马惠线储罐沉积水中常用管线钢的腐蚀性对比

【目的】通过腐蚀评价进行合理选材,预防新建长输原油管道内腐蚀。【方法】通过腐蚀失重实验,研究X42、X52、X60、X65和X70共5种常用管线钢在马惠线储罐沉积水中的腐蚀行为,并结合SEM和XPS表面分析技术分析其腐蚀产物特性。【结果】随着温度的升高,5种管线钢腐蚀速率先升高后降低,在48℃时腐蚀速率最高。随着流速的增加,腐蚀速率先升高后降低,在流速为0.18m/s时腐蚀速率最大。在静态下,不同钢级管线钢腐蚀速率差别不大,钢级较高的管材点蚀倾向性较高;而在流动的腐蚀环境中,钢级较高的管材耐蚀性相对较高。【结论】综合考虑管线钢的耐腐蚀、耐冲蚀和耐点蚀性能,在马惠线内腐蚀环境中建议选用X60和X65钢。     

考虑腐蚀影响的钢结构轴压构件可靠度预后分析

针对腐蚀会严重影响结构的性能甚至使其崩塌失效这一事实,基于蒙特卡洛方法和Weibull模型提出了钢管轴压构件考虑腐蚀的时变可靠度预测方法.首先利用幂函数模型替代钢材的实际腐蚀过程计算腐蚀厚度,其次利用蒙特卡罗方法计算不同年限时的腐蚀钢管轴压构件的可靠度,同时依据Weibull模型提出钢管在腐蚀作用下的可靠度随时间变化预测曲线.最后通过实际算例验证了所提方法的有效性.结果表明:Weibull模型可以较好地模拟腐蚀影响下的可靠度随时间变化的模型;提出的时变可靠度曲线与理论值吻合较好;考虑腐蚀影响的可靠度值在一定年限以后将会小于目标可靠度.     

表面状态对核级316LN不锈钢电化学腐蚀行为的影响

表征了打磨态和机械抛光态316LN不锈钢表面的粗糙度、表面残余应变和表面电子功函数的分布,并研究了打磨态和机械抛光态样品在硼酸盐溶液中电化学腐蚀行为的差异.与机械抛光态316LN不锈钢相比,打磨处理后样品表面较为粗糙,且表面的微观残余应变较大,近表面产生约50 μm的加工硬化层.表面粗糙度和微观应变的增加引起打磨态表面电化学活性的增大,从而促进316LN不锈钢在硼酸盐溶液中腐蚀.机械抛光处理降低了表面钝化膜的载流子密度(供体和受体),并增大了钝化膜的阻抗,提高了钝化膜的致密性和保护性,能够有效抑制金属的进一步腐蚀.     

σ相对S32760超级双相不锈钢组织和性能的影响

通过对含W的S32760超级双相不锈钢不同温度时效热处理研究σ相的析出行为.用扫描电镜和透射电镜分析σ相的形貌和化学组成,并研究σ相对力学性能和耐腐蚀性能的影响.在850~1000℃之间,实验钢析出大量由Fe-Cr-Mo-W组成的具有正方结构的σ相,钢板强度和硬度高,塑性差,延伸率低于4%;1050℃时仍存在少量析出,虽然延伸率大幅度提高至31.1%,但冲击韧性离散度高,冲击功偏低;直至1080℃,σ相才能完全溶解至基体中,抗拉强度为640 MPa,延伸率为35.5%,纵、横向冲击功平均值分别达到217 J和110 J.随时效热处理温度升高,点蚀电位提高,点蚀失重率不断下降,1080℃热处理的试样点蚀电位高达1246 mV.该试样在50℃的3.5% NaCl溶液中腐蚀失重率也仅为0.005~0.007 g·m-2·h-1.     

超硬铝合金作为阴极在锌电积过程中的电化学行为

选取商业纯铝和超硬铝作为锌电积阴极,在ZnSO4-H2 SO4体系中通过电化学测试研究两种阴极的电化学行为,同时利用扫描电镜观察铝合金上电积锌初期形核,X射线衍射分析锌片结晶取向.研究结果表明：500 A·m-2电流密度下纯铝阴极的析出电位和交换电流密度分别为-1.541 V和7.74×10-11 A·cm-2,超硬铝阴极分别为-1.496 V和6.07×10-3 A·cm-2.合金元素的添加会增加初期形核位置,提高形核速率,而形核速率的提高在一定程度上抑制卤族元素对阴极的腐蚀.沉积3h后,锌片结晶取向没有发生变化.超硬铝易发生烧板和鼓泡,电流效率低,只有84.54%;纯铝电流效率达到88.04%,且沉积锌平整、光滑,但阴极板容易被卤族元素腐蚀.     

Mg-Al和Mg-Li镁合金板在NaCl水溶液中的腐蚀行为

采用电化学方法分别研究了AZ31镁合金轧制板、AZ80镁合金轧制板、ZE42镁合金热挤压板、LZ91镁合金轧制板和LA101镁合金热挤压棒等5种不同的镁合金在质量浓度为5.0%氯化钠水溶液中的腐蚀行为。采用失重法测量每一种合金的腐蚀速率,并且采用扫描电镜(SEM)观察了腐蚀产物的形貌,利用X射线衍射仪(XRD)分析了每种镁合金的相组成。结果表明:电势分布较为均匀的镁合金可减小镁合金的微电偶腐蚀趋势,5种镁合金板(棒)材在NaCl水溶液中的腐蚀速率由低到高的顺序是:AZ80AZ31LA101LZ91ZE42。经36 h浸泡腐蚀后,在NaCl水溶液中镁合金表面主要被腐蚀产物Mg(OH)_2所覆盖,且随着浸泡时间延长,所有镁合金均呈现出明显的点蚀特征,阳极溶解和局部腐蚀程度加重,发生析氢反应,最后变为均匀腐蚀。     

低温电解条件下铝电解用NiFe_2O_4-10NiO基金属陶瓷阳极Fe元素腐蚀行为研究

采用粉末冶金技术制备出铝电解用NiFe2O4-10NiO陶瓷基体和30(40Cu-Ni)/(NiFe2O4-10NiO)金属陶瓷阳极,并在低温电解条件下,对NiFe2O4陶瓷相中Fe元素的腐蚀行为进行研究。结果表明,在烧结过程中,NiFe2O4尖晶石陶瓷基体会在氮气中发生离解,在动态化学腐蚀试验和电解试验中,陶瓷相中的Fe元素更容易进入电解质;电解24h后,铝液中Fe、Ni、Cu的含量分别为0.45%、0.13%和0.03%。     

Corrosion behavior of low alloy steels in a wet–dry acid humid environment

The corrosion behavior of corrosion resistant steel (CRS) in a simulated wet–dry acid humid environment was investigated and compared with carbon steel (CS) using corrosion loss, polarization curves, X-ray diffraction (XRD), scanning electron microscopy (SEM), electron probe micro-analysis (EPMA), N₂ adsorption, and X-ray photoelectron spectroscopy (XPS). The results show that the corrosion kinetics of both steels were closely related to the composition and compactness of the rust, and the electrochemical properties of rusted steel. Small amounts of Cu, Cr, and Ni in CRS increased the amount of amorphous phases and decreased the content of γ-FeOOH in the rust, resulting in higher compactness and electrochemical stability of the CRS rust. The elements Cu, Cr, and Ni were uniformly distributed in the CRS rust and formed CuFeO₂, Cu₂O, CrOOH, NiFe₂O₄, and Ni₂O₃, which enhanced the corrosion resistance of CRS in the wet–dry acid humid environment.     

Conductive and corrosion behaviors of silver-doped carbon-coated stainless steel as PEMFC bipolar plates

Ni–Cr enrichment on stainless steel SS316L resulting from chemical activation enabled the deposition of carbon by spraying a stable suspension of carbon nanoparticles; trace Ag was deposited in situ to prepare a thin continuous Ag-doped carbon film on a porous carbon-coated SS316L substrate. The corrosion resistance of this film in 0.5 mol·L-1 H₂SO₄ solution containing 5 ppm F- at 80℃ was investigated using polarization tests. The results showed that the surface treatment of the SS316L strongly affected the adhesion of the carbon coating to the stainless steel. Compared to the bare SS316L, the Ag-doped carbon-coated SS316L bipolar plate was remarkably more stable in both the anode and cathode environments of proton exchange membrane fuel cell (PEMFC) and the interface contact resistance between the specimen and Toray 060 carbon paper was reduced from 333.0 mΩ·cm2 to 21.6 mΩ·cm2 at a compaction pressure of 1.2 MPa.     

Effects of Fe content on the microstructure and properties of CuNi10FeMn1 alloy tubes fabricated by HCCM horizontal continuous casting

Heating-cooling combined mold (HCCM) horizontal continuous casting technology developed by our research group was used to produce high axial columnar-grained CuNi10FeMn1 alloy tubes with different Fe contents. The effects of Fe content (1.08wt%–2.01wt%) on the microstructure, segregation, and flushing corrosion resistance in simulated flowing seawater as well as the mechanical properties of the alloy tubes were investigated. The results show that when the Fe content is increased from 1.08wt% to 2.01wt%, the segregation degree of Ni and Fe elements increases, and the segregation coefficient of Ni and Fe elements falls from 0.92 to 0.70 and from 0.92 to 0.63, respectively. With increasing Fe content, the corrosion rate of the alloy decreases initially and then increases. When the Fe content is 1.83wt%, the corrosion rate approaches the minimum and dense, less-defect corrosion films, which contain rich Ni and Fe elements, form on the surface of the alloy; these films effectively protect the α-matrix and reduce the corrosion rate. When the Fe content is increased from 1.08wt% to 2.01wt%, the tensile strength of the alloy tube increases from 204 MPa to 236 MPa, while the elongation to failure changes slightly about 46%, indicating the excellent workability of the CuNi10FeMn1 alloy tubes.