共查询到20条相似文献,搜索用时 15 毫秒
1.
Mohammad Shoeb Ahmed Paul Munroe Zhong-Tao Jiang Xiaoli Zhao William Rickard Zhi-feng Zhou Lawrence Kwok Yan Li Zonghan Xie 《Corrosion Science》2011,53(11):3678-3687
Nanocomposite TiSiN coatings were deposited on tool steels. Detailed mechanisms that govern the corrosion of these coated steels were revealed, following immersion tests in a 70% nitric acid solution. Pitting originated preferentially from coating defect sites and expanded with increasing immersion time. Both Young’s modulus and hardness measured by nanoindentation decreased as the corrosion damage intensified. A thin oxide layer formed from the thermal annealing of the as-deposited samples at 900 °C was found to be effective against corrosive attack. In addition, compressive residual stress was noted to suppress the propagation of corrosion-induced cracks. The role of residual stress in controlling the corrosion resistance of these ceramic-coated steels is clarified by finite element analysis. 相似文献
2.
The influence of silicon carbide (SiCp) proportion and matrix composition on four aluminium metal matrix composites (A360/SiC/10p, A360/SiC/20p, A380/SiC/10p, A380/SiC/20p) immersed in 1-3.5 wt% NaCl at 22 °C was investigated by potentiodynamic polarization. The kinetics of the corrosion process was studied on the basis of gravimetric measurements. The nature of corrosion products was analysed by scanning electron microscopy (SEM) and low angle X-ray diffraction (XRD). The corrosion damage in Al/SiCp composites was caused by pitting attack and by nucleation and growth of Al2O3 · 3H2O on the material surface. The main attack nucleation sites were the interface region between the matrix and the reinforcement particles. The corrosion process was influenced more by the concentration of alloy elements in the matrix than by the proportion of SiCp reinforcement and saline concentration. 相似文献
3.
The corrosion behaviour of an HVOF Ni–5Al/WC–17Co coating on Al-7075 is investigated in 0.5 M H2SO4. In the temperature range of 25–45 °C, the coating exhibits pseudopassivity that effectively protects from localized corrosion. At 25 °C, pseudopassivity proceeds via three stages: during the first stage, oxidation of W in the binder phase occurs. The second stage is characterized by oxidation of W in both the binder and the carbide particles. The third stage is characterized by intensive hydration of WO3 and formation of Co3O4. During the second and third pseudopassive stages, the formation of a bi-layer surface film is postulated. The inner layer, consisting of anhydrous oxides, has a barrier character. The outer layer, composed of WO3 · xH2O, is unstable. In case of surface film disruption, the bond coat successfully hinders corrosion propagation into the Al-alloy. Higher electrolyte temperatures lead to faster corrosion kinetics and higher tendency for pitting. 相似文献
4.
NiTi alloy is here investigated as an alternative coating to stainless steel since it is considered to possess good corrosion properties. Three different thermal spray techniques (high velocity oxy-fuel -HVOF-, vacuum plasma spray -VPS- and atmospheric plasma spray quenching -APS+Q-) have been used for building the coatings, and electrochemical tests have been carried out for corrosion evaluation. Open-circuit tests have revealed that the VPS-coating shows fairly good corrosion resistance, both in the as-sprayed and polished forms. The HVOF coatings however, showed a strong dependence on the surface conditions and APS+Q is dominated by electrolyte penetration through coating cracks, thus exhibiting a higher icorr. 相似文献
5.
TiC particle-reinforced 304 stainless steels were prepared using a new developed in situ technology and their corrosion behavior was compared with that of 304SS in 5 wt.% HCl solution. As compared to 304SS, Ecorr, Epit and Erp values had shifted to a more negative region in 304SS containing TiC, indicating faster corrosion rate by TiC addition. The addition of TiC particles to 304SS resulted in no rapid pit propagation but maintained a high corrosion rate in the whole immersion time investigated. 相似文献
6.
M. Carboneras 《Corrosion Science》2010,52(3):761-768
Thermally sprayed Al and Al/SiCp composite coatings have been deposited on ZE41 magnesium alloy and mechanical compaction at room temperature was applied to the Al and Al/SiCp coatings to reduce their porosity. Corrosion behaviour of coated samples was evaluated and compared to that of uncoated substrate in 3.5 wt.% NaCl solution using electrochemical measurements. Al and Al/SiCp composite coatings reduced the corrosion current density of Mg-Zn alloys by three and two orders of magnitude, respectively, and reductions up to four orders of magnitude were obtained after mechanical compaction. 相似文献
7.
The effect of corrosive environment on corrosion fatigue crack growth (CFCG) behavior of oil-grade nickel-base alloy 718 is studied. The results demonstrate that there is no obvious effect of 3.5 wt.% NaCl solution at RT, 50 °C and 80 °C on CGCG rates while 21 wt.% NaCl solution at 80 °C produces a deleterious effect on CFCG rates compared to the ones tested in air. Potentiodynamic polarization results show that alloy 718 exhibits passive behavior in 3.5 wt.% NaCl solution, while pitting corrosion resistance decreases with increasing solution temperature. Nevertheless, alloy 718 shows active corrosion behavior in 21 wt.% NaCl solution at 80 °C. 相似文献
8.
The transition from metastable to stable pitting was studied in 0.5 M NaCl water solution for two cast duplex stainless steels under different microstructural conditions achieved by annealing in the range from 900 °C to 1200 °C. The ensuing microstructural changes in heat treated steels were defined and correlated with established pitting potentials (Ep) and sites of corrosion damage initiation. The variations in Ep have been discussed in terms of secondary phases precipitation. The critical condition for pit stability was quantified and used to select an appropriate microstructural state, resulting in the higher potential at which stable pit growth is first observed. 相似文献
9.
Corrosion behavior of closed-cell AZ31 foam in different concentrations of NaCl solutions is investigated, using commercial AZ31 magnesium alloy as comparison. Mathematical models and expressions are established to calculate surface areas of the foams. Microstructure observation, hydrogen evolution and potentiodynamic polarization are applied to characterize the corrosion behaviors. Results show that foams possess higher corrosion resistance than commercial AZ31 magnesium alloy. In addition, the mathematical models and expressions are confirmed to be simple and effective in calculating surface areas (expose to corrosive medium) of closed-cell metal foams. 相似文献
10.
Dalei Song Xiaoyan Jing Jun Wang Yanli Wang Piaoping Yang Ming Zhao Milin Zhang 《Corrosion Science》2011,(5):1732-1737
Here we report a novel approach of hot-pressing, adapted to assembly ZSM-5 (Zeolite Socony Mobile-Five) coatings on Mg–Li alloy. X-ray diffraction (XRD) patterns and scanning electron microscopy (SEM) images show that ZSM-5 coatings are uniform and compact. The ZSM-5 exhibits a pure MFI structure. The corrosion behaviors of Mg–Li alloy and ZSM-5 coatings are investigated by electrochemical and immersion tests. The results indicate that ZSM-5 coatings improved the corrosion resistance of Mg–Li alloy, which is related to templates blocking the pores of ZSM-5. The concept of hot-pressing introduced here may be helpful to assemble uniform coatings on other substrates. 相似文献
11.
The corrosion behaviour of silicon-carbide-particle (SiCp) reinforced AZ92 magnesium alloy manufactured by a powder metallurgy process was evaluated in 3.5 wt.% NaCl solution, neutral salt fog (ASTM B 117) and high relative humidity (98% RH, 50 °C) environments. The findings revealed severe corrosion of AZ92/SiC/0-10p materials in salt fog environment with formation of corrosion products consisting of Mg(OH)2 and (Mg,Al)x(OH)y. The addition of SiCp increased the corrosion rate and promoted cracking and spalling of the corrosion layer for increasing exposure times. Composite materials revealed higher corrosion resistance in high humidity atmosphere with almost no influence of SiCp on the corrosion behaviour. 相似文献
12.
Cr3C2-NiCr thermal spray coatings are extensively used to mitigate high temperature erosive wear in fluidised bed combustors and power generation/transport turbines. The aim of this work was to characterise the variation in oxide erosion response as a function of the Cr3C2-NiCr coating microstructure. Erosion was carried out at 700 °C and 800 °C with erodent impact velocities of 225-235 m/s. The erosion behaviour of the oxide scales formed on these coatings, was influenced by the coating microstructure and erosion temperature. Development of the carbide microstructure with extended heat treatment lead to variations in the erosion-corrosion response of the Cr3C2-NiCr coatings. 相似文献
13.
In order to evaluate stress corrosion cracking (SCC) susceptibility of Zr-based bulk glassy alloys and develop the BGAs with low susceptibility to SCC, the SCC behaviour of Zr50Cu40Al10, Zr50Cu30Al10Ni10 and hypoeutectic Zr70Cu6Al8Ni16 BGAs in various environments including sodium chloride solution has been investigated using a slow strain rate technique at an initial strain rate of 5 × 10−6 s−1. It is found, for the first time, that the Zr70Cu6Al8Ni16 BGA has no susceptibility to SCC in a 0.5 M NaCl solution. On the other hand, Zr50Cu40Al10 and Zr50Cu30Al10Ni10 BGAs are highly susceptible to SCC in the NaCl solution, although they are not susceptible to SCC in de-ionized water, phosphate buffer, 0.5 M Na2SO4 and 0.5 M NaNO3 solutions. The possible cause of the high susceptibility to SCC in the NaCl solution for the Zr50Cu40Al10 and Zr50Cu30Al10Ni10 BGAs is discussed. 相似文献
14.
The effects of solution heat-treatment and shielding gas on the pitting corrosion of hyper duplex stainless steel (HDSS) welds were investigated in highly concentrated chloride environments. The pitting resistance of a solution heat-treated HDSS after welding with an Ar shielding gas supplemented with N2 was greatly increased due to the dissolution of Cr2N in α-phase, which followed the diffusion of N atoms from the α-phase to the γ-phase and an increase of the γ-phase in the weld metal and heat affected zone. It was also attributed to a decrease of the pitting resistance equivalent number difference between the two phases. 相似文献
15.
Influence of Ce surface treatments on corrosion behaviour of A3xx.x/SiCp composites in 3.5 wt.% NaCl
A. Pardo M.C. Merino R. Arrabal F. Viejo M. Carboneras J.A. Muñoz 《Corrosion Science》2006,48(10):3035-3048
The influence of silicon carbide particles (SiCp) proportion and matrix composition on aluminium metal matrix composites A3xx.x/SiCp modified by cerium-based conversion or electrolysis coating was evaluated in 3.5 wt.% NaCl at 22 °C using potentiodynamic polarization and gravimetric measurements. Ce-treated surfaces presented better corrosion behaviour in chloride media than original composite surfaces without treatment. Both treatments preferentially covered the intermetallic compounds and SiCp. The electrolysis afforded a higher degree of protection than conversion treatment because the coating was more extensive. Coating microstructure and nature of corrosion products were analysed by scanning electron and atomic force microscopy (SEM, AFM) and low angle X-ray diffraction (XRD). 相似文献
16.
A. Ostovari S.M. Hoseinieh M. Peikari S.R. Shadizadeh S.J. Hashemi 《Corrosion Science》2009,51(9):1935-1949
The inhibitive action of henna extract (Lawsonia inermis) and its main constituents (lawsone, gallic acid, α-d-Glucose and tannic acid) on corrosion of mild steel in 1 M HCl solution was investigated through electrochemical techniques and surface analysis (SEM/EDS). Polarization measurements indicate that all the examined compounds act as a mixed inhibitor and inhibition efficiency increases with inhibitor concentration. Maximum inhibition efficiency (92.06%) is obtained at 1.2 g/l henna extract. Inhibition efficiency increases in the order: lawsone > henna extract > gallic acid > α-d-Glucose > tannic acid. Also, inhibition mechanism and thermodynamic parameters are discussed. 相似文献
17.
Guozhe Meng Liyan Wei Tao Zhang Yawei Shao Fuhui Wang Chaofang Dong Xiaogang Li 《Corrosion Science》2009,51(9):2151-2157
A microcrystalline aluminium film with grain size of about 400 nm was prepared by magnetron sputtering technique. Its corrosion behaviour was investigated in NaCl containing acidic solution by means of potentiodynamic polarization curves and electrochemical noise (EN). The polarization results indicated that the corrosion potential of the sample shifted towards more positive direction, while its corrosion current density decreased compared with that of pure coarse-grain Al. The EN analysis based on stochastic model demonstrated that there existed two kinds of effect of microcrystallization on the pitting behaviour of pure aluminium: (1) the rate of pit initiation is accelerated, (2) the pit growth process was impeded. This leads to the enhancement of pitting resistance for the microcrystallized aluminium. 相似文献
18.
The present investigation was undertaken to analyze the effects of isothermal ageing treatments, carried out between 700 and 900 °C for a variety of times up to two weeks and followed by water quenching, on the microstructure and on the localized corrosion resistance of a superduplex stainless steel, SAF 2507.The quantitative metallography coupled with X-ray diffraction techniques was adopted to follow the microstructural evolution, together with SEM microscopy.Electrochemical potentiodynamic tests, as cyclic polarization curves recorded in sodium chloride solutions, together with weight loss measurements were employed to evaluate the susceptibility of the aged specimens to pitting corrosion.The influence of the transformation of ferrite into secondary austenite and sigma phase and of other microstructural variations, as chromium nitrides precipitation, on the stability of the passive film is shown. The susceptibility of the aged alloy to pitting corrosion phenomena, is related to sigma phase precipitation in association to the secondary austenite formation, which lead to a noticeable Cr depletion at grain boundaries. 相似文献
19.
The corrosion behaviour of AZ92 magnesium alloy reinforced with various volume fractions of silicon carbide particles (SiCp) and treated by alternating current (AC) plasma electrolytic oxidation (PEO) was investigated in humid and saline environments. For untreated composites, corrosion attack started around the Al-Mn inclusions and gradually developed into general corrosion without significant galvanic coupling between the matrix and the SiCp. PEO coatings consisted mainly of MgO and Mg2SiO4, and revealed increased hardness, reduced thickness and slightly higher corrosion resistance with increasing proportion of reinforcement. Pit formation and hydration of the outer layer were the main mechanisms of corrosion of PEO-treated specimens. 相似文献
20.
Corrosion of X65 steel in CO2-saturated oilfield formation water in the absence and presence of acetic acid 总被引:1,自引:0,他引:1
G.A. Zhang 《Corrosion Science》2009,51(8):1589-263
Electrochemical corrosion behavior of X65 steel in CO2-saturated formation water in the absence and presence of acetic acid was studied by electrochemical measurements, scanning vibrating micro-electrode (SVME), localized electrochemical impedance spectroscope (LEIS) and surface analysis techniques. It is found that, when steel is immersed in formation water, the dissolution of Fe dominates the anodic process and the steel is in active dissolution state. Adsorption of intermediate product on the electrode surface results in generation of an inductive loop in the low frequency range of EIS plot. As corrosion proceeds, the concentration of Fe2+ in the solution increases. When the product of [Fe2+] × [] exceeds solubility product of FeCO3, FeCO3 will deposit on the electrode surface, and protects the steel substrate from further corrosion. The steel is in a “passive” state. When the electrode surface is completely covered with FeCO3 film, the inductive loop in the low frequency range disappears. In the presence of acetic acid in formation water, the cathodic reaction will be enhanced due to the direct reduction of undissociated acetic acid. Addition of acetic acid degrades the protectiveness of corrosion scale, and thus, enhances corrosion of steel by decreasing the FeCO3 supersaturation in solution. 相似文献