Damage mechanism at different transpassive potentials of solution-annealed 316 and 316l stainless steels

Electrochemical impedance spectroscopy (EIS), anodic polarization and scanning electron microscopy techniques were used to investigate the damage mechanism in the transpassive potential region of AISI ...     

Corrosion behavior of air plasma spraying zirconia-based thermal barrier coatings subject to Calcium–Magnesium–Aluminum-Silicate (CMAS) via burner rig test

Three different kinds of thermal barrier coatings (TBCs) — 8YSZ, 38YSZ and a dual-layered (DL) TBCs with pure Y₂O₃ on the top of 8YSZ were produced on nickel-based superalloy substrate by air plasma spraying (APS). The Calcium–Magnesium–Aluminum-Silicate (CMAS) corrosion resistance of these three kinds of coatings were researched via burner rig test at 1350 °C for different durations. The microstructures and phase compositions of the coatings were characterized by SEM, EDS and XRD. With the increase of Y content, TBCs exhibit better performance against CMAS corrosion. The corrosion resistance against CMAS of different TBCs in descending was 8YSZ + Y₂O₃, 38YSZ and 8YSZ, respectively. YSZ diffused from TBCs into the CMAS, and formed Y-lean ZrO₂ in TBCs because of the higher diffusion rate and solubility of Y³⁺ in CMAS than Zr⁴⁺. At the same time, 38YSZ/8YSZ + Y₂O₃ reacts with CAMS to form Ca₄Y₆(SiO₄)₆O/Y_4·67(SiO₄)₃O with dense structure, which can prevent further infiltration of CMAS. The failure of 8YSZ coatings occurred at the interface between the ceramic coating and the thermally grown oxide scale (TGO)/bond coating. During the burner rig test, the Y₂O₃ layer of the DL TBCs peeled off progressively and the 8YSZ layer exposed gradually. DL coatings keep roughly intact and did not meet the failure criteria after 3 h test. 38YSZ coating was partially ablated, the overall thickness of the coating is thinned simultaneously after 2 h. Therefore, 8YSZ + Y₂O₃ dual-layered coating is expected to be a CMAS corrosion-resistant TBC with practical properties.     

规整有机分子自聚集体对铜的高效缓蚀的研究

通过多步法合成了离子型含双苯并三氮唑环的目标分子，4，4'-{苯-1，3-二基二[(1E)-3-羰基丙-1-烯-1，3-二基]}二[2-(2H-苯并三唑-2-基)苯醇酸]二钾。在室温条件下，目标分子在3.5%（质量）NaCl/DMSO（二甲基亚枫）混合溶液 （体积比：40/60） 中能够发生分子自组装产生纳-微米级的自聚集体。通过傅里叶变换红外光谱 （FT-IR）、拉曼光谱和X射线光电子能谱 （XPS） 的表征，证实了所形成的目标分子自聚集体能够对铜表面产生强烈的化学吸附作用，在铜表面形成自组装膜。利用电化学方法测定了目标分子自聚集体吸附在铜表面形成自组装膜后，在3.5%（质量）NaCl溶液中的缓蚀性能。结果表明目标分子自聚集体在NaCl溶液中能高效地抑制铜腐蚀。     

Chitosan Microspheres as Carriers for pH‐Indicating Species in Corrosion Sensing

Chitosan microspheres containing bromocresol green, cresol red, and phenolphthalein for corrosion detection, through pH change, are synthesized in order to be used in protective coatings for aluminium alloys. Microspheres containing corrosion detection species are characterized morphologically (SEM) and physico‐chemically (FTIR, TGA). Release studies (UV–vis) are performed in corrosion‐promoting conditions (pH, NaCl), and detection studies by immersion in media associated with corrosion activity while microspheres' sensing activity is evaluated visually. Electrochemical characterization of AA2024 substrates in the presence of chitosan spheres is performed to understand material performance, and a color change is observed as a result of local pH increase in cathodic areas when corrosion takes place. These findings can be correlated with the results from release studies and seem a promising approach for corrosion sensing purposes, not only because pH increase is possible to detect due to corrosion, but also because chitosan is considered an environmentally friendly material.     

伞帽用高铬铸铁在热强碱腐蚀环境下的磨损分析

针对氧化铝行业中常用的Cr28和Cr20高铬铸铁伞帽在相同工况条件下的磨损机理进行分析,并对比研究了实际生产中两种失效材料的成分、组织及性能。结果表明,伞帽部件在高温强碱腐蚀条件下受到外界冲刷时,磨损量由微切削磨损与变形磨损这两种机制共同决定。含铬量较高的Cr28高铬铸铁,其冲刷和抗腐蚀磨损性能均优于Cr20高铬铸铁。伞帽服役寿命主要受浆料和表层的铸铁材料两大因素影响。两种试验材料经淬火+回火处理后,基体组织中主要为回火马氏体+M₇C₃型碳化物+少量残留奥氏体,其中含铬量较高的Cr28高铬铸铁中共晶碳化物含量更高,且分布更加弥散,其平均硬度值为64.0 HRC,高于Cr20高铬铸铁的60.2 HRC。最终确定Cr28高铬铸铁作为伞帽材质更能满足氧化铝生产及设备检修周期的需要。     

Corrosion behaviors of Cr2AlC/α-Al2O3 composites in 3.5 wt. % NaCl aqueous solution

Cr₂AlC and its composites containing α-Al₂O₃ (6.1 and 15.2 wt %) were prepared by hot pressing and their corrosion behaviors in air-saturated 3.5 wt % NaCl aqueous solution were investigated by electrochemical testing methods. It was revealed that the secondary phase of Al₂O₃ particles mainly distributed along grain boundaries of Cr₂AlC matrix. The potentiodynamic polarization measurements showed that the corrosion current densities of these Cr₂AlC composites were lower than that of the pure Cr₂AlC. The Aluminum in Cr₂AlC was prone to be attacked more easily. When immersed at open circuit potential (OCP), Al readily slipped out from Cr₂AlC matrix into NaCl solution in the form of dissoluble species. But in the case of polarization, regardless of potentiostatic polarization or potentiodynamic polarization, more de-intercalated Al, reacted with the electrolyte to form corrosion products of Al₂O₃ and/or AlOOH and deposited on the sample surface. For Cr₂AlC/α-Al₂O₃ composites, the presence of Al₂O₃ weakened the corrosion along grain boundaries by partly blocking the permeation of electrolyte and inhibiting the anodic dissolution process.     

Investigation of the influence of iron-containing abrasives on the corrosion behaviour of the aluminium alloy AlSi1.2Mg0.4

The corrosion resistance of aluminium surfaces is closely linked to the surface state after a grinding process. For years, iron-containing abrasive materials were suspected to lead to increased corrosion susceptibility after processing of aluminium surfaces. To prove a possible correlation between the iron content of an abrasive and the corrosion behaviour of aluminium components, scientific investigations and experimentally practical corrosion tests are necessary. For the current investigation, specimens of a technical Al-Si alloy from the same batch were used. The test specimens were mechanically ground with various resin-bonded model abrasives containing different iron contents. The performed corrosion tests did not reveal a negative influence of the different iron-containing abrasives on the corrosion behaviour of the Al–Si alloy. However, the most sensitive measuring method (electrochemical noise) showed differences in the surface activity depending on the type of abrasive.     

超疏水表面在金属防护中应用的研究进展

超疏水表面由于具有独特的微纳米粗糙结构和低表面能性质,能形成空气垫物理屏障层,减小材料表面与水或其他腐蚀介质之间的接触面积,因此被广泛应用于金属的腐蚀防护。首先简单介绍了超疏水表面的相关理论,主要包括Young氏方程、Wenzel模型和Cassie-Baxter模型。然后,归纳总结了三种制备超疏水表面的有效途径:在低表面能物质上构建微纳米级粗糙结构;先构建出具有微纳米级的粗糙结构,再对表面进行低表面能修饰;一步法完成低表面能修饰和微纳米级粗糙结构的构建。在此基础上,详细地综述了常见的超疏水表面(薄膜或涂层)在金属防护中的应用。进一步介绍了通过在超疏水体系中引入缓蚀剂的方式,构建具有主动防护功能的超疏水表面,并介绍了此种超疏水表面在金属防护中的应用。最后指出了目前的超疏水表面在制备工艺以及耐久性等方面存在的问题,并对其在金属防护领域的应用前景和发展方向作出了展望。