动态与静态纯腐蚀对定量研究材料冲刷腐蚀交互作用的影响

分别测定了不锈钢和碳钢静态与动态纯腐蚀失重率、冲刷腐蚀失重率及其电化学行为,研究了静态与动态纯腐蚀失重率对材料冲刷腐蚀交互作用失重率的影响,实验表明:(1)动态纯腐蚀比静态纯腐蚀更能反映材料在液固两相流中冲刷腐蚀交互作用的本质:(2)本实验条件下．T8钢动态纯腐蚀失重率是静态纯腐蚀失重率的2倍以上．18-8不锈钢动态纯腐蚀失重率竟是静态纯腐蚀失重率200倍以上．静态交互作用失重率是动态交互作用失重率的2倍以上,可见静态与动态纯腐蚀对定量研究材料冲刷腐蚀交互作用会产生很大的差异:(3)在腐蚀性浆料中．首先要保证材料具有一定的耐蚀性,其次再考虑提高材料的硬度和耐磨性．这样才能有效地提高材料的耐冲刷腐蚀性能,对不同的工况,必须同时兼顾材料的耐蚀性和耐磨性。

碳钢在模拟海水中腐蚀行为的研究

测定了低碳钢在静态与流动的模拟海水纯腐蚀失重率及其电化学行为,研究表明:动态比静态纯腐蚀失重率大,腐蚀速度随温度与流速的增大而增大。

Electrochemical and corrosion behaviors of pure Mg in neutral 1.0% NaCl solution

The corrosion behaviors and corresponding electrochemical impedance spectroscopy（EIS） and polarization curves of pure Mg in neutral 1.0% NaCl solution were investigated.The fractal dimension of EIS at different time was studied.The corrosion process and EIS evolution are divided into three stages.In the initial stage,EIS is composed of two overlapped capacitive arcs,the polarization resistance and charge transfer resistance increase rapidly with immersion time,and the corrosion rate decreases.Then,two well-defined capacitive arcs appear,and the charge transfer resistance and corrosion rate remain stable.After a long immersion time,inductive component appears in a low frequency range,the charge transfer resistance decreases and the corrosion rate increases with the immersion time.The fractal dimension obtained from the time records of EIS seems to be a promising tool for the analysis of corrosion morphology because of its direct relationship with the metal surface.

Study of the Corrosion Resistance of Electroless Ni-P Deposits in a Sodium Chloride Medium

The corrosion resistance of electroless Ni-P deposits with phosphorous contents from 12% to 14% in sodium chloride solutions was studied. The deposits were immersed in 3.5% NaCl solutions for 29 d to obtain the electrochemical parameters and were examined in a standard salt spray test for 15 d respectively. The corrosion resistance of the deposits was studied by poten- tio-dynamic scan, electrochemical impedance spectroscopy (EIS), X-ray diffraction (XRD) and cold-field emission scanning electron microscopy (FE-SEM) equipped with an energy dispersive X-ray detector (EDX). The patterns of XRD and the results of FE-SEM showed that the prepared deposits were amorphous. But after a 15 d standard salt spray test, a few pinholes appeared on the surface of the deposit and the weight content of phosphorus on the surface of the deposit was higher (which was beneficial to the formation of the passivation films) than that before the standard salt spray test when the nickel content was lower because the dissolved weight of nickel was greater than that of phosphorus. The results from potentio-dynamic scan and EIS showed that passivation films formed on the Ni-P deposit after immersion in the NaCl solutions, which decreased the corrosion rate of Ni-P samples. The results of this work show their potential applications in marine corrosion.

Effect of plane surface and wrinkly surface of pure Titanium on corrosion resistance and bacterium accumulation: an in vivo study

Objective: To study the effect of surface configuration on the corrosion resistance and bacterium accumulation of pure Titanium(Ti) when used in oral environment. Methods: Six edentulous volunteers with healthy oral mucosa participated in an in vivo study. Two kinds of pure Ti testing pieces with plane and wrinkly surface were fixed in the polished surface of upper complete dentures. After 6-month wearing, dynamic polarization curves were traced with electrochemical method and the amount and species of bacterium adhered on pure Ti were examined. Results: ① Ep and Ip of specimen in oral cavity was higher than that left in air, which meant corrosion resistance falling. Compared to plane one, Ecorr of wrinkly specimen was more positive and Ep and Ip were more higher, so its corrosion resistance reduced. ② Individual difference put a significant influence on amount of bacterium adhered on pure Titanium, but had no relation to species of bacterium. To the same patient, wrinkly samples collected more bacterium than plane ones, and exhibited G - coccus beside G + coccus. Conclusion: From the perspective of corrosion behavior and benefit to periodontal tissue, wrinkly surface should not be adopted when pure Ti prosthesis is made,especially on connector part of denture.

辽宁地区混凝土桥梁耐久性检验与评价研究

气候变化、冻融循环、除雪剂与海水氯腐蚀介质等因素会加速混凝土破坏,为研究辽宁地区混凝土桥梁耐久性,通过纯冻融和盐腐蚀两种混凝土冻融环境耐久性检验进行研究,并根据实桥检测结果进行验证。结果表明:修正后的评价指标基本符合现场检测结果。冻融与氯盐共同环境对钢筋锈蚀作用最明显,冻融环境对钢筋锈蚀作用次之,氯盐环境对钢筋锈蚀作用最轻。研究结果为辽宁地区不同环境条件下的混凝土桥梁养护维修方案提供参考。

Effects of surface roughness on corrosion resistance of pure Titanium:An in vivo observation

Objective： To study the effect of surface configuration and roughness on the corrosion resistance of pure Titanium （Ti） after used in oral environment for half a year. Methods ：Three edentulous volunteers with healthy oral mucosa participated in an in vivo study. Four kinds of pure Ti testing pieces with different surface roughness were fixed in the polished surface of upper complete dentures and the other in the tissue surface of the dentures. After 6-month wearing the denture, dynamic polarization curves were traced with electrochemical method. Results：Ep and Ip of specimen used in oral cavity was higher than that left in air,which meant corrosion resistance falling. Compared to plane one ,Ecorr of wrinkly specimen was more positive,and Ep and Ip were more higher,so its corrosion resistance reduced. With the increase of surface roughness,Ep and Ip increased from 0.937 V and 1.810μA （Group Ⅱ） to 1.701 V and 2.252μA （Group Ⅳ）respectively,there was even no passivation in Group Ⅲ （which was the most coarse）,so proneness to corrosion enhanced. For specimen with the same surface roughness ,Ep and Ip of Group Ⅳ （1.701 V and 2.252 μA respectively） ,which was placed on polished surface of denture base,was higher than that on tissue surface（Group V , 1. 304 V, 1. 946μA）. Conclusion： From the perspective of corrosion behavior, wrinkly surface should not be adopted when pure Ti prosthesis is used,and surface roughness on the polishing surface of pure Ti prosthesis should be paid more attention,especially on clasps and connectors, where there is often more force to be exerted.

Corrosion Resistance Enhancement of Pure Zirconium in Various Environments via Microstructure Tailoring

The corrosion properties of pure zirconium(Zr)with different grain sizes in acid,alkali,and salt environments were studied.The microstructures of pure Zr were observed by optical microscope,X-ray diffractometer,and electron backscattered diffraction probe.The corrosion resistance of pure Zr was analyzed by electrochemical corrosion test and immersion test.Results show that pure Zr with grain size of 4–32μm can be obtained after annealing at 800°C for different durations,and the relationship between grain size and annealing duration is D^(3)−D_(0)^(3)=3.35t.The electrochemical corrosion and immersion corrosion test results show that the pure Zr with grain size of about 24μm(annealing at 800°C for 20 h)possesses the optimal corrosion resistance.

“Petal effect”-inspired superhydrophobic and highly adhesive coating on magnesium with enhanced corrosion resistance and biocompatibility

With properties of complete degradation and favorable mechanical behavior, Mg and its alloys are regarded as the next generation medical metal materials. However, fast degradation and poor surface biocompatibility hinder their clinical applications. Inspired by the ＂petal effect＂, we successfully constructed a superhydrophobic and highly adhesive coating on pure Mg via a simple hydrothermal treatment in a solution containing sodium oleate. The superhydrophobicity of the fabricated coating results from its flake-like micro-nanostructure and the low-surface-energy oleate group. Water droplet on the superhydrophobic coating cannot roll off even when the sample is turned upside down, owing to the sealed air-pockets and the van der Waals’ attraction at the solidliquid interface, indicating a highly adhesive force. The chemical and mechanical stability of the superhydrophobic coating were measured. Potentiodynamic polarization and electrochemical impedance spectroscopy measurements suggest enhanced corrosion resistance of the as-prepared sample.Furthermore, cell cytotoxicity, migration and adhesion data of human umbilical vein endothelial cells（HUVECs） reveal an improved cytocompatibility of the modified surface. Finally,hemolysis assay and platelet adhesion assay suggest an improved hemocompatibility. It is believed that the facile and low-cost method can expand the new application of superhydrophobic surface with highly adhesive on Mg in biomedical fields.