Fe-20Cr溅射纳米涂层的腐蚀电化学性能研究

利用电化学方法与表面分析技术 ,考察了平面磁控溅射Fe - 2 0Cr纳米涂层的腐蚀电化学性能及耐蚀机制 .研究表明 ,尽管溅射纳米涂层钝化膜的溶解速度高于铸态合金 ,但其钝化趋势较强 ,即使在含有 0 5mol/LNaCl的H2 SO4溶液中仍能自钝化 ,而此时铸态合金的钝化趋势非常微弱 ;纳米涂层的耐点蚀能力也远优于铸态合金 ;

固溶处理对Mg-6Al-5Pb-1.5In阳极腐蚀电化学性能的影响

在3.5%NaCl(质量分数)溶液中测定铸态和经固溶处理的Mg-6Al-5Pb-1.5In镁合金阳极的腐蚀电化学性能,采用金相(OM)、扫描电镜(SEM)和能谱分析(EDS)分别研究其显微组织、截面腐蚀形貌及相组成。结果表明:固溶后β-Mg17Al12相基本溶入α-Mg基体,降低微电偶腐蚀中阴极与阳极的面积比,增大阳极自腐蚀速率;Mg2Pb相的自腐蚀电位比镁基体正,固溶后Pb以Mg2Pb相析出,阳极表面腐蚀后晶粒中央的Mg2Pb相并没有被腐蚀。Al含量是决定镁阳极中各相腐蚀速率的关键,相表面形成的保护膜中Al含量越高,对基体保护性能越好。

制备工艺对钒基固溶体储氢合金电化学性能的影响分析

为了有效提高铸态钒基固溶体储氢合金的电化学性能,分别采用三种不同的铸造工艺制备了V_3TiNi_(0.56_Sc_(0.1)钒基固溶体储氢合金铸态试样,并进行了显微组织观察以及电化学循环稳定性和电化学腐蚀性能的测试与分析。结果表明:与常规铸造法相比,静置辅助铸造法和双重辅助铸造法有利于改善合金的铸造质量,细化合金晶粒,提高合金的电化学循环稳定性和电化学腐蚀性能,且双重辅助铸造法效果更佳;静置辅助铸造法、双重辅助铸造法分别使放电容量衰减率减小47%、71%,分别使合金的腐蚀电位正移109、237 m V。

钛含量对MgNi储氢合金电化学性能的影响

对添加不同含量Ti的Mg2Ni-Ti储氢合金进行了电化学腐蚀试验和电化学循环稳定性的测试与分析,结果表明:合金元素Ti的添加,有利于提高Mg2Ni合金的电化学腐蚀性能和电化学循环稳定性。合金中Ti含量以0.8%为宜。与不添加Ti的Mg2Ni储氢合金相比,添加0.8%Ti时合金的腐蚀电位正移87 m V,放电容量衰减率从86%减小到47%。

Corrosion behavior of thermal sprayed WC cermet coatings containing metallic binders in saline environment

A series of electrochemical and long-term corrosion tests were carried out in a neutral saline （5%NaCl） vapor of 35 °C on thermal sprayed WC cermet coatings containing different kinds of metallic binders in order to examine the effect of composition of binder materials on the corrosion behavior. The experimental results revealed that the overall corrosion resistance of WC-Co coating was inferior to that of WC-Co-Cr coating. For the coatings without Cr, WC-Co, general corrosion occurred in binder materials in addition to galvanic corrosion between WC particles and metallic binders in the neutral environment. By contrast, the formation of passive film in the form of surface oxide in the coatings containing Cr, WC-Co-Cr, suppressed the binder and metallic binders to be eroded. It is found that the chemical composition of metallic binder materials is one of the important factors influencing the corrosion resistance of HVOF sprayed WC cermet coatings in the neutral vapor.

Effects of surface nanocrystallization on corrosion resistance of β-type titanium alloy

Surface mechanical attrition treatment (SMAT) was performed on biomedicalβ-type TiNbZrFe alloy for 60 min at room temperature to study the effect of surface nanocrystallization on the corrosion resistance of TiNbZrFe alloy in physiological environment. The surface nanostructure was characterized by TEM, and the electrochemical behaviors of the samples with nanocrystalline layer and coarse grain were comparatively investigated in 0.9% NaCl and 0.2% NaF solutions, respectively. The results indicate that nanocrystallines with the size of 10-30 nm are formed within the surface layer of 30 μm in depth. The nanocrystallized surface behaves higher impedance, more positive corrosion potential and lower corrosion current density in 0.9%NaCl and 0.2%NaF solutions as compared with the coarse grain surface. The improvement of the corrosion resistance is attributed to the rapid formation of stable and dense passive film on the nanocrystallized surface of TiNbZrFe alloy.

Effects of Hg and Ga on microstructures and electrochemical corrosion behaviors of Mg anode alloys

The effects of Hg and Ga on the electrochemical corrosion behaviors of the Mg-2%Hg, Mg-2%Ga and Mg-2%Hg-2%Ga (mass fraction) alloys were investigated by measurements of polarization curves, galvanostatic tests and measurements of electrochemical impedance spectroscopy. Scanning electron microscopy, X-ray diffractometry and energy dispersive spectrometry were employed to characterize the microstructures and the corroded surface of the above alloys. The results demonstrate that the microstructure of the Mg-2%Ga alloy is solid solution and the Mg-2%Hg and Mg-2%Hg-2%Ga alloys have white second-phases at the grain boundaries. The Mg-2%Ga alloy has the worst electrochemical activity and the best corrosion resistance, showing a mean potential of -1.48 V and a corrosion current density of 0.15 mA/cm2. The Mg-2%Hg-2%Ga alloy has the best electrochemical activity and the worst corrosion resistance, showing a mean potential of -1.848 V and a corrosion current density of 2.136 mA/cm2. The activation mechanism of the Mg-Hg-Ga alloy is dissolution-deposition of the Hg and Ga atoms.

Mechanical and electrochemical characteristics in sea water of 5052-O aluminum alloy for ship

The optimum corrosion protection potentials were examined for 5052-O Al alloy,which is mainly used in ships.Various electrochemical experiments were carried out and the surface morphologies of specimens were observed by scanning electron microscopy（SEM） in order to determine the optimum corrosion protection potential to overcome pitting,corrosion,stress corrosion cracking（SCC）,and hydrogen embrittlement in sea water.An optimum protection potential range of-1.3 V to-0.7 V was determined under the application of an impressed current cathodic protection（ICCP） system.The low current densities were shown in the range of-1.3 V to-0.7 V in the electrochemical experiments and good specimen surface morphologies were observed after potentiostatic experiment.

Comparative study on microstructure and electrochemical corrosion resistance of Al7075 alloy prepared by laser additive manufacturing and forging technology

Al7075 alloy is a typical aviation aluminum with good mechanical properties and anodic oxidation effect.Laser engineered net shaping technology has unique advantages in the integrated forming of high-performance large aircraft structural parts.The manufacturing of 7075 aluminum alloy structural parts by laser engineered net shaping technology has become an important development direction in the future aerospace field.Electrochemical corrosion resistance of aluminum alloys is of vital importance to improve reliability and life-span of lightweight components.A comparative study on microstructure and anti-corrosion performance of Al7075 alloy prepared by laser additive manufacturing and forging technology was conducted.There are hole defects in LENS-fabricated Al7075 alloy with uniformly distributedηphase.No defects are observed in Al7075 forgings.The large S phase particles and small ellipsoidalηphase particles are found in Al matrix.The corrosion mechanisms were revealed according to the analysis of polarization curves and corrosion morphology.It was found that compared with that prepared by forgings,the additive manufactured samples have lower corrosion tendency and higher corrosion rate.Corrosion occurred preferentially at the hole defects.The incomplete passivation film at the defects leads to the formation of a local cell composed of the internal Al,corrosion solution and the surrounding passive film,which further aggravates the corrosion.

Effect of rolling processing on microstructure and electrochemical properties of high active aluminum alloy anode

The effect of rolling processing on the microstructure,electrochemical property and anti-corrosion property of Al-Mg-Sn-Bi-Ga-In alloy anode in alkaline solution(80℃,Na2SnO3+5 mol/L NaOH)was analyzed by the chronopotentiometry (E-T curves),hydrogen collection tests and modern microstructure analysis.The results show that when the rolling temperature is 370℃,the electrochemical activity of Al anode decreases gradually with the increase of pass deformation in rolling,while the anti-corrosion property is improved in the beginning and then declined rapidly.When the pass deformation of rolling is 40%,the Al anode has good electrochemical activity as good as the anti-corrosion property and with the increase of rolling temperature,both electrochemical activity and anti-corrosion property of Al anode increase first and then decrease.When the rolling temperature is 420 ℃,the aluminum alloy anode has the most negative electrode potential of about-1.521 V(vs Hg/HgO)and the lowest hydrogen evolution rate of 0.171 6 mL/(min·cm2).The optimum comprehensive performance of Al alloy anode is obtained.

Effect of temperature on copper corrosion in high-level nuclear waste environment

The effect of temperature on the corrosion behavior of copper in simulated high-level nuclear waste environment wassystematically studied.Electrochemical methods,including electrochemical impendence spectra,Mott–Schottky technology,cyclicpolarization,and potentiostatic polarization,were employed to characterize the corrosion behavior of copper at different temperatures.Stereoscopic microscopy and scanning electron microscopy were used to examine the surface morphology,and X-ray photoelectronspectroscopy analysis was used to identify the composition of the passive film.The experimental results show that corrosionresistance of the passive film does not blindly decrease with the increase of temperature but increases at60°C owing to a compactouter layer;there is a potential for pitting corrosion,which decreases as the temperature increases.The main product of copper in ananaerobic aqueous sulfide solution is Cu2S but the content of CuS increases at higher temperatures.The whole passivation rangeshows p-type semiconductor characteristics and the magnitude of the acceptor density is1023cm-3,which increases with increasingtemperature.

Effect of thermo-mechanical processing on microstructure and electrochemical behavior of Ti-Nb-Zr-V new metastable β titanium biomedical alloy

The influence of thermo-mechanical processing (TMP) on the microstructure and the electrochemical behavior of new metastableβ alloy Ti?20.6Nb?13.6Zr?0.5V (TNZV) was investigated. The TMP included hot working in belowβ transus, solution heat treatments at the same temperature and different cooling rates in addition to aging. Depending upon the TMP conditions, a wide range of microstructures with varying spatial distributions and morphologies of equiaxed/elongatedα andβ phases were attained, allowing for a wide range of electrochemical properties to be achieved. The corrosion behavior of the studied alloy was evaluated in a Ringer’s solution at 37 °C via open circuit potential?time and potentiodynamic polarization measurements.

Optimization of Cr/Mo molar ratio in FeCoCrMoCBY alloys for high corrosion resistance

The corrosion behavior of bulk metallic glasses(BMGs)(Fe41Co7Cr15Mo14C15B6Y2)100-xCrx(x=0,4,8,12,molar fraction,%)was investigated in1mol/L HCl aqueous solution with electrochemical tests.The electrochemical measurements demonstrate that the passive current density of Fe-based amorphous alloy is reduced by about one order of magnitude,and meanwhile,the stability of passive film can be guaranteed by the Cr/Mo molar ratio.The Mott–Schottky(M–S)curves show that the passive film is the densest when the molar ratio of Cr/Mo is between1.37and1.69.X-ray photoelectron spectroscopy(XPS)analysis was performed to clarify chemical states of elements in the passive films.The results show that the corrosion resistance of the alloy is related to the molar ratio of Cr/Mo.The stability of passive film is determined by the synergistic action of Cr and Mo elements.The main component of the passive film is Cr3+oxide.When the potential is greater than0.5V(vs SCE),Mo6+ions play an important role in keeping the stability of the passive film.The appropriate molar ratio of Cr/Mo can reduce the dissolution rate of the passive film.

Corrosion performance of zinc coated steel in seawater environment

Considering the continuous exploitation of marine resources, it is very important to study the anticorrosion performance and durability of zinc coated streel （ZCS） because its increasing use as reinforcements in seawater. Tafel polarization curves and linear polarization curves combined with electrochemical impedance spectroscopy （EIS） were employed to evaluate the corrosion performance of ZCS at Qingdao test station during long-term immersion in seawater. The results indicated that the corrosion rate of the ZCS increased obviously with immersion time in seawater. The corrosion products that formed on the zinc coated steel were loose and porous, and were mainly composed of Zn5（OH）8C12, Zn5（OH）6（CO3）2, and ZnO. Pitting corrosion occurred on the steel surface in neutral seawater, and the rate of ZCS corrosion decreased with increasing pH.