the two experimental steels.The influence of Cr on the flow-accelerated corrosion resistance and the corrosion morphology of inner rust layer formed on the Cr-containing steel were studied by the methods of polarization curves,scanning electron microscope,transmission electron microscope,and X-ray photoelectron spectroscope.The distribution of Cr and its form of existence in the inner rust layer were analyzed.The results show that corroded mass loss of Cr-containing steel is lower than that of carbon steel and its inner rust layer is compact.Cr exists in the form of Fe2CrO4 and is enriched in the inner rust layer.This concentration could make the inner rust layer exhibit the tendency of amorphous.This phenomenon is related to fine Fe2CrO4.The inner rust layer becomes more compact because of the formation of fine Fe2CrO4,and the protectiveness of inner rust layer could be improved remarkably.     

Effect of Sulfate Reduced Bacterium on Corrosion Behavior of 10CrMoAl Steel

 The effects of sulfate reduced bacterium (SRB) on the corrosion behavior of 10CrMoAl steel in seawater were studied by chemical immersion, potentiodynamic polarization, electrochemical impedance spectroscopy measurement, and scanning electron microscope techniques. The results show that the content of element sulfur in the corrosion product of 10CrMoAl steel in seawater with SRB is up to 923%, which is higher than that of the same in sterile seawater. X ray diffraction demonstrates that the main corrosion product is FeS. SRB increases the corrosion rate by anodic depolarization of the metabolized sulfide product. SEM observation indicates that the corrosion product is not distributed continuously; in addition, bacilliform sulfate reduced bacterium accumulates on the local surface of 10CrMoAl steel. Hence, SRB enhances sensitivity to the localized corrosion of 10CrMoAl steel in seawater.     

Q355耐候钢加速腐蚀锈层演变规律研究

利用加速腐蚀试验,对Q345低合金钢和Q355耐候钢不同时间腐蚀后试样的锈层形貌及腐蚀产物进行对比分析,结果表明:两种试验钢的锈层均主要由α-Fe OOH、γ-Fe OOH和Fe2O3组成,随着腐蚀时间延长,α-Fe OOH、γ-Fe OOH含量逐渐增加,Fe2O3含量逐渐降低,锈层颜色呈现黑色→红色→黄棕色的变化规律。与低合金钢相比,耐候钢锈层中α-Fe OOH含量在不同时间腐蚀后均比低合金试验钢高,并较早由不连续块/片状逐渐长大发展成连续/致密的针状或片状物,孔洞少且较致密平整,附着力强,不易脱落。耐候钢的腐蚀率明显低于低合金钢,且在试验涉及的腐蚀时间内变化不大。     

Steel Microstructure Effect on Mechanical Properties and Corrosion Behavior of High Strength Low Carbon Steel

Different thermomechanical treatments were applied to a high strength low carbon steel with a novel chemical composition. As a result, three different microstructures were produced with dissimilar mechanical and corrosion properties. Subsequently, a tempering heat treatment was applied to redistribute the phases in the steel. Microstructure A with 56 pct martensite and 32 pct bainite presented high strength but medium ductility; microstructure C with 95 pct ferrite and 3 pct martensite/austenite resulted in low strength and high ductility, and finally microstructure B with 98 pct bainite and 2 pct martensite/austenite resulted in high strength and ductility. Alternatively the corrosion behavior obtained by polarization curves was characterized in 0.1 M H₂SO₄, 3 M H₂SO₄, 3.5 wt pct NaCl, and NS4 solutions resulting in similar magnitudes, while the corrosion behavior acquired by electrochemical impedance spectroscopy had slightly differences in 3 M H₂SO₄.     

Electrochemical Impedance Spectroscopy and Corrosion Behavior of Co/CeO2 Nanocomposite Coatings in Simulating Body Fluid Solution

A series of Co/CeO₂ (25 nm) nanocomposite coating materials by electrodeposition were successfully prepared containing different cerium oxide composition in the cobalt-plating bath. Stainless steel (304L) was used as support material for nanocomposite coatings. The nano-CeO₂ is uniformly incorporated into cobalt matrix, and the effect on surface morphologies was identified by scanning electron microscopy with energy-dispersive X-ray analysis. Codeposition of nano-CeO₂ particles with cobalt disturbs the regular surface morphology of the cobalt coatings. It should be noted that the as-prepared Co/CeO₂ nanocomposite coatings were found to be much superior in corrosion resistance over those of pure cobalt coatings materials based on a series of electrochemical impedance spectroscopy measurements in simulating body fluid solution. With increase in the nano-CeO₂ particles concentration in the cobalt electrolyte, it is observed that the corrosion resistance of Co/CeO₂ increases. Co/CeO₂ nanocomposite coatings have higher polarization resistance as compared with pure cobalt layers in simulating body fluid solution.     

Effect of Micro-Area pH Value on Formation of Different Rust Phases of Weathering Steel in Initial Corrosion Period

The formation of protective rust layer of atmospheric corrosion resistance was discussed for weathering steel.The rust layers of experimental steels were made by using an accelerating industrial atmospheric corrosion test of dry-wet cyclic immersion.Furthermore XRD were used to measure and analyze the rust layers.The initial corrosion processes below thin water film were observed and the changes of micro-area pH value were measured.The results are as follows:The corrosion processes of P-RE weathering steel are obviously different from those of carbon steel.The surface of P-RE weathering steel rapidly forms α-FeOOH and the micro-area pH value is above 5.4 during the initial corrosion period.While the component of the rust layer for the carbon steel is mainly Fe3O4 and the micro-area pH value is below 3.8.     

Study of the Effect of Mold Corner Shape on the Initial Solidification Behavior of Molten Steel Using Mold Simulator

The chamfered mold with a typical corner shape (angle between the chamfered face and hot face is 45 deg) was applied to the mold simulator study in this paper, and the results were compared with the previous results from a well-developed right-angle mold simulator system. The results suggested that the designed chamfered structure would increase the thermal resistance and weaken the two-dimensional heat transfer around the mold corner, causing the homogeneity of the mold surface temperatures and heat fluxes. In addition, the chamfered structure can decrease the fluctuation of the steel level and the liquid slag flow around the meniscus at mold corner. The cooling intensities at different longitudinal sections of shell are close to each other due to the similar time-average solidification factors, which are 2.392 mm/s^1/2 (section A-A: chamfered center), 2.372 mm/s^1/2 (section B-B: 135 deg corner), and 2.380 mm/s^1/2 (section D-D: face), respectively. For the same oscillation mark (OM), the heights of OM roots at different positions (profile L1 (face), profile L2 (135 deg corner), and profile L3 (chamfered center)) are very close to each other. The average value of height difference (H_D) between two OMs roots for L1 and L2 is 0.22 mm, and for L2 and L3 is 0.38 mm. Finally, with the help of metallographic examination, the shapes of different hooks were also discussed.     

NSB耐蚀钢在NaCl溶液干湿交替作用下的电化学腐蚀行为

采用电化学极化曲线和阻抗谱测试方法,研究了马钢所生产NSB耐蚀船板钢在不同浓度Na Cl溶液干湿交替作用下的电化学腐蚀特征。结果表明:NSB耐蚀钢干湿交替循环试样在3.5%Na Cl溶液中的腐蚀电流密度最大,干湿交替循环在钢基体表面形成内外双锈层。红外光谱锈层相组成分析表明:干湿交替循环试样的腐蚀锈层中都含有Fe3O4和γ-Fe OOH,较高浓度的Na Cl溶液能够抑制α-Fe OOH的生成而促进β-Fe OOH的形成。     

Effects of Corrosion of Steel Reinforcement on RC Columns Wrapped with FRP Sheets

This study investigated the effectiveness of carbon fiber-reinforced polymer (CFRP) sheets in protecting reinforced concrete (RC) columns from corrosion of steel reinforcement. Thirty small-scale RC columns and four midscale RC columns were used in this study. The small-scale columns were used for a comprehensive parametric study, whereas the midscale columns were used to evaluate design guidelines proposed based on the results of the small-scale column tests. The test columns were conditioned under an accelerated corrosion process and then tested under uniaxial compression up to failure. The test results showed that although CFRP sheet wrapping decreased the corrosion rate, the corrosion of steel reinforcement could continue to occur, eventually showing a decrease in ultimate axial compression capacity. Design guidelines were proposed based on the small-scale RC column tests and evaluated through a comparison with the test results of midscale RC columns. The proposed design guidelines introduced a concept of effective area to account for the corrosion damage, such as internal cracking and cross-sectional loss of steel reinforcement.     

JT245经济型耐候钢锈层的电化学研究

从电化学的角度出发,采用自然腐蚀电位测定、线性极化、阳极极化、交流阻抗等试验方法对经济型耐大气腐蚀钢JT245的锈层和裸钢的耐大气腐蚀性能进行了实验研究,并与Q235B及Corten A钢进行了对比.试验表明：JT245钢在大气腐蚀过程中生成的锈层,使电化学阳极过程受到显著的阻滞.从热力学上看,JT245钢的自然腐蚀电位正移;从动力学上看,锈层表面趋于钝化,阳极电流降低两个数量级以上.     

Corrosion of Steel Reinforcement in Carbon Fiber-Reinforced Polymer Wrapped Concrete Cylinders

The rehabilitation, repair, and strengthening of concrete structures has increased worldwide with a growing number of systems employing externally applied fiber-reinforced polymer (FRP) composites. However, the service life and effectiveness of FRP repair and strengthening techniques when applied to concrete in corrosive marine environments is still not well understood. This paper presents the results of an experimental study on the corrosion performance of embedded steel reinforcement in cylindrical reinforced concrete specimens with 13 different surface treatment options. Samples were subjected to an impressed current and a high salinity solution. Test variables included the type of epoxy, wrap fiber orientation, and the number of wrap layers. Samples were evaluated for corrosion activity by monitoring corrosion potentials and impressed current flow levels, and by examining reinforcement mass loss and concrete chloride content among samples. Test results indicated that FRP wrapped specimens had prolonged test life, decreased reinforcement mass loss, and reduced concrete chloride content. The performance of wrapped specimens was superior to that of either control samples or those coated only with epoxy. Epoxy type had a significant effect on the performance of samples regarding their resistance to corrosion. It was concluded that carbon FRP wraps were able to confine concrete, slowing deterioration from cracking and spalling and inhibiting the passage of salt water.     

铜对碳钢耐大气腐蚀性能的影响

通过实验室干湿周浸加速腐蚀试验，研究了模拟工业大气环境下，合金元素Cu对碳钢耐腐蚀性能的影响。利用XRD测定腐蚀产物的相组成，通过SEM观察腐蚀试样表面及截面形貌。结合失重法及电化学方法对Cu提高碳钢耐腐蚀性能的机理进行研究分析。结果表明：Cu对碳钢耐腐蚀性能具有明显的促进作用，添加025％的Cu使碳钢的腐蚀速率明显下降，腐蚀抗力平均提高65％以上，含铜钢的腐蚀产物主要由稳定的aαFeOOH及少量γ-FeOOH构成，锈层较碳钢锈层更加致密，腐蚀电流较小。     

Effect of Heat Input on Microstructure and Corrosion Behavior of Duplex Stainless Steel Shielded Metal Arc Welds

In the present work, UNS S32750 super duplex stainless steel sheets were welded by shielded metal arc welding process with E2595 electrode using two different heat inputs, 0.54 and 1.10 kJ/mm. Microstructural investigations (optical and scanning electron microscopy) showed very small differences in the heat affected zone for both the heat inputs. The weld metals showed presence of three different morphologies of austenite—Widmanstatten, intra-granular and grain boundary austenite along with ferrite. Ferrite content in the weld region was also nearly same and did not change significantly with the increase in heat input. Both the weldments showed similar mechanical properties (ultimate tensile strength, impact strength and hardness) and failed in a ductile manner. Electrochemical studies in 3.5% NaCl solution showed the degree of sensitization to less than 1% and nearly same pitting potential for both heat inputs. Since the effect of heat input on the weld behavior was negligible, low heat input may be preffered for welding UNS S32750 super duplex stainless steel.     

Effect of Ca^2＋ and Mg^2＋ on CO2 Corrosion Behavior of Tube Steel

Corrosionfailurecasesobservedinoil fieldaremainlycausedbylocalcorrosion ,whicharealwaysfoundinthedefectareasofcorrosionproductlayer .Thecompositionandmicrostructureofcorrosionprod uctlayeraffectthecorrosionrateandcorrosionmor phologystrongly[1- 3] .Ca2 a…     

Effect of Thermomechanical Processing and Crystallographic Orientation on the Corrosion Behavior of API 5L X70 Pipeline Steel

Metallurgical and Materials Transactions A - This work presents the electrochemical response of X70 pipeline steel substrates thermomechanically processed at different conditions. The WE sample was...     

经济型耐大气腐蚀钢JT245的腐蚀性能

采用电化学方法、电子探针对经济型耐大气腐蚀钢JT245、Q235B钢和Corten A钢在北京、青岛、沈阳经1年大气暴露的试样进行了分析,研究了它们的耐大气腐蚀性能和变化规律.     

镀锌卷白锈浅析

在通过分析白锈产生原因及对从镀锌钢卷下线到客户各流通环节引起白锈异议的情况分析,指出了白锈发生的源头,通过控制影响因素,降低白锈异议。