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1.
Corrosion of Ni–Cr–Mo–V high strength steel at different hydrostatic pressures is investigated by scanning electron microscopy (SEM) and finite element analysis (FEA). The results indicate that corrosion pits of Ni–Cr–Mo–V high strength steel originate from inclusions in the steel and high hydrostatic pressures accelerate pit growth rate parallel to steel and the coalescence rate of neighbouring pits, which lead to the fast formation of uniform corrosion. Corrosion of Ni–Cr–Mo–V high strength steel under high hydrostatic pressure is the interaction result between electrochemical corrosion and elastic stress. 相似文献
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AC-induced corrosion is a controversial subject and many aspects of it need to be clarified, first and foremost, the mechanism and relationship between AC density and corrosion rate. This paper (Part 1) presents and discusses the effects of AC interference on kinetics parameters; the effects on corrosion rate and corrosion mechanism will be discussed in Part 2. Polarisation curves were obtained in different solutions (soil-simulating solution, 35 g L−1 NaCl, 1 M FeSO4, 1 M CuSO4 and 1 M ZnSO4) on different metallic materials (carbon steel, galvanised steel, zinc and copper) in the presence of AC interference (30-1000 A/m2). 相似文献
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Effect of hydrostatic pressure on the corrosion behaviour of Ni-Cr-Mo-V high strength steel was investigated by electrochemical measurements and SEM observation. The electrochemical noise (EN) data was analyzed based on non-linear dynamic theory. The experimental results revealed that hydrostatic pressure decreased the corrosion resistance of Ni-Cr-Mo-V steel and the corrosion at high hydrostatic pressure was more uniform due to the higher initiation rate and lower growth probability of metastable pitting. 相似文献
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Corrosion behavior of low-alloy steel containing 1% Cr (1Cr) with normalized (ferritic–pearlitic) and quenched-and-tempered (tempered martensitic) microstructures was investigated in CO2 environments at 60 °C. The severe localized corrosion which was observed in N80 carbon steel, did not exist for 1Cr steel due to the formation of a compact and self-repairable Cr-rich scale. For 1Cr steel, the corrosion resistance with ferritic–pearlitic microstructure was better than that with tempered martensitic microstructure. An apparent corrosion scale spallation was observed on the surface of quenched-and-tempered 1Cr steel, while only slight scale spallation was seen for normalized 1Cr steel. 相似文献
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To simulate the interaction between different coating holidays on buried pipeline under alternating current (AC) interference, laboratory experiments were carried out using a specially designed circuit connecting two specimens of different sizes. The application of AC between two different specimens could induce DC current from the smaller specimen to the bigger one in the solution, which would increase the corrosion rate of the smaller specimen. The research showed that size difference between holidays on buried pipeline is an important factor in accelerating AC corrosion. 相似文献
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The erosion resistance of CO2 corrosion scales formed on carbon steel was investigated in water–sand two-phase flow utilizing weight loss test, scanning electron microscopy, and X-ray diffraction. The effects of CO2 partial pressure, stirring speed, test time, and grain size on the erosion resistance of the scales were analysed. Results show that several characteristics of CO2 corrosion scales are key factors affecting erosion resistance. Cubic polynomials are used to fit the erosion rate data, and effectively evaluate the ability of CO2 corrosion scales to resist erosion. An erosion mechanism, based on fluid dynamics and CO2 corrosion scales characteristics, is discussed. 相似文献
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The corrosion inhibition of 2-hydrazino-4,7-dimethylbenzothiazole on low carbon steel in industrial water has been investigated at different temperatures and fluid velocities at different concentrations of the inhibitor using mass loss, potentiodynamic polarization and electrochemical impedance spectroscopy measurements. The results showed that corrosion resistance increased by increasing the inhibitor concentration. Optimization of the three variables has been made and correlating the results obtained using Box–Wilson statistical method. The adsorption process on low carbon steel surface obeys Flory–Huggins isotherm. The values of ΔGads obtained suggest that, the adsorption process of 2-HMBT on low carbon steel is chemisorption. The activation energy increased with increasing the concentration of inhibitors leading to decrease of the pre-exponential factor, and the entropy of activation increased negatively in the presence of inhibitor. SEM was used to identify the film formed on the metal surface. 相似文献
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Weathering steel corrosion was monitored for one to two years under natural atmosphere by an electrochemical impedance technique. Two identical comb-shape weathering steel sheets embedded in epoxy resin were used as monitoring probe electrodes at two different bridges in Japan. Impedances at 10 kHz (Z10kHz) and 10 mHz (Z10mHz) were automatically measured every hour. Coupons (50 × 50 × 2 mm3) prepared from the same steel sheets were exposed together to measure the corrosion mass loss. The average (Z10mHz)−1 value for half to one year exposure correlated well with the average corrosion rate determined from the corrosion mass loss. 相似文献
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Metallic substrates and rust layers of several hundred year old (y.o.) ferrous artefacts were characterised. Composition, structure and porosity of the rust were analysed by different methods: OM, SEM, EDS, EPMA, XRD, μXRD, SAXS, BET and mercury porosimetry.Several important parameters to describe an old rust layer were determined and measured. These parameters will be used for the modelling of long-term indoor atmospheric corrosion. 相似文献
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Changliang Hu Shuang Xia Hui Li Tingguang Liu Bangxin Zhou Wenjue Chen Ning Wang 《Corrosion Science》2011,(5):1880-1886
The grain boundary network (GBN) was controlled by grain boundary engineering (GBE) in a 304 stainless steel. The total length proportion of Σ3n coincidence site lattice (CSL) boundaries was increased to more than 70% associating with the formation of large size highly twinned grain-cluster microstructure. Only coherent twin boundaries (Σ3c) were found to be resistant to intergranular corrosion (IGC) and only such boundaries could be termed “special” ones. The improvement of resistance to IGC of the GBE specimen can be attributed to the large size grain-clusters associated with high proportion of the Σ3n boundaries and the interconnected Σ3n-type triple junctions. 相似文献
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This paper investigates the impact of additional nitrate sources on mild steel coupon corrosion in a seawater/sediment system. The results show that addition of 5 mM of nitrate sources significantly increased the weight loss of coupons after 20 weeks. SEM results indicate increase in microbial populations and corrosive products in the non-autoclaved and the nitrate-treated environments. EDX analyses revealed an increase in contents of carbon, calcium, magnesium, phosphorus and sodium with the exception of iron with an increase in incubation time. 相似文献
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Corrosion was studied in vitro in Nor’s solution (CO2 – bicarbonate buffered Hank’s solution) at 37 °C, and in vivo implanted in the lower back muscle of rats. Nor’s solution is a good model for HP Mg and WZ21, because (i) the pH is maintained by the same buffer as in blood and (ii) concentrations of corrosive chloride ions, and other inorganic constituents, are similar to those in blood. The higher in vitro corrosion rate of AZ91 was caused by micro-galvanic from second phases. The lower in vivo corrosion rate of AZ91 was tentatively attributed to suppression of micro-galvanic corrosion by tissue encapsulation. 相似文献
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The initial corrosion behavior of carbon steel subjected to outdoor wet-dry cyclic exposure and exposure under natural environments have been investigated. The weight loss results indicate a transition from corrosion acceleration to deceleration during the early stage of corrosion of carbon steel under both conditions. The corrosion kinetics under both conditions follow empirical equation D = Atn. Outdoor wet-dry cyclic exposure significantly promoted the initiation but the rate of corrosion was about three times as fast. The morphology of corrosion surfaces and cross-section of rust layer have been examined using SEM and the compositions have been analyzed using XRD and EPMA. 相似文献
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The high corrosion inhibition effectiveness of 2-mercaptobenzimidazole (MBIH) in 3 wt.% aqueous NaCl solution is reported using long term immersion tests, 3D-profilometry, electrochemical impedance spectroscopy, and potentiodynamic curve measurements. The high corrosion inhibition performance was proven after 180 days of immersion. The impedance spectra were characterized by two time constants relating to charge transfer and finite layer thickness or semi-infinite diffusion of copper ions through the surface layer, therefore Cu corrosion in solution containing MBIH follows kinetic-controlled and diffusion-controlled processes. Moreover, it is shown that MBIH is a mixed-type inhibitor. 相似文献
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With the use of sol–gel it is possible to apply zirconia coatings to reduce high temperature oxidation of steel. Some limitations of this technique are high hydrolysis rates and the formation of cracks during the drying stage. In this work, the mole ratio of zirconium butoxide to ethylacetate, and the nature of the catalyst were varied. SEM-EDX was used to evaluate the continuity of the zirconia coatings, and thermo-gravimetric analysis for the oxidation rate of coated samples. Thin and continuous coatings were obtained. With a basic catalyst, the coatings were crack-free and presented lower oxidation rate than acid-catalyzed coatings. 相似文献
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Sixteen custom binary Mg–Zr alloys and four commercial Zr-containing Mg-alloys were used to investigate the role of Zr on the corrosion of Mg. Mg–Zr alloys were manufactured with a range of different Zr concentrations. It was observed that the Mg–Zr alloys with a smaller mean Zr particle size had more Zr dissolved in solid solution. Both the Zr in solid solution and in metallic particle form were observed to have a deleterious effect on the corrosion rate of Mg. However, this deleterious effect is less pronounced to effect in alloys with multiple alloying additions. 相似文献
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Electrochemical techniques for determining corrosion rate of rusted steel in seawater 总被引:2,自引:0,他引:2
Corrosion rates of mild steel for long-term immersion were estimated by electrochemical and weight-loss methods. The results showed that application of electrochemical methods yielded erroneous values. The main reason was that, β-FeOOH, produced after long-term immersion with high electrochemical activity in the inner rust layer, exerted significant influence. In electrochemical tests, even small polarization can make β-FeOOH participate in cathodic reaction, which leads to overestimating corrosion rate. In order to confirm it, electrochemical behaviour was studied in aerated and deaerated conditions to investigate the effect of rust layers on reduction reaction. After calibration, the electrochemical measurement result was coincided with the weight loss. 相似文献
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2,2′ benzothiazolyl disulfide (BTDS) has been synthesised and their inhibiting action on mild steel corrosion in 1 M HCl and 0.5 M H2SO4 at 308 K has been investigated using weight loss, EIS, polarization and SEM study. BTDS showed better efficiency in 0.5 M H2SO4 compared to 1 M HCl. Polarization studies revealed that BTDS is a mixed type inhibitor in both acids predominantly cathodic in 1 M HCl where as predominantly anodic in 0.5 M H2SO4. Thermodynamic parameters i.e. free energy of adsorption, enthalpy, entropy and activation energy were calculated, the values of these parameters showed good interaction. 相似文献
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Iron corrosion under atmospheric conditions has been investigated by using the gold markers method. The corrosion experiments were performed in a climatic chamber with an accelerated treatment. The gold markers localization, carried out by scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, revealed that the rust layer growth was essentially due to an internal development. Moreover, microRaman mappings allowed prediction of the mechanism of rust layer evolution during the ageing treatment. Finally these results were compared to samples corroded for several 100 years in order to extrapolate our observations to long term corrosion. 相似文献