Corrosion of Q235 steel affected by Pseudodesulfovibrio cashew differed with electron acceptors

Sulfate and nitrate reducing bacteria are important culprits for microbiologically influenced corrosion(MIC)using sulfate and nitrate as electron acceptors,respectively.Sulfate and nitrate hold different standard electrode potentials,which may lead to differences in corrosion,but their effects on corrosion by the same bacteria have not been reported.The corrosion of Q235 steel affected by Pseudodesulfovibrio cashew(P.cashew)in the sulfate and nitrate media under carbon starvation was studied.It was found that sulfate and nitrate did not lead to differences in corrosion under abiotic conditions.However,P.cashew promoted corrosion in both cases,and the consumption of H_(2)was the main mechanism for MIC.In addition,corrosion was more severe in the sulfate media.The higher corrosivity of P.cashew with sulfate as the electron acceptor is closely related to the higher number of sessile cells in the biofilm,higher bacterial motility,more hydrogen production pathways,and the increased gene expression of enzymes related to energy synthesis.

Q235钢表面Ni-Cr电镀层的组织及性能

为提高Q235钢的表面防护性能,对其进行表面电镀Ni-Cr处理,并采用正交试验对电镀Ni-Cr工艺进行优化。采用X射线衍射仪(XRD)、扫描电镜(SEM)和激光共聚焦显微镜(OM)分别对镀层进行物相表征和形貌观察,利用显微硬度计、磨粒磨损机和电化学工作站对镀层硬度和耐蚀性进行研究。结果表明:以镀层沉积速率为指标,正交试验所得电镀Ni-Cr优化工艺为柠檬酸钠含量30 g/L,镀液pH值3.0,电流密度20 A/dm^2,电镀温度35℃,镀层沉积速率可达40.17μm/h;Ni-Cr镀层相结构由γ-Ni和Cr_(1.22)Ni_(2.88)组成;镀层表面平整,表面形貌为密集球形颗粒;与基体相比,正交试验所得Ni-Cr镀层硬度提高了81.62~649.08 HV_(2N),磨损率减少了9.14~29.99mg/cm^2,自腐蚀电位提高了2.05~121.28 mV。

锻压工艺参数对Q235-Cr钢建筑脚手架扣件性能的影响

采用不同的工艺参数对Q235-Cr钢建筑脚手架扣件进行了锻造,并对试样进行了耐腐蚀性能和冲击性能的测试与分析。结果表明:在试验条件下,随始锻温度从1200℃升高至1300℃,终锻温度从685℃升高至745℃或锻压速度从20 mm/min增大至50 mm/min,扣件的耐腐蚀性能和冲击性能均先提高后下降。扣件的最佳锻压工艺参数为:始锻温度1275℃、终锻温度715℃和锻压速度40 mm/min。

Corrosion behavior and electrochemical property of Q235A steel in treated water containing halide ions(F^-, Cl^-) from nonferrous industry

The corrosion behaviors and electrochemical properties of Q235 A steel in the treated water containing corrosive halide anions(F-, Cl-) have been investigated with corrosion tests of static coupon and dynamic coupon testing, electrochemical measurement of open-circuit potential and linear sweep voltammetry. The results reveal that the existence of F-and Cl-ions in the simulated treated water accelerate the corrosion rate of Q235 A steel. The corrosion rate reaches maximum with F-concentration of 50 mg/L, Cl-concentration of 200 mg/L, respectively. However, Q235 A steel would passivate when an applied potential is added to the system. Meanwhile, the initiating passive potential becomes positive with F-, Cl-concentration increasing. There is a little influence of F-, Cl-concentration on the initiating passivation current density. Therefore, it is necessary to control F-, Cl-concentration in the treated water when it is recycled by the pipelines made of Q235 A steel.

Effect of Surface Nanocrystallization on Cr-Rare Earth-Boriding for Steel Q235 at Low-Temperature

A nanostructured layer was fabricated on the surface of steel Q235 by using fast multiple rotation rolling( FMRR). The Cr-Rare earth-boriding process was carried out followed at different temperatures.Experimental results showed that the thickness of the boride layer was significantly increased by surface nanocrystallization. The morphology of the boride layer was saw-toothed. An uniform,continuous and dense boride layer was obtained and adhered well to the substrate. The penetrating speed of FMRR specimens was enhanced by 1.9,1.7 and 1.5 times when the Cr-Rare earth-boriding temperature was 843,873 and 923 K.Severe plastic deformation,which grain size was approximately 100 nm,was observed on steel Q235 surface.Mechanism of Cr-Rare earth-boriding was also studied.

Prevention of Q235 Steel Corrosion using Waterborne Rust Inhibitor

Sorbitol,triethanolamine,sodium benzoate,boric acid,and sodium carbonate were mixed to prepare a waterborne rust inhibitor.A temperature and humidity accelerated corrosion test was applied to investigate the corrosion behaviour of waterborne rust inhibitor coated Q235 steel and original Q235 steel,which was carried out in a temperature and humidity test chamber(WSHW-1000)at a temperature of 80℃and humidity of 95%.Compared with the original Q235,waterborne rust inhibitor coated Q235 has better resistance to corrosion in hot and humid ambient conditions.Electrochemical impedance spectroscopy and potentiodynamic polarization were measured with a three-electrode cell in 3.5%NaCl aqueous solution on a CHI760E potentiostat/galvanostat.Molecular dynamics was simulated to verify the synergistic corrosion inhibitory mechanism of sodium carbonate and triethanolamine.The test shows that the prepared waterborne rust inhibitor can reduce the tendency of Q235 to corrosion and can also effectively reduce the corrosion rate.

Corrosion-fatigue evaluation in Q235A steel using nonlinear Rayleigh surface waves

This paper presents a non-destrcutive evaluation method for the evolution of corrosion fatigue of Q235A steel. Specimen surface degradation due to corrosion fatigue from the combined interaction of corrosion and cyclic loading leads to harmonic generation during Rayleigh wave propagation along the specimen surface,which allows for an early prediction of material fatigue life. The relative nonlinearity parameter β as an evaluation parameter,which is denoted as a ratio of fundamental and second-order harmonic amplitudes,is measured by using an experimental platform based on a pair of wedge transducers to launch and receive Rayleigh wave signal. Subjected to an immersion corrosion method with 10% NaCl solution and a 20 Hz cyclic loading,a corrosion-fatigue specimen was made,and its relative nonlinearity parameter was measured every 10 5 cycles until to 7 ×10^5 cycles. A measured curve of relative nonlinearity parameter versus fatigue load cycles,which is produced by surface degradation of specimen corrosion fatigue,showed an initial steady trend followed by a rapid increase. Experimental results demonstrate that corrosion fatigue results in the sudden destruction of a Q235A steel specimen and nonlinear Rayleigh surface waves measurement technique can be used to quantitatively characterize fatigue life of Q235A steel.

Q235钢表面电镀镍及其性能的研究

在Q 235钢表面电镀镍,以提高低碳钢表面的耐蚀性和可焊接性。对碱洗、酸洗、活化等前处理工艺进行了研究,着重研究了直流电镀和脉冲电镀的工艺参数和镀镍层的性能。结果表明:直流镀镍层和脉冲镀镍层都较为均匀、致密、无明显缺陷,且脉冲镀镍层比直流镀镍层结构更加紧密;加搅拌后所得镀层的实验结果明显优于不加搅拌时所得镀层的;脉冲镀镍层的自腐蚀电位明显高于直流镀镍层的,且加搅拌后,自腐蚀电位进一步提高。

Q235钢脉冲加弧辉光渗镀铬镍后的电化学性能

为了改善Q235钢的抗腐蚀性能,采用脉冲加弧辉光离子镀技术对其渗镀铬镍。利用X射线衍射、扫描电镜(SEM)对Q235钢表面铬镍合金渗镀层进行了分析,同时探讨了其电化学性能。结果表明:Q235钢渗镀铬镍后表面形成了Cr0.19Fe0.70Ni0.11合金层,明显提高了其抗腐蚀性能。

Q235碳钢表面镍铬合金化层的耐海水好氧菌腐蚀性能

目的揭示弧辉等离子体镍铬共渗处理对Q235碳钢表面成分、结构和耐海水好氧菌腐蚀性能的影响。方法采用弧辉等离子体渗镀技术在Q235碳钢表面制备镍铬合金化层。利用X射线衍射仪(XRD)和扫描电子显微镜(SEM)对镍铬合金化层的相组成、表面形貌和截面元素分布进行分析。利用电化学测试技术,测试并分析镍铬合金化层在海水好氧菌中的腐蚀电化学行为。结果Q235碳钢经弧辉等离子体镍铬共渗后,表面形成了一层厚度约为50μm的镍铬合金化层,合金化层的物相为Ni_(2.9)Cr_(0.7)Fe_(0.36)固溶体。在好氧菌中浸泡时,Q235碳钢表面形成了生物腐蚀膜,腐蚀膜的存在使Q235碳钢的腐蚀电位负移,局部耐蚀性降低。与Q235碳钢相比,镍铬合金化层的表面能降低,表面接触角达到111°。镍铬合金化层在好氧菌中浸泡11 d后,仅在很少的局部位置观察到细菌附着,未观察到明显的腐蚀膜。结论Q235碳钢在好氧菌中浸泡时腐蚀严重,浸泡5 d后就在其表面形成了一层由腐蚀产物、培养基和细菌形成的腐蚀产物膜,腐蚀产物对生物膜的形成有一定的促进作用。镍铬合金化层降低了Q235碳钢表面的表面能,阻碍生物膜底膜的形成,同时形成的钝化层对介质有一定的阻隔,显著提升了耐好氧菌腐蚀的性能。

Numerical simulation of stress distribution in Al_2O_3-TiC/Q235 diffusion bonded joints

The distributions of the axial stress and shear stress in Al2O3-TiC/Q235 diffusion bonded joints were studied using finite element method （FEM）. The effect of interlayer thickness on the axial stress and shear stress was also investigated. The results indicate that the gradients of the axial stress and shear stress are great near the joint edge. The maximal shear stress produces at the interface of the Al2O3-TIC and Ti interlayer. With the increase of Cu interlayer thickness, the magnitudes of the axial stress and shear stress first decrease and then increase. The distribution of the axial stress changes greatly with a little change in the shear stress. The shear fracture initiates at the interface of the Al2O3-TiC/ Ti interlayer with high shear stress and then propagates to the Al2O3-TIC side, which is consistent with the stress FEM calculating results.

双辉等离子表面Ni-Cr合金渗层的组织及耐蚀性能研究

采用双层辉光等离子表面冶金技术在Q235钢表面制备Ni-Cr合金渗层,对合金渗层的组织特征、成分和耐蚀性能进行了研究。结果表明:Ni-Cr合金渗层与基体呈现良好的冶金结合状态;渗层中Ni,Cr元素含量由表及里逐渐减少,厚度约为30μm,渗层主要物相为Ni2.9Cr0.7Fe0.36。电化学极化试验表明经Ni-Cr共渗处理后试样的耐蚀性明显优于基材,且Ni-Cr合金渗层的保护效率高达99.7468%,而孔隙率仅有0.2%。

双辉等离子表面冶金的Ni-Cr合金层组织结构及耐蚀性能研究

为了改善Q235碳钢表面耐蚀性能,采用双辉等离子表面冶金技术在其表面制备Ni-Cr合金层。研究了极间距对合金层组织结构的影响规律,并对合金层的组织成分和耐蚀性能进行检测分析。结果表明:随着极间距增大,Ni-Cr合金层厚度呈现先增加后减小的趋势;Ni-Cr合金层组织均匀致密,与基体呈冶金结合状态,合金层厚度约为95μm,主要物相为Ni2.9Cr0.7Fe0.36和少量Ni3Fe。电化学极化曲线试验结果显示Ni-Cr合金层的自腐蚀电位和极化电阻较基材Q235高,而自腐蚀电流密度较低,即Ni-Cr合金层更难以发生电化学腐蚀反应且腐蚀速率更低。表明Q235钢经Ni-Cr共渗处理后,其耐蚀性得到明显改善。

原位复合(Nb-Cr-Ti)C堆焊金属的组织与性能

工业机械设备表层磨损失效非常普遍,堆焊是其最有效的保护方法之一。采用自制焊条,通过对堆焊合金的组织结构设计和成分调整,自行设计了Nb-Cr-Ti系堆焊金属,并堆焊出了耐磨抗裂的合金层。采用光学显微镜、扫描电镜、能谱分析仪器以及磨损试验机等,分析了堆焊层组织结构和性能,探讨了各合金元素在堆焊层中的作用。结果表明:堆焊层组织为混合型马氏体和少量残余奥氏体+弥散分布的复合(Nb-Cr-Ti)C颗粒,低碳马氏体和高碳马氏体数量相当。铌在高温下先析出生成硬质相NbC,碳化物硬质点呈颗粒状弥散分布,使组织细化,也使焊层达到较高的硬度,提高了耐磨性。碳化物的大量弥散析出,使得基相含碳量较低而转变成低碳马氏体,因基相有较高的塑韧性,抗裂性增强。该堆焊层的耐磨性和抗裂性明显优于商用D667焊条。

Microstructures and mechanical properties of metal inert-gas arc welded Mg-steel dissimilar joints

The joining of Mg alloy to steel was realized by metal inert-gas arc welding, and the weld thermal cycle characteristics and Mg-steel joints were investigated. The results show that the temperature distribution in the joints is uneven. Mg alloy welds present a fine equiaxed grain structure. There exists a transition layer consisting mainly of AlFe, AlFe3 and Mg（Fe, Al）2O4 phases at Mg/steel interface, and it is the weakest link in Mg？steel joints. The welding heat input and weld Al content have the significant effect on the joint strength. The joint strength increases with increasing the heat input from 1680 J/cm to 2093 J/cm, due to promoting Mg/steel interface reaction. When weld Al content is increased to 6.20%, the joint strength reaches 192 MPa, 80% of Mg alloy base metal strength. It is favorable to select the suitable welding heat input and weld Al content for improving joint strength.

等离子熔覆Fe-Cr-C合金涂层工艺优化及性能研究

目的采用等离子熔覆技术在Q235钢表面制备Fe-Cr-C合金熔覆层,提高基材表面的硬度和耐磨性。方法通过正交试验确定最佳工艺参数,用SEM、EDS、XRD分析熔覆层的组织结构和物相,用显微硬度计和摩擦磨损试验机测试熔覆层的硬度和耐磨性。结果工作电流和送粉速度对等离子熔覆层的硬度和磨损量的综合影响最为显著,最佳工艺参数为:工作电流110 A,扫描速度110 mm/min,送粉速度6 r/min,搭接率40%,离子气流量1 L/h。熔覆层硬质相为(Cr,Fe)7C3,其余物相为γ-Fe、(Fe,Cr)、(Fe,Ni)、(Fe,C)、(Fe,Ni)23C6、Cr7C3、Ni3Si、Fe3Mo、Fe2Nb。最优参数试样熔覆层的平均显微硬度为545.1HV0.5,比Q235钢基体的硬度高3倍左右。经过5 h摩擦磨损试验后,其总磨损量为0.25 g,比基体磨损量减少约2/3;磨损体积为45.09 mm3,约为基体磨损体积的1/3;磨损率为1.22×10^−4 mm^3/(N·m),约为基体磨损率的1/3;摩擦系数为0.23,约为基体摩擦系数的1/2。结论在Q235钢基体表面采用等离子熔覆技术制备出Fe-Cr-C合金熔覆层,其硬度和耐磨性能得到显著提升。

Microstructure characteristics and mechanical properties of steel stud to Al alloy by CMT welding-brazing process

Cold metal transfer （CMT） welding of nickel-coated Q235 steel studs with 606l Al alloy was carried out using ER4043 as filler metal. The welding process was stable, and appearance of weld formed well without surface defect under the parameters of welding current 121 A, welding voltage 15.4 V and welding speed 6 r/min. The microstructure of fiUer metal was analyzed by means of scanning electron microscopy. The filler metal and 6061 Al alloy were fused to form fusion welding interface, the fusion zone had a good bonding without any micro defect. The steel stud did not melt and brazing interface was formed between the filler metal and steel stud. Two different reaction layers existed in the brazing interface, the Fe2Al5 layer about 10 -12 p^m formed near the steel stud side, and the other layer was mainly composed of FeAl3. Nickel-rich zone was formed in the root toe area of the fillet weld, which was mainly composed of Al3Ni2. The tensile tests showed that the maximum shearing strength of the joints was 129 MPa. The joint was brittle fractured in the intermetallic compound layer where plenty of FeAl3 were distributed continuously.

Experimental investigation on ablation characteristics of coated and uncoated steel under 30/80 μs impulse current

The ablation tests on coated and uncoated Q235 B steel sheets were conducted under 30/80 μs impulse current simulating the lightning first return stroke current, aimed at further understanding the ablation characteristics of steel and investigating the impact of anti-corrosion coating on these characteristics. Ablation characteristics were investigated through the macroscopic morphology and x-ray diffraction patterns on the surface of damaged zones, the microstructure and micro Vickers hardness on the cross-section of damaged zones, and the maximum rear-face temperature of sample sheets. It can be concluded that the ablation areas of uncoated sheet consist of the melted layer and the heat-affect layer. These ablation areas include not only the area ablated directly by the arc root, of which the depth is deeper, but also the area forming due to the splashing of molten steel, of which the depth is shallower and decreases when the area’s distance from the arc attachment point increases. For coated sheet, coating materials have decomposed and evaporated forming an ablation pit on the sheet surface, in which the steel surface is exposed, and zinc filler of coating primer has infused into the exposed surface. The ablation diameter of uncoated sheet relates to the amplitude of the 30/80 μs impulse current in quadratic function, while for coated sheet, the relation is linear. In general, under the 30/80 μs impulse current, the coating can decrease the energy injected from the arc to the steel sheet and reduce the melting and splashing of steel. As a result, the ablation severity of uncoated sheet is severer than that of coated sheet.

Atmospheric Corrosion of Q235 Carbon Steel and Q450 Weathering Steel in Turpan,China

Q235carbon steel and Q450 weathering steel were exposed to the hot and dry environment of Turpan,China for three years.The corrosion rates of both steels were calculated and compared.The morphologies of the rust layer products were observed by optical microscopy and scanning electron microscopy.Analyses of the rust layers were performed by X-ray photoelectron spectroscopy,X-ray powder diffraction,and Raman spectroscopy,and analysis results indicate that the compositions of rust are main iron rich oxide such as FeOOH,Fe_3O_4,and Fe_2O_3.The iron oxide layer content proportion was calculated through a semi-quantitative algorithm.The resistance elements（Cr,Ni,and Cu）enhanced the resistance properties of the Q450 weathering steel matrix.Moreover,the resistance elements increased the proportion of goethite crystals in the corroded rust layer.

Simulated Corrosion Test of Q235 Steel in Diatomite Soil

Through the study of the corrosion behavior of Q235 steel in actual Yingtan soil and two simulated acidic soils with different water contents, the calculation of corrosion mass losses, and the analysis of the corrosion mor- phologies and products by means of scanning electron microscope （SEM） and X-ray diffraction （XRD）, the results demonstrated that the diatomite soil could simulate the corrosion in actual soil veritably. In both actual soil and simu- lated soil with 16.4% water content, the corrosion rates of Q235 steel were approximately 0.1 mm/a, the corrosion morphologies were mainly extension and connection of corrosion spots on sample surface, and the corrosion products were composed of a-FeOOH, γ-FeOOH, Fe3 O4 and Fe2O3. When other media conditions remained unchanged, the corrosion area of Q235 steel was larger in simulated soil with 34.5 % water content, and the corrosion rate reached 0.48 mm/a after 360 h of corrosion, which was nearly 5 times as the value in actual soil. Compared with the corro- sion products in actual soil, the proportion of γ-FeOOH in simulated soil with 34.5 % water content was higher, and the wα-FeOOH/wγ-FeOOH ratio was 1. 4, which was only 1/3 of the value in actual soil.