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The effect of the buffer capacity of test solution on the corrosion rate of cast pure (>99.95 mass%) and high-purity (>99.9999 mass%) magnesium, and AZ31 and AZ91E has been studied. Their corrosion rates were measured gravimetrically in a pH 6.5 and a pH 9 borate buffer including chloride ions, and in a conventional chloride solution. Except for the AZ91E in the pH 6.5, the corrosion rates of all the examined materials depended solely on the pH of the test solution, although the materials had a variety of purity and alloying elements. Higher buffer capacity probably masked the detrimental effect of the “cathodic impurities”. The corrosion rates measured in the buffers were considered as giving the resistivity of the passive film to anodic reactions. The high-purity magnesium had a fair corrosion resistance even in conventional chloride solution. 相似文献
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Corrosion behavior of equal-channel-angular-pressed pure magnesium in NaCl aqueous solution 总被引:1,自引:0,他引:1
Effect of microstructure change on corrosion behavior of equal-channel-angular-pressed (ECAPed) pure Mg was investigated. The ECAPed sample after 6 passes obtained finer grains (50-100 μm) compared with as-cast one (800-1500 μm). The strain-induced grain refinement with more crystalline defects weakened corrosion resistance of pure Mg, resulting in more and deeper pits after in-situ corrosion, higher mass-loss rate immersed in NaCl solution, larger Icorr values in polarization curves and lower fitted Rt values in EIS plots. However, the enhanced initial OCP values indicate better weather resistance. Furthermore, corrosion improvement can be expected by reducing defects via subsequent annealing. 相似文献
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Reidar Tunold Hans Holtan May-Britt Hägg Berge Axel Lasson Rolf Steen-Hansen 《Corrosion Science》1977,17(4):353-365
Measurements have been performed in order to relate different aspects of the corrosion of magnesium.Magnesium is shown to be a naturally passive metal that undergoes pitting corrosion when exposed to chloride ions in non-oxidizing solutions.By polarizing the metal in the negative direction an arrest on the current density/potential curve is found, probably corresponding to an activation potential. This potential determines the negative limit of the passive range.The “negative difference effect” is proposed to be a direct result of the breakdown of passivity. 相似文献
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1 INTRODUCTIONBecauseofitshighmechanicalperformanceandlowdensity ,LY12alloy(USAA2 0 2 4 )iswidelyusedintheaircraftindustryfornumerousapplicationssuchasfuselage ,doorskin ,dorsalfinandtrailingedgepanels .Nevertheless ,thisalloycaneasilybeaffectedbylocalizedcorrosion ,suchaspittingandexfoliation ,especiallyinchloridecontainingenvironment .Thislocalizedattackcanresultinprematurebreakdownofstructuralparts[1] .Inordertominimizethelocalizedattackonthealuminumalloy ,thecorrosionmecha nismshou… 相似文献
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The corrosion behavior of a resin-sealed flame-sprayed titanium coating in 3.5% NaCl solution was investigated by electrochemical
polarization measurements. The composition and structure of the sprayed film was also analyzed by scanning electron microscopy
(SEM) and electron probe x-ray microanalysis (EPMA). Although an as-sprayed titanium coating exhibited no resistance to corrosion
because of its porosity, the sprayed titanium sealed with epoxy or silicon resin showed an excellent resistivity with respect
to chloride corrosion. Although almost half of the titanium changed to oxides, nitrides, and carbides through the wire flame
spraying, the conversion of the metal to those compounds had little effect on decreasing the corrosion resistivity. The sprayed
and sealed titanium coating obtained by conventional on-site thermal spraying is expected to be an economical material for
chloride containing environments.
Presented at United Thermal Spray Conference & Exposition ’97, 15–18 September 1997, Indianapolis, IN. 相似文献
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Jianrui Liu Yina Guo Weidong Huang 《Protection of Metals and Physical Chemistry of Surfaces》2012,48(2):233-237
A chromium-free composite conversion treatment for magnesium by phytic acid and CeCl3 solutions was studied. The composite coatings on the surface of magnesium presented network-like cracks, which was consisted
of Mg, O, C, P and Ce elements. The distribution of Ce on the surface layer was non-uniform. The crack sizes of the composite
coating were smaller than that of the phytic acid conversion coating. The corrosion process of the coatings was evaluated
through electrochemical impedance spectroscopy in 3.5% NaCl solution, and the equivalent circuit of RL(Q(R(QR))) model was
obtained through the characteristics of EIS. The average corrosion rate of the composite coating was reduced at least 50%
compared with that of pure phytic acid conversion coating. 相似文献
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AZ series Mg alloys AZ31, AZ61, and AZ80 are widely applied in 3C (computer, communication, and consumer electronic) industry. Their corrosion characters in simulated sweat solution have been investigated by electrochemical technology, surface analysis, and pH measurements. Electrochemical test results showed that the three magnesium alloys revealed different corrosion resistance (Rt) in simulated sweat solution, Rt(AZ31) < Rt(AZ61) < Rt(AZ80). Three major components of simulated sweat solution played different roles during corrosion processes. Lactic acid was a kind of strong erosive medium for the magnesium alloys, and NaCl can induce pitting corrosion on alloys surface, while urea acted as a corrosion inhibitor. The corroded surface morphology of the three magnesium alloys was observed using scanning electron microscopy (SEM) and corrosion products were analyzed by X‐ray diffraction (XRD). Result of pH measurement tests showed that there were differences in climbing speed and final values of pH for the three magnesium alloys in simulated sweat solution. 相似文献
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Corrosion action and passive mechanism of magnesium alloy in the fluoride solution were studied by means of scanning electron microscopy(SEM), energy dispersive X-ray spectroscopy(EDS), and electrochemistry methods. The results show that an insoluble MgF2 film is generated on the surface of magnesium alloy activated in the hydrofluoric acid. And the mass of the deposited MgF2 film may reach a constant value, when the mass ratio of Mg/F on the magnesium alloy surface is fixed at 11.3-1. The activated magnesium alloy gains a 'passivation state' in a mixture of sulfuric acid and hydrofluoric acid at a volume ratio of less than 1.2. At the same time the mass of magnesium alloy is maintained as a function of the time. When the ratio is above 1.4, the mass of magnesium alloy rapidly decreases. The passive film formed through adsorption of HF2- (or H2F3-, H3F4-) ions by the deposited MgF2 film can protect the magnesium alloy from corrosion in fluoride solution, but not in non-fluoride solutions. The passive state is maintained for activated magnesium alloy in an acidic sulfuric nickel solution with added fluoride. If fluoride and carbonate are added to the acidic sulfuric nickel solution, a replacement reaction between magnesium alloy and solution takes place. 相似文献
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Corrosion behavior of WE54 magnesium alloy in 3.5%NaCl solution 总被引:1,自引:0,他引:1
The corrosion behavior of WE54 magnesium alloy was investigated in 3.5%NaCl aqueous solution. The electrochemical study shows that the value of corrosion potential of WE54 magnesium was -1.8V(vs SCE). In the initial stage of immersion, a kind of visible thin film, which has the appearance of artificial conversion coating by microscopy observation, formed on the surface of WE54 alloy. Through the comparison of corrosion behavior between WE54 and AZ91D, it is shown that the value of corrosion potential of WE54 is approximately 200 mV lower than that of AZ91D, and the corrosion rate of WE54 was one order smaller than that of AZ91D. After 72 h constant immersion and corrosion products removal, deeper grooves along grain boundaries was revealed but lighter corrosion was apparent on the matrix of WE54 alloy. As far as AZ91D alloy was concerned, severe localized corrosion was dominant and network-bone-like structure was remained. 相似文献
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Polymeric nano-film on the surface of Mg-Mn-Ce magnesium alloy was fabricated by polymer plating of 6-dihexylamino-1,3,5-triazine-2,4-dithiol monosodium(DHN) to improve its corrosion resistance.The electrochemical reaction process was analyzed by cyclic voltammetry and two obvious peaks of oxidation reaction were observed.The static contact angle of distilled water on polymer-plated surface can be up to 106.3°while on the blank surface it is 45.8°.Potentiodynamic polarization results show that the polyme... 相似文献
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The corrosion and electrochemical behavior of extruded AZ31D magnesium alloys in NaCl solution were investigated using SEM, XRD and electrochemical method. It is found that AZ31D is susceptive to Cl^- ion, and the open circuit potential shifts to more negative values with increasing chloride concentration. Pitting occurs at corrosion potential and corrosion area enlarges with enhanced polarization. Tafel slopes of the cathode branches in different testing solution are almost the same. Cl^- concentration affects cathode course slightly. High frequency capacitive loops shrink with the increase of Cl^- concentration. Corrosion initiates from the grain boundary and spreads to entire surface with time. 相似文献
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Manuele Dabalà Irene Calliari Alessandra Variola 《Journal of Materials Engineering and Performance》2004,13(2):237-240
Super duplex stainless steels (SDSS) have been widely used as structural materials for chemical plants (especially in those
engaged in phosphoric acid production), in the hydrometallurgy industries, and as materials for offshore applications due
to their excellent corrosion resistance in chloride environments, compared with other commercial types of ferritic stainless
steels. These alloys also possess superior weldability and better mechanical properties than austenitic stainless steels.
However, due to their two-phase structure, the nature of which is very dependent on their composition and thermal history,
the behavior of SDSS regarding localized corrosion appears difficult to predict, especially in chloride environments. To improve
their final properties, the effect of the partition of the alloying elements between the two phases, and the composition and
microstructure of each phase are the key to understanding the localized corrosion phenomena of SDSS. This paper concerns the
effects of the SDSS microstructure and heat treatment on the SDSS corrosion resistance in aqueous solutions, containing different
amounts of NaCl at room temperature. 相似文献
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J.B. Bajat I. Milošev R.M. Jan?i?-Heinemann V.B. Miškovi?-Stankovi? 《Corrosion Science》2010,52(3):1060-1069
The corrosion protection of vinyltriethoxysilane (VTES) films on aluminium during exposure to 3% NaCl was investigated using electrochemical impedance spectroscopy (EIS), potential-time measurements and optical microscopy coupled with image analysis. Composition and thickness of films were analyzed using Auger electron spectroscopy (AES) combined with depth profiling. It was shown that films deposited from 5% solution were significantly thicker and exhibited lower porosity and better corrosion stability, as compared to films deposited from 2 vol.% solution. VTES films deposited from 5 vol.% solutions and cured for 30 min exhibited better protection properties than other investigated films. 相似文献
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《Corrosion Science》2005,47(6):1534-1544
The inhibition of two terdentate ligands, 2-[(E)-pyridin-2-ylimino)methyl)]phenol and 2-[(pyridin-2-ylamino)methyl]phenol, abbreviated L1 and L2 respectively, on the corrosion of brass in 0.10 M NaCl solution under various conditions, has been studied by means of the potentiostatic polarization and AC impedance methods. The studies show that terdentate ligands, L1 and L2 inhibit the corrosion of brass in chloride solution and that the inhibiting efficiency increases with an increase in their concentrations. Self-assembled films of these substances were also prepared on the brass surface. These films improved significantly the protecting ability of brass surface to corrosion in 0.10 M NaCl solution. When the films were modified with benzotriazole (BTA), the quality and corrosion resistance of films improved markedly. 相似文献
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The corrosion behavior of as‐cast AZ91D magnesium alloy in 0.1M sodium sulfate solution at the corrosion potential (Ecorr) was investigated by using electrochemical impedance spectroscopy (EIS), environmental scanning electron microscopy (ESEM), energy dispersive X‐ray spectroscopy (EDS) and X‐ray diffraction (XRD). The results showed that the corrosion of AZ91D started at both the primary α‐Mg and the eutectic α‐Mg. The surface first was covered by a film (MgO, Mg(OH)2) which became thicker with time. Due to the dissolution of the eutectic α‐Mg, the concentration of aluminum increased, MgAl2(SO4)4 · 2H2O precipitated at the primary α‐Mg and progressively spread to the eutectic α‐Mg areas. The surface film changed from two‐layer to three‐layer structure with the increase of immersion time. 相似文献
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The corrosion mechanism of AZ31 magnesium alloy used as automobile components and the influence of the concentration of Cl- ion in simulated acid rain (SAR) were studied by electrochemical tests and SEM. The results show that pitting corrosion happens around the AlMn phases locating at the grain boundary. The corrosion of AZ31 magnesium alloy in SAR is controlled by the rate of anodic dissolution and hydrogen evolution, and the corrosion rate of AZ31 increases with increasing concentration of Cl- ion. However, the Cl- ion in SAR is not the main influencing factor inducing the pitting corrosion. 相似文献