基于不同保护层厚度下混凝土构件角区锈胀裂缝宽度与钢筋锈蚀率的关系研究

采用人工通电加速锈蚀法来获得6个不同锈蚀结果的锈蚀钢筋混凝土构件,在锈蚀钢筋混凝土试件的三个锈蚀表面划分网格,用裂缝观测仪对裂缝进行观测并记录裂缝的宽度值.将钢筋混凝土试件进行破型处理,获得对应裂缝位置处的钢筋锈蚀率.针对试验获得的保护层为10 mm、20 mm、30 mm下混凝土构件角部锈胀裂缝和锈蚀率的基本数据,通过数据拟合发现不同保护层厚度下锈蚀率和锈胀裂缝宽度存在明显的线性关系.最后,通过统计回归分析,将混凝土构件角部钢筋锈蚀率与裂缝宽度及保护层厚度之间的关系整合为一个回归方程,以方便其在实际工程中的应用.     

保护层厚度对混凝土中钢筋锈蚀的影响

混凝土中的钢筋锈蚀破坏是混凝土结构失效破坏的最主要原因.通过电化学测定,研究了保护层厚度对钢筋锈蚀的影响,研究表明:增大混凝土保护层厚度能有效延缓混凝土中钢筋的锈蚀,延长钢筋开始锈蚀的时间,保护层厚度越大,越能延长钢筋开始锈蚀的时间;进入钢筋开始锈蚀阶段后,保护层比较厚的混凝土中钢筋锈蚀速率增长的较慢;在稳定锈蚀阶段,保护层厚度越大.稳定腐蚀电流密度就越小,保护层厚度和稳定腐蚀电流密度存在一定的函数关系,且数据相关性良好.     

铸钢件表面镀锌层的质量评价

采用覆盖能力和分散能力好的电镀液对铸钢件进行电镀锌.按照国家相关标准对镀层进行质量检测,结果表明该镀层附着力强、光泽度好.通过电子扫描电镜对镀层表面形貌进行分析,结果表明该镀层厚度均匀、致密度好,镀层向基体金属方向呈现锌减少、铁增多的趋势.     

一例钢制壳体外底化学镀镍层锈蚀故障的解决

针对材质为30Cr Mn SiA的某圆筒壳体零件外底面化学镀镍层在湿热试验后出现的锈蚀现象进行了分析。结果表明,镀层的厚度、微观结构和成分均符合要求,但锈蚀部位的镀层孔隙率高达35个/dm~2,可见孔隙率过高是镍镀层锈蚀的主要原因。在施镀前降低基体表面粗糙度,施镀过程中晃动零件,以及进行适当的后处理都能够解决该问题。     

车身钢板及不同电泳膜厚对耐蚀性的影响研究

模拟车身内腔电泳情况,在普通钢板和镀锌钢板两种材料表面电泳4种不同膜厚涂层进行中性盐雾试验。采用扫描电镜等分析手段,探讨锈蚀产生的过程、原因和规律。试验结果表明:电泳涂膜的耐水性、耐盐雾性一般,已发生穿透腐蚀;在涂膜破损的情况下,涂膜厚度增加对阻止破损处锈蚀蔓延的作用不大;在涂膜完好的情况下,涂膜厚度增加,屏蔽作用加强,防锈效果显著;普通钢板试样腐蚀以点蚀形式进行,镀锌钢板试样腐蚀以全面腐蚀形式进行,普通钢板试样更易出现锈穿现象。     

江苏某桥结构混凝土耐久性现场检测与评估研究

对江苏某桥不同的结构部位混凝土外观、力学性能、碳化深度、钢筋保护层厚度、钢筋锈蚀进行现场检测.检测结果表明各个结构部位混凝土存在竖向裂缝.虽然结构混凝土力学性能存在一定波动性,但总体上处于较好和良好状态.结构混凝土的碳化深度较小,碳化深度与钢筋保护层厚度比值均小于1,结构混凝土碳化深度对钢筋锈蚀影响程度为轻微.混凝土钢保护层厚度变化较小,对钢筋耐久性影响不显著.钢筋锈蚀电位检测表明结构混凝土钢筋锈蚀不明显.江苏某桥各个结构部位混凝土使用状态良好.     

铸钢件黑色磷化工艺的研究

通过对黑色磷化各种工艺因素的研究,确定了铸钢件锰系中温黑色耐磨磷化工艺的最佳方案.采用体视显微镜研究了磷化膜表面微观形貌;采用X射线荧光光谱法(XRF)对磷化膜的厚度和成分进行了测定;采用点蚀法对磷化膜的耐蚀性进行了研究.结果表明,磷化膜性能好,磷化液污染小,便于维护和调整;温度适中,节约能源.本文还对磷化液中各成分作用进行了理论分析.     

环境友好型低表面处理环氧涂料的制备

采用润湿性好的环氧树脂,辅以助剂、溶剂、颜填料、固化剂搭配制备出环境友好型低表面处理环氧涂料,以低表面处理环氧涂料在锈层中的渗透性及锈转化测试方法作为评价在锈蚀面性能的依据,再结合锈蚀、潮气、油污染基材表面涂膜的附着力、涂装效果和涂装厚度等数据,结果表明制备的涂料在潮湿、油污、锈蚀基材上有较好的附着力和防腐性能,并且有优异的贮存稳定性和施工性。     

电机叶轮组合镀层斑点原因分析

通过体视显微镜、光学显微镜、扫描电镜及X射线能谱仪对ST13电机叶轮叶片表面进行分析检测,叶片表面为铜/镍/铬组合镀层.分析结果表明:叶片表面的斑点、锈蚀、起皮等缺陷是因氯离子渗入镀层导致的基体点蚀失效,叶片迎风面所受到的高压气流、镀层与钢铁基体的电位差等因素促进了腐蚀反应过程.叶片总的镀层厚度不足5 μm,且作为中间...     

房屋吊顶结构中镀锌轻钢龙骨腐蚀原因分析

采用能谱(EDS)、X射线衍射(XRD)等手段对房屋吊顶结构中镀锌轻钢龙骨的表面锈蚀物进行表征,采用离子色谱(IC)对难燃胶合板的特征离子进行分析,找出轻钢龙骨表面锈蚀的原因,并通过实验进一步验证。结果表明：难燃胶合板中含有吸湿性的阻燃剂(磷酸铵、磷酸二氢铵、磷酸氢二铵中的一种或几种及硫酸铵),其在潮湿的环境中吸收水分后形成了腐蚀性电解质溶液,导致龙骨发生锈蚀。     

表面容忍性涂料的应用和性能评定

介绍了IMO（国际海事组织）颁布的新建和维修钢结构的表面处理等级,以及表面容忍性涂料在锈蚀、污染和旧涂层等非理想表面上的应用。还介绍了几种表面容忍性涂料性能评定的案例。     

金属基有机硅树脂涂层复合材料的导热性能

以锌粉为导热填充剂对环氧有机硅树脂进行改性,考察了改性环氧有机硅树脂涂层干膜中锌粉含量对涂层导热系数的影响,分析了涂层厚度对碳钢基材导热性能的影响. 结果表明,环氧有机硅树脂涂层的导热系数约为0.19 W/(m?K),其耐温能力在200℃以上,可保证涂层在中低温烟气余热回收换热器表层长期工作而不发生任何热反应;添加锌粉可改善环氧改性有机硅涂层的导热性能,涂层干膜锌粉25wt%时,涂层材料导热系数达0.35 W/(m?K),较未添加锌粉时增大了84%. 复合材料的导热系数随涂层厚度增加而下降,无涂层的碳钢导热系数为47.59 W/(m?K),涂层厚度为200 ?m时,导热系数降至34.33 W/(m?K).     

Formation and characteristics of Al−Zn hydrotalcite coatings on galvanized steel

In this study, a process for depositing hydrotalcite (HT) coatings on galvanized steel was developed and the resulting coatings were characterized. Results showed that coatings formed spontaneously on galvanized surfaces upon exposure to ambient temperature alkaline aluminate solutions. Anodic polarization and electrochemical impedance spectroscopy experiments showed clear evidence of surface passivation. Scanning electron microscopy showed the formation of a continuous and conformal surface film comprised on a compact mass of crystallites. X-ray diffraction confirmed that the coating contained an Al−Zn hydrotalcite compound. Coating formation was enhanced by oxidizer and ammonium salt additions. Coatings formed by using best practices were deposited in less than 10 minutes and demonstrated good surface coverage and good organic coating adhesion. HT coatings formed by using best practices showed excellent organic coating adhesion compared to zinc phosphate control coatings. In salt spray testing, the presence of a hydrotalcite conversion coating under an epoxy neat resin was found to delay the onset of red rusting compared to control samples that were epoxy coated, but not conversion coated.     

316不锈钢连铸工艺参数对结晶器内坯壳厚度影响模拟

为研究连铸过程中拉速及过热度对凝固传热的影响,采用商业有限元软件ANSYS,对316不锈钢板坯厚度生长情况进行了模拟. 采用2-D模型,分别计算了拉速为0.4, 0.5, 0.6 m/min及过热度为30, 40, 50℃时坯壳出口温度、坯壳厚度及表面温度的变化,探讨了坯壳生长及厚度变化规律. 结果表明,拉速从0.4~0.6 m/min变化,坯壳出口温度升高83℃、坯壳的出口厚度平均减薄3.2 mm、表面温度随拉速提高而升高;过热度从30~50℃变化,坯壳出口温度升高20℃、表面温度平均升高20℃、坯壳的出口厚度平均减薄1.35 mm.     

推土机及其零部件局部锈蚀的原因及防止措施

推土机涂装后整机和零部件在露天存放、储运过程中表面很快出现局部锈蚀现象,影响了产品整体外观质量。锈蚀部位主要在棱角、拐角、边缘和角接焊缝处。使用高压无气喷枪喷涂导致上述部位虚喷,漆膜厚度没有达到工艺要求。因此,严格规定了棱角、拐角、边缘和角接焊缝处等部位应使用空气喷枪喷涂。     

Computer-aided modeling for predicting layer thickness of a duplex treated ceramic coating on tool steels

Five different tool steels (DIN 1.2080, 1.2210, 1.2344, 1.2510 and 1.3343) have been targeted for a duplex surface treatment consisted of nitriding followed by vanadium thermo-reactive diffusion (TRD). TRD process was performed in molten salt bath at 575, 650 and 725 °C for 1 to 15 h. A duplex ceramic coating of vanadium carbonitride (VCN) with a thickness up to 10.2 μm was formed on tool steel substrates. Characterization of the ceramic coating by means of scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD) indicated that the diffused compact and dense layers mainly consisted of V(C,N) and V₂(C,N) phases. Layer thickness of duplex coating has been modeled by gene expression programming (GEP). Recently, application of GEP as a computer-aided technique has got appreciable attraction especially for modeling and to formulate engineering demands. For GEP approaches, chemical composition of steel substrates along with different bath and processing parameters totally composed of 17 different parameters were considered as inputs to establish mathematical correlations. Finally, the training and testing results in models have shown strong potential for predicting the layer thickness of duplex treated ceramic coating on tool steels.     

CPK法在精密仪器喷涂工艺中的应用

精密仪器表面的涂装,除了要求具备一般涂层的性能外,对涂层厚度的控制十分严格.本文采用品质管理中的CPK法对数码相机镜头部件涂装后的尺寸进行分析,以准确判定该涂装工艺在涂层厚度控制方面的有效性,并根据分析结果优化涂装工艺中的各个参数,从而达到精确控制涂层厚度的目的.     

The long-term effectiveness and failure mechanism of the chemically bonded phosphate ceramic coatings with different thickness

In this study, the chemically bonded phosphate ceramic coatings (CBPCs) with different thickness (100 µm, 200 µm, and 300 µm) are prepared on the mild steel (Q235). Potentiodynamic polarization testing and electrochemical impedance spectroscopy were carried out to study the synthetic effect of coating thickness and etching time (12, 24, 36, and 48 hours) on the corrosion behavior of CBPCs. The surface and cross section microstructure of CBPCs before and after different immersion time in 3.5 wt.% NaCl solution is investigated to better understand the corrosion behavior. Results revealed that the enhanced coating thickness can effectively postpone the corrosive factors infiltration into the substrate and prohibit the corrosion of the mild steel. From the potentiodynamic polarization testing results, the protection efficiency of the coating greatly increases with the increase in etching time. In addition, an increase in 10 000 and 1000 orders of magnitude of impedance value for the CBPCs with 12 hours and 48 hours etching time has been observed, respectively, indicating the CBPCs can effectively protect the mild steel from corrosion damage even with long-term service.     

Poly(vinyl alcohol) coating on copper filament via electrospinning

Nanofiber‐coated conductive filaments, made by electrospinning, can be used extensively in various electronic applications, such as membranes for manufacturing fiber‐shaped batteries and supercapacitors. However, research on the fiber coating mechanism is necessary in order to be able to control the surface morphology and thickness of coated layers. In this study, fiber‐shape coated layers of poly(vinyl alcohol) were electrospun onto conductive filaments. The jet behaviors at various nozzle‐to‐collector distances were observed using charge‐coupled devices and high‐speed cameras. The mechanism of the coating process was determined from visible evidence and an appropriate coating model is suggested. Differences in jet behavior induce differences in the coating location on the filament surface. Consequently, the surface morphology and the thickness uniformity of the coated layer are changed. © 2017 Society of Chemical Industry     

Effects of Ni coating thickness on the microstructure and mechanical properties of resistance-welded WC-Co/B318 steel joints

WC-Co pellets electroplated with different Ni coating thicknesses and B318 steel were resistance welded for carbide-tipped saw blade applications. The effects of the Ni coating thickness on the welding process, interfacial microstructures, and mechanical properties of the joints were investigated. The results showed that the shear force increased before decreasing as the Ni coating thickness increased. When the coating thickness was 40 μm, expulsions began to appear during welding, while a thicker coating resulted in longer expulsion times. Voids and macro cracks were generated at the joints because of the expulsions, which reduced the shear force of the joint. The XRD results of the welding slag and the EDS results of the interface indicate that the microstructures can be divided into five phase categories: light gray (Fe₃W₃C), gray (Co₃W₃C), white (WC), fishbone eutectic structure (Fe₆W₆C), and dark [(γ Fe, Ni) solid solutions]. As a thicker Ni coating hinders reactions between molten Fe and dissolved WC, the joint interface contained more Fe₆W₆C at 20 μm and 30 μm but had more bulk Fe₃W₃C at 40 μm and 50 μm. The upper part of the joint showed brittle fractures on the WC-Co side, while most of the lower part fractured at the interface. Only the joints at 20 μm and 30 μm had a small fracture area on the steel side. Moreover, the fracture on the steel side at 30 μm showed elongated shear dimples, which explains the maximum shear force of the joint at 30 μm.