(Short communication) Degradation of corrosion resistance of Zircaloy-4 in LiOH aqueous solution

To investigate the degradation of corrosion resistance of Zircaloy-4 in LiOHaqueous solution, SIMS (secondary ion mass spectrometry) analysis was performed to examine theprofiles of Li^+, K^+, and OH^- in oxide layers formed in the same concentration (0.1 mol/L) LiOHand KOH solutions. Even though the oxide layers have an equal thickness, the pene-tration depth ofK^+ is shallower than that of Li^+, and the penetration depth of OH^- corroded in KOH solution isalso shal-ower than that corroded in LiOH solution. It shows that the diffusion of OH^- into oxidelayer is accompanied by the corresponding cation. The difference of degradation effect of LiOH andKOH solutions on the corrosion resistance of Zircaloy-4 was discussed.

Sealing Effect of KAl(SO_(4))_(2)Solution on the Corrosion Resistance of Anodized Aluminum Alloy

The 2024 anodized aluminum alloy film was sealed by KAl(SO_(4))_(2)solution and the effect of sealing on corrosion resistance was investigated by means of potentiodynamic polarization curves,electrochemical impedance spectroscopy,and X-ray photoelectron spectroscopy.The experimental results show that the optimal parameters for KAl(SO_(4))_(2)sealing are 35℃,with the pH value of 8,the concentration of 8 g/L,and the sealing time of 3 min.The corrosion resistance of the KAl(SO_(4))_(2)sealed sample can be significantly improved than that of unsealed one,and is obviously superior to that of the conventional hydrothermal sealed sample.Furthermore,X-ray photoelectron spectroscopy demonstrates that more Al(OH)_(3)will be formed in the process of KAl(SO_(4))_(2)sealing,which will shrink the diameter of the microporous and therefore results in the excellent corrosion resistance.

Improvement of the Corrosion Resistance of High Alloyed Austenitic Cr-Ni-Mo Stainless Steels by Solution Nitriding

Characteristic features of austenitic steel grades combine a good corrosion resistance with a low hardness, wear resistance and scratch resistance. An interesting possibility for improving the wear behaviour of these steels without loss of their corrosion resistance lies in enriching the near surface region with nitrogen. The process of a solution nitriding allows the rise of the solution of nitrogen in the solid phase. On this state nitrogen increases the corrosion resistance and the tribilogical load-bearing capacity. The aim of the study was, to investigate the improvement of the pitting corrosion behaviour by solution nitriding. A special topic was to observe the effect of nitrogen by different molybdenum content. So austenitic stainless steels (18% Cr, 12% Ni, Mo gradation between 0.06 to 3.6%) had been solution nitrided. The samples could be prepared with various surface content of nitrogen from 0.04 to 0.45% with a step-by-step grinding. The susceptibility against pitting corrosion of these samples had been tested by determination of the stable pitting potential in 0.5M and 1M NaCl at 25°C. For the investigated steel composition and the used corrosion system there is no influence of molybdenum on the effectiveness of nitrogen. The influence of nitrogen to all of the determined parameters can be described well by PRE = Cr + 3,3 * Mo + 25 *N. XPS analysis of the sample surfaces support the results of the pitting corrosion tests.Additionally surface investigations with an acid elektolyte (0,1M HC1 + 0,4M NaCl) were performed. In this case the passivation effective nitrogen content increases markedly with rising molybdenum concentration of the steel. Obviously an interaction of Mo and N is connected with a strongly acid electrolyte.

Corrosion properties of stainless steel 316L/Ni-Cu-P coatings in warm acidic solution

In order to improve corrosion resistance of stainless steel 316L in warm acidic solution, Ni？Cu？P coatings with high copper and phosphorus contents were deposited onto stainless steel 316L substrates via electroless plating. The structure of the film and its resistance to corrosion in a warm acidic environment were investigated using scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS）, X-ray diffraction spectrometry （XRD）, polarization curves, electrochemical impedance spectroscopy （EIS）, and dipping corrosion tests, respectively. The results demonstrate that Ni？Cu？P coatings consist of two types of nodules, which are 19.98% Cu and 39.17% Cu （mass fraction） respectively. The corrosion resistance of the 316L substrate when subjected to a warm acidic solution is significantly improved by the addition of the new type of the Ni？Cu？P coating. The as-plated coatings demonstrate better corrosion resistance than annealed coatings. As-plated coatings and those annealed at 673 K are found to corrode selectively, while pitting is observed to be the main corrosion mechanism of coatings annealed at 773 and 873 K.

Preparation and Corrosion Resistance of Anodic Oxidation Coatings on 2198 and 5A90 Al-Li Alloys

2198 and 5A90 Al-Li alloys were anodized with a constant DC potential in 18%H_2SO_4solution(Solu.A) and the mixture solution of 18%H_2SO_4+5%C_2H_2O_4(Solu.B) at room temperature. 12 and 11 V was optimized as the applied oxidation potential for 2198 and 5A90 alloys, respectively. Cross-sectional morphology, surface morphology and elements distribution of anodic oxidation coatings were observed by scanning electron microscope equipped with energy dispersive X-ray analysis(SEM/EDX). Corrosion resistance was tested by potentiodynamic polarization plot in 3.5%NaCl solution. The results showed that the thicknesses of coatings obtained at the selected potential in Solu.A and Solu.B were about 50 μm/110 μm for 2198 alloy and 80 μm/110 μm for 5A90 alloy. In both solutions, anodic oxidation coatings of 2198 alloy were primarily composed of Al oxides; those of 5A90 alloy were mainly consisted of Al oxides and a small amount of Mg oxides. The results of potentiodynamic polarization showed that anodic oxidation coatings of 2198 and 5A90 Al-Li alloys had better corrosion resistances than that of untreated alloys.

Effect of Chromium Micro-alloying on the Corrosion Behavior of a Low-carbon Steel Rebar in Simulated Concrete Pore Solutions

A new low-cost corrosion-resistant rebar（HRB400 R） was designed and fabricated by chromium micro-alloying. The effects of Cr on the passivation and corrosion behavior of this rebar in the simulated concrete pore solutions were studied systematically, and its improved corrosion resistance was revealed. In the Cl--free saturated Ca（OH）_2 solution, the HRB400 R rebar presented nearly the same passive film and similar passivation ability compared to the common carbon steel rebar. In the long-term immersion corrosion test in the Cl--contained Ca（OH）_2 solution, the HRB400 R rebar presented improved corrosion resistance and obvious longer passivation-maintaining period. Micro-alloying of Cr element in the rebar matrix enhanced its corrosion resistance against Cl--attack and retarded the corrosion initiation in the matrix. In the alkaline Na Cl salt spraying test, the HRB400 R rebar also presented obviously lower mass-loss rate. The enrichment of Cr element in the rust layer improved its retardant effect to the penetration of aggressive medium, and decreased the corrosion propagation rate of the rebar.

Effects of current density on the corrosion behaviour of anodized aluminum alloy in FeCl_3 solution

In the present study, 2024 aluminum alloy specimen was anodized in acetic acid and oxalic acid e- lectrolytes. Effects of the current density on the microstructure and corrosion resistance of anodic oxide film have been investigated. The steady voltage increases from 11 V to 71 V with the current density increase from 0. 5 A/din2 to 2. 5 A/din2. The SEM reveals that there are pits, cavities and irregular pores in the anodic film, and their size and morphologies change with the current density. The corrosion resistance of the film was evalua- ted by potentiodynamic polarization and electrochemical impedance in 0.1 mol/L FeC13 solution at room temper- ature. The results show that corrosion resistance of the anodic oxide film changes with the current density, and the anodic fihn formed at the current density of 1.0 A/dm2 has the best corrosion resistance. These observations indicate that anodic film formed at J -- 1.0 A/dm2can serve as a support material for the Cu micrometallic pat-

Microstructure evolution and corrosion resistance in simulated CGHAZ of X80 high-deformability pipeline steel

In this study, the microstructure evolution and corrosion resistance in O. 5 M Na2CO3 - 1 M NaHCO3 solution of X80 high-deformability （ X8OHD ） pipeline steel coarse-grained heat-affected zone （CGHAZ） with several heat input levels were investigated. It is shown that the microstructure of CGHAZ changes from bainite ferrite to granular bainite as the heat input increasing. In addition, the corrosion resistance and the stability of passive film of base material are better than those of CGHAZ with several heat input levels. Too small or too big heat input is inadvisable and better corrosion resistance of CGHAZ is attained when heat input is 30 kJ/cm.

Effect of trace boron on corrosion resistance of rust layer of high-strength low-alloy steel in 3.5 wt.% NaCl solution

The influence mechanism of trace boron on the corrosion resistance of high-strength low-alloy(HSLA)steel in a simulated marine environment was studied by combining first-principles calculation with experiment.The effect of boron on the corrosion properties and corrosion morphology of the rust layer formed on the surface of HSLA steel was studied by means of corrosion weightlessness method,polarization curve,scanning electron microscopy(SEM)and X-ray diffraction(XRD)technique.The mass loss measurements and polarization curves revealed that the corrosion resistance of HSLA steel is improved by adding trace boron.XRD and SEM results show that the rust layer is produced byα-FeOOH(the main protective phase),Fe_(3)O_(4) andγ-FeOOH,and boron contributes to stability ofα-FeOOH.Based on the first-principles calculation,the solid solution of B atom in the corrosion product is beneficial to the fixation of Cl atom and to the reduction of the corrosion of Cl atom to the steel matrix.

Valence electron structures and properties of Ni-based corrosion resistant alloy

The corrosion resistance and mechanical properties were tested and compared for the newly synthesized as-cast,as-solution Ni-Cr-Mo-Cu corrosion resistant alloys and 1Cr18Ni9Ti austenitic stainless steel. Their valence electron structural units were constructed,and the relative parameters were calculated by means of the Empirical Electron theory of Solids and Molecules(EET). The results show that,during alloy elements Cr,Mo and Cu entering Ni-matrix,the bonding strength nA and bonding energy EA of the strongest bond of the alloy are greatly increased,causing the stronger solid solution strengthening effects(about 30% increase in σb). Also,as reinforcement of the main bond network and the improvement of stability of the alloy system due to the solution of these alloying elements in γ-Ni,the ionization of metal atoms in corrosion solution and the flow of electrons from anode to cathode would all be impeded during electro-chemical corrosion processes,which leads to the excellent corrosion resistant ability of the present Ni-Cr-Mo-Cu alloy(about 2-3 orders of magnitude as high as 1Cr18Ni9Ti austenitic stainless steel) in several highly aggressive solutions.

纯钛在蒸馏水和Saline溶液中的微动腐蚀行为

采用液压高精度微动试验机研究了球/平面接触纯钛摩擦副在蒸馏水和Saline溶液介质中的微动腐蚀特性.在动力学特性分析的基础上,用激光共焦扫描显微镜(LCSM)观察了磨痕表面形貌并测量了磨损体积.结果表明:蒸馏水和Saline溶液降低了摩擦系数,改变了微动运行区域;干态下的体积磨损量最小,3种介质中的摩擦系数与磨损体积均随位移的增大而增大.微动磨损机制主要表现为粘着与剥落;水基介质中,磨损与腐蚀的交互作用显著加速了钛的材料流失.

Ti6Al4V合金在Saline溶液中的微动腐蚀特性

采用液压高精度微动试验机,做了Ti6A l4V/Si3N4摩擦副在干态、蒸馏水和Saline溶液等3种介质中的微动腐蚀试验,用激光共焦扫描显微镜(LCSM)观察了磨痕表面形貌并测量了磨损体积。结果表明:蒸馏水和Saline溶液改变了微动运行区域;空气中的摩擦因数与磨损体积最大,Saline溶液中最小,3种介质中的摩擦因数与磨损体积均随位移增加而增加;载荷增加时,磨损体积增大而摩擦因数减小;较大位移时,腐蚀与磨损交互作用显著地加速了Ti6A l4V的材料流失;微动损伤主要表现为剥落与磨粒磨损共同作用。

316L不锈钢在Saline溶液中的微动磨蚀行为研究

采用球 -平面接触微动磨损试验设备考察了轧制固溶 31 6L不锈钢在 Saline溶液中的微动磨蚀行为 .研究表明 ,31 6L不锈钢的微动过程存在显著的阶段性 :微动初期为磨合期 ;第一稳定阶段摩擦副处于高摩擦应力状态 ,伴随着不锈钢表面缝隙腐蚀与弹塑性损伤的积累 ;第二过渡阶段和第二稳定阶段不锈钢表面呈微断裂剥层特征 ,腐蚀引起的微断裂不可忽视 .不锈钢微动损伤表面形貌同微动损伤速率之间存在对应关系 .

Effects of single and multi-stage solid solution treatments on microstructure and properties of as-extruded AA7055 helical profile

The effects of single-stage solution treatment(SST),enhanced solution treatment(EST),high-temperature pre-precipitation(HTPP)and multi-stage solution treatment(MST)on the microstructure,mechanical properties and corrosion resistance of the as-extruded 7055 aluminium alloy(AA7055)helical profile were investigated using differential scanning calorimetry(DSC),optical microscopy(OM),scanning electron microscopy(SEM),electron back-scattered diffraction(EBSD)and transmission electron microscopy(TEM).It was observed that EST and MST could promote the dissolution of the second-phase particles compared with the traditional SST,and the intergranular phases were distinctly discontinuously distributed after HTPP and MST.There was obvious difference in the main texture type and texture strength for the alloy after different solid solution treatments.HTPP could improve the corrosion resistance of the alloy by regulating the intergranular phases,but the mechanical properties were severely weakened.While the good corrosion resistance of the alloy could be obtained by MST without obvious strength loss.As a result,the MST is an ideal solid solution treatment scheme for AA7055.

Effect of solid solution treatment on in vitro degradation rate of as-extruded Mg-Zn-Ag alloys

The degradation behaviors of the as-extruded and solution treated Mg-3Zn-xAg(x=0,1,3,mass fraction,%)alloys,as well as as-extruded pure Mg,have been investigated by immersion tests in simulated body fluid(SBF)at37°C.The as-extruded Mg-Zn(-Ag)alloys contained Mg51Zn20and Ag17Mg54.While the quasi-single phase Mg-Zn(-Ag)alloys were obtained by solution treatment at400°C for8h.The quasi-single phase Mg-Zn(-Ag)alloys showed lower degradation rate and more homogeneous degradation than corresponding as-extruded Mg alloys.Degradation rate of solid-solution treated Mg-3Zn-1Ag and Mg-3Zn-3Ag was approximately half that of corresponding as-extruded Mg alloy.Moreover,the degradation rate of solid-solution treated Mg-3Zn and Mg-3Zn-1Ag was equivalent to that of as-extruded pure Mg.However,heterogeneous degradation also occurred in quasi-single phase Mg-Zn-Ag alloys,compared to pure Mg.So,preparing complete single-phase Mg alloys could be a potential and feasible way to improve the corrosion resistance.

Preparation of a single-phase Mg-6Zn alloy via ECAP-stimulated solution treatment

The solution of the intermetallic phase and the homogenization of composition are important for Mg alloy biomaterials.A single-phase Mg-6Zn alloy with the average grain size of about 20μm was prepared by ECAP processed for six passes at 320°C.It indicated that the ECAP could significantly promote the process of solid solution in Mg-Zn alloy.The results showed that complete dissolution of the intermetallic phase improved the corrosion resistance of Mg-6Zn alloy in 0.9%NaCl solution by turning the corrosion behavior into uniform corrosion and increased the hardness in combination with its smaller grain size.

Effect of solution concentration on sealing treatment of Mg-Al hydrotalcite film on AZ91D Mg alloy

Cerium-based sealing treatment was developed for Mg-Al hydrotalcite film on AZ91D Mg alloy,and the influence of cerium salt solution was investigated to modify the surface integrity and corrosion resistance.Scanning electron microscope(SEM)and X-ray diffraction(XRD)measurements were carried out to analyze the surface morphology and phase composition.The corrosion resistance of Mg-Al hydrotalcite film after sealing treatment was evaluated by the polarization curve and electrochemical impedance spectroscopy(EIS)tests.The results showed that lower concentration of Ce-containing solution was beneficial to seal the micro-cracks on Mg-Al hydrotalcite film,and improve the surface integrity and corrosion resistance;higher concentration of Ce-containing solution could seal fewer micro-cracks,and the corrosion resistance was decreased owing to the disintegration of Mg-Al hydrotalcite film.

Anodic Behavior of Zn-Al-Be Alloys in NaCl Solution and the Influence of Be on Structure

Potentiodynamic results of anodic behavior of Zn5Al and Zn55Al alloys, alloyed with Beryllium in the ambience of NaCl electrolyte and their microstructures are studied. They showed that a small addition of Beryllium (0.005 - 0.05 wt%) improves the corrosion resistance of Zn5Al and Zn55Al original alloys to 2 - 3 times by changing grains shape to spherical and changing sizes to small grains. The proposed composition of Zinc-Aluminum alloy, which contains of Beryllium, can be used as anodic coatings to protect steel products and constructions against corrosion.

新标09CrCuSb耐酸钢的耐50%H_(2)SO_(4)腐蚀性能

通过电化学测试和全浸腐蚀试验,研究了不同温度(25,50,60,70℃)条件下新标09CrCuSb耐酸钢在50%H_(2)SO_(4)溶液中的腐蚀行为。结果表明:随着温度从25℃升至70℃,新标09CrCuSb钢的腐蚀速率整体呈现增大趋势,在70℃时,腐蚀速率达到最高,为2.70 g/(m^(2)·h),这与随温度升高,腐蚀产物中具有保护性作用的Fe_(3)O_(4)含量减少,无保护作用的FeSO_(4)·H_(2)O含量增加以及锈层中微孔变化有关。另外,由于新标调整了09CrCuSb钢中Cu、Mo、Sn、Sb、W等元素的含量,与旧标09CrCuSb钢相比,阳极维钝电流密度J维钝降低,同等温度条件下,新标09CrCuSb钢的耐蚀性得到较大改善。