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1.
Zn–Ni/Ni and Ni/Zn–Ni compositionally modulated multilayer (CMM) coatings were prepared by dual‐bath technique. The effects of layers number and sublayers order were studied. Specially, the effect of different sublayers thickness ratios with the same multilayer period (λ) on the corrosion resistance of the CMM coatings was investigated in detail. Results showed that the corrosion resistance of Ni/Zn–Ni (Zn–Ni alloy sublayer as the top layer) CMM coating was better than that of Zn–Ni/Ni (Ni sublayer as the top layer) CMM coating. The 6‐layer CMM coating with the layer thickness ratio of Ni/Zn–Ni = 0.8:1.2 (λ = 2 µm) has the best corrosion resistance. 相似文献
2.
Corrosion study of Ni/Zn compositionally modulated multilayer coatings using electrochemical impedance spectroscopy 总被引:1,自引:0,他引:1
Ni/Zn compositionally modulated multilayer (CMM) coatings were deposited using dual bath technique. Coatings corrosion performance was evaluated using electrochemical impedance spectroscopy (EIS) during extended immersion times up to 48 h. The results of electrochemical impedance spectroscopy showed that Ni/Zn CMM coatings had better corrosion resistance compared to that of the zinc single layer coating. The modified corrosion product which is formed on the Ni/Zn CMM coatings during extended exposure times and also a good barrier effect of the nickel layer against aggressive species in these coatings can be two important reasons for high corrosion performance and so protection performance of the Ni/Zn CMM coatings. 相似文献
3.
Z.I. Ortiz P. Díaz-Arista Y. Meas R. Ortega-Borges G. Trejo 《Corrosion Science》2009,51(11):2703-2715
The morphology, composition, phase composition and corrosion products of coatings of pure Zn (obtained from two types of electrolytic bath: an acidic bath (Znacid) and a cyanide-free alkaline bath (Znalkaline)) and of Zn–Mn and Zn–Co alloys on steel substrates were studied. To achieve this, diverse techniques were used, including polarization curves, atomic force microscopy (AFM), scanning electron microscopy (SEM), glow discharge spectroscopy (GDS), X-ray diffraction (XRD), and the salt spray test. In the salt spray test, the exposure time required for the coatings to exhibit red corrosion (associated with the oxidation of steel) decreased in the following order: Zn–Mn(432h) > Zn–Co(429h) > Znalkaline(298h) > Znacid(216h). The shorter exposure times required for corrosion of the pure Zn coatings are related to the coating composition and the crystallographic structure. Analysis of the corrosion products disclosed that Zn5(OH)8Cl2·H2O was a corrosion product of all of the coatings tested. However, the formation of oxides of manganese (MnO, Mn0.98O2, Mn5O8) in the Zn–Mn coating, and the formation of the hydroxide Zn2Co3(OH)10·2H2O in the Zn–Co coating, produced more compact and stable passive layers, with lower dissolution rates. 相似文献
4.
Zn? Ni/Ni? P compositionally modulated multilayer (CMM) coatings which have a novel three‐dimension (3d) latticed multilayer structure were prepared by dual‐bath technique. The formation of the special 3d latticed structure was investigated. The adhesion and corrosion resistance of the CMM coatings were studied. The results showed that the special 3d latticed multilayer structure, which was different from the structure of traditional CMM coatings, was formed during Ni? P electroless plating. The 3d latticed structure benefited the adhesion and corrosion resistance of the novel CMM coatings. The barrier effect of the 3d latticed structure is enhanced. 相似文献
5.
Cr-C coating was electrodeposited on copper and steel substrates, using a trivalent chromium bath containing formic acid. Coatings produced had an amorphous cracked structure with a homogeneous granular morphology. The coated copper specimen showed passivation behaviour, but, the coated steel specimens revealed an active anodic behaviour. Evaluation of coatings produced on the steel substrate subjected to various surface preparations including mechanically polished, electropolished and anodically etched, showed a crack-free coating on the preanodically etched surface. Also, this coating had the lowest porosity, which provided the best protection and thus led to the lowest dissolution of the steel substrate. 相似文献
6.
Zn–Ni–CNT composite coatings were prepared by electrodeposition from a sulphate bath. The effect of CNTs on the corrosion behavior, wear resistance and hardness of the composite coatings was investigated. Their corrosion properties were evaluated by polarization, impedance, weight loss and salt spray tests. The CNT particles inclusion improved the corrosion resistance, hardness and wear resistance of the coating. The grain size of the composite coating was smaller than that of a pure Zn–Ni coating with the same Zn/Ni ratio. Scanning electron microscope images and X-ray diffraction patterns of coating revealed its fine-grain nature. 相似文献
7.
The influence of drying temperature on the corrosion performance of chromate coatings on electro‐galvanized (EG) steel has been investigated using electrochemical impedance spectroscopy (EIS) and potentiodynamic measurements in 3.5% NaCl solutions. The chromate coatings were applied to the EG steel in a solution (pH 1.2) containing sodium dichromate and sulfuric acid at room temperature. The coatings were dried in an oven at three different temperatures: 60, 110 and 210°C. The surface of the chromate coatings was analyzed using atomic force microscopy (AFM) and scanning electron microscopy (SEM) combined with energy‐dispersive spectrometry (EDS). The results show that the drying temperature significantly affects the morphology of the chromate coatings and consequently affects their corrosion behavior. The chromate coatings dried at 110°C had few cracks and the lowest corrosion current. The chromate coatings dried at 60°C showed passivity. The EIS results show that the chromate coatings dried at 60°C has the largest impedance in a neutral 3.5% NaCl solution. Drying at higher temperature (210°C) degrades the chromate coatings by widening the cracks and reducing soluble Cr(VI) in the chromate layer. The favorable drying temperature for the chromate coatings on the EG steel is between 60 and 110°C. 相似文献
8.
《腐蚀工程科学与技术》2013,48(1):70-72
AbstractA photoelectrochemical investigation has been carried out on an ac modulated passive film on AISI 304 stainless steel in 0·1M Na2 B4O7 and 0·5M Na2 SO4 solutions. The results of the photocurrent measurements indicate that the photoresponse is determined by defects in the electronic structure of the films when the defects lead to localised states in the band gap region and that the photoresponse is sensitive to the passive condition and testing solutions. It is concluded that the passive film on 304 stainless steel is in a highly disordered amorphous state. 相似文献
9.
The influence of surface roughness on the performance of zinc-rich paint(ZRP) coatings was studied.Electrochemical impedance spectroscopy(EIS) measurements were used to assess the corrison prevention performance of the ZRP coatings.Furthermore,the EIS data of the steel-ZRP-sea water system were interpreted according to equivalent circuit models and the corresponding parameters were derived to assess the coating deterioration with time.The results show that the rougher surface favors better protection effect of the ZRP coatings.The protection potential of ZRP coatings for the standards and codes of practice is -0.78V(vs SCE). 相似文献
10.
S.T. Aruna C.N. Bindu V. Ezhil Selvi V.K. William Grips K.S. Rajam 《Surface & coatings technology》2006,200(24):6871-6880
Composite plating is a method of co-depositing fine particles of metallic or non-metallic compounds or polymers in the plated layer to improve material properties such as lubrication, wear resistance and corrosion resistance. In the present study, Ni was chosen as the matrix material and ceria nanoparticles were chosen as the distributed phase. Nanocrystalline ceria powder was synthesized by the solution combustion process and characterized by powder X-ray diffractometry (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The nanosize ceria particles were co-deposited with nickel from a nickel sulfamate bath using conventional electrodeposition method. The electrodeposition was carried out at current densities of 0.23, 0.77, 1.55, 3.1 and 5.4 A/dm2. The microhardness of the Ni matrix was enhanced by the incorporation of ceria particles. Potentiodynamic polarization, electrochemical impedance spectroscopy and SEM were used to characterize the corrosion behaviour of Ni and Ni/CeO2 coatings. These studies showed improved corrosion resistance for Ni/CeO2 when compared to Ni. The microhardness, corrosion resistance and wear resistance of Ni and Ni/CeO2 were compared. 相似文献
11.
Effects of Ti/TiN multilayer on corrosion resistance of nickel-titanium orthodontic brackets in artificial saliva 总被引:1,自引:0,他引:1
The effects of multilayered Ti/TiN or single-layered TiN films deposited by pulse-biased arc ion plating (PBAIP) on the corrosion behavior of NiTi orthodontic brackets in artificial saliva are investigated. The multilayered Ti/TiN coating is found to exhibit a greater free corrosion potential, much lower passive current density, and no breakdown up to 1.5 V. Moreover, electrochemical impedance spectroscopy (EIS) results indicate that the multilayered Ti/TiN coating has a larger impedance and lower porosity which is believed to be responsible for the exceedingly low metal ion release rate during 720 h exposure in the test solution. Visual inspection of the surfaces reveals different corrosion processes for the TiN and multilayered Ti/TiN coatings. 相似文献
12.
Nano CeO2 composite has been synthesized and explored as an effective activator for enhancing galvanic performance of hot-dip zinc coatings. The pre-treatment conditions and bath composition were optimized based on preliminary test results. Particle size of the CeO2 was characterized by XRD and TEM analyses. Various electrochemical techniques such as OCP decay measurements, Anodic polarization, Salt spray analysis and Electrochemical Impedance Spectroscopy (EIS) were adopted to evaluate galvanic performance of the CeO2-incorporated coatings. The coating incorporated with an optimum amount of CeO2, i.e. 0.1%, exhibited best galvanic performance. The incorporation of CeO2 caused significant improvement in galvanic and other physical characteristics of the coatings. It also resulted in lowering of the alloying reaction between zinc and iron, but enhanced barrier protection of the interior layers. 相似文献
13.
The quick-point grinding experiment of fluorophlogopite was conducted by using a MK9025A profile grinder which considered the simple single factor, such as the grinding wheel and table feed speed, grinding depth, inclining angle and deflection angle. The experimental results indicated that the surface roughness was mainly influenced on inclining angle and deflecting angle. Moreover, the modified model of the quick-point grinding process was proposed in the paper, which based on Malkin kinematics model, Snoeys empirical model and grinding thickness empirical model. The inclining angle and deflecting angle was introduced in the modified model. Comparison of the predicted results of these models and experimental ones indicated that the modified model was in well agreement with the experimental data. Further, standard deviation of these models and experiment was studied in the paper, it is found that the modified model was the more ideal. In order to study the effect of various technology factors on the sensitivity of surface roughness, “Relative extremum error” concept was first proposed in the paper. It was found that simple single factor in the modified model were relatively sensitive to surface roughness than other models. 相似文献
14.
Panels coated by hot dipping with zinc (HDG), Zn–5Al (Galfan) and Zn–1.5Al–1.5Mg coatings at different thicknesses were phosphated and painted on an industrial line. Crevice panels with non‐painted bare parts modelling conditions in hem flanges, reference panels with open surfaces and formed non‐painted panels were exposed to a cyclic accelerated automotive test. Zn–Al–Mg coatings with the thickness of 10 µm provided similar or even better protection than HDG and Galfan at 20 µm in both confined and open configurations. In comparison to 10‐µm HDG, the Zn–Al–Mg coating delayed red rust appearance in crevices by a factor of 2 and the maximal depth of corrosion in the steel substrate was by 42% lower. Confined areas were more corroded than open surfaces. For HDG, the time to red rust appearance dropped by 50–75%, corrosion attack in steel was from 3.5 to 7 times deeper and mass gain was about 2.3 times higher in crevices than on open surfaces. Corrosion of Zn–Al–Mg may be more affected by local environmental conditions created by the crevice configuration than for HDG. Red rust appearance on formed panels of 20‐µm Galfan, 7‐, 10‐ and 14‐µm Zn–Al–Mg was delayed to 10‐µm HDG by a factor of 2.8, 3.5, 3.8 and >4.5, respectively. No adverse effect of forming was noticed. The results indicate that 2‐ to 3‐fold reduction of the coating thickness for Zn–Al–Mg alloy coatings in comparison to traditional HDG may be possible without compromising the corrosion performance. 相似文献
15.
Rongchang Zeng Zidong LanLinghong Kong Yuanding HuangHongzhi Cui 《Surface & coatings technology》2011,205(11):3347-3355
Two kinds of phosphate conversion coatings, including zinc phosphate coating and zinc-calcium phosphate coating, were prepared on the surface of AZ31 alloy in phosphate baths. The morphologies of these coatings were observed using scanning electron microscopy. Their chemical compositions and structures were characterized using energy-dispersive X-ray spectrum, X-ray photoelectron spectroscopy and X-ray diffraction. The corrosion resistance of the coatings was evaluated by potentiodynamic polarization technique. The results show that the flowerlike Zn-Ca phosphate conversion coatings are mainly composed of hopeite (Zn3(PO4)2·4H2O). They have a quite different morphology from the dry-riverbed-like Zn phosphate coatings that consist of MgO, MgF2, Zn or ZnO and hopeite. Both of the zinc and zinc-calcium phosphate coatings can remarkably reduce the corrosion current density of the substrates. The Zn-Ca coating exhibits better corrosion resistance than the Zn coating. Introduction of calcium into the phosphate baths leads to the full crystallinity of the Zn-Ca coating. 相似文献
16.
Rossana GaziaPietro Mandracci Federico MussanoStefano Carossa 《Surface & coatings technology》2011,206(6):1109-1115
Aluminium nitride thin films were deposited on titanium fixtures, while silicon oxide thin films were deposited on titanium fixtures and chromium-cobalt substrates, using the RF magnetron sputtering technique. Each coating showed different corrosion behaviours when electrochemical characterisations were made in a simulated biological environment, i.e. Hank's solution. Although aluminium nitride was more effective in reducing the localised corrosion on titanium implants, silicon oxide showed the best behaviour against general corrosion and results were consistent for the two kinds of substrates. Moreover the application of a SiO2/AlN bilayer onto the Ti fixtures improved the performances of each separate coating. When the coated surfaces were compared to uncoated substrates, there was no statistically significant difference in cell viability in the response of two different human osteoblastic cell lines — Saos-2 and MG-63. Field emission scanning electron microscopy assessed the surface morphology of coated and uncoated samples, whilst Fourier transform infrared spectroscopy was applied to investigate the bonding structure of barrier layers on silicon samples. On the basis of the data obtained, we are of the opinion that the tested materials show some promising characteristics for the fabrication of novel dental implants with reduced ion release properties. 相似文献
17.
Mieczysaw Korzynski 《International Journal of Machine Tools and Manufacture》2007,47(12-13):1956-1964
The effect of a smoothing-burnishing process strongly depends on the initial roughness of a workpiece. This factor has not been considered by existing classical models of the processes. In this paper, assuming a model of burnishing with a spherical tool, in the form of wedges of surface roughness deformed with a force normal to the base line, expressions describing the relation between burnishing force and displacement of the tops of surface asperities is derived. The expression includes the effect of mechanical properties of the workpiece material, geometry of contact of the tool with the workpiece and the roughness of the burnished surface. Using the derived expressions it is possible to determine an optimum burnishing force. This has been verified experimentally. The experiment made it possible to demonstrate that the optimum burnishing force of the ground 42CrMo4 steel samples was 11–15 daN and that the burnishing effect depends a lot not only on the mechanical properties of the machined workpiece and the geometry of the contact area between the tool and the workpiece but also on the initial surface roughness. The applied optimum burnishing force, calculated on the basis of the theoretical, assumed model-derived dependences, is 12–13 daN. The above proves the validity of the adopted assumptions and the formulas worked out. 相似文献
18.
The study investigated the feasibility of modifying the surface of Al–Zn–Mg alloy by a combined process of electric discharge machining (EDM) with ball burnish machining (BBM). A novel process that integrates EDM and BBM is also developed to conduct experiments on an electric discharge machine. Machining parameters of the combined process, including machining polarity, peak current, power supply voltage, and the protruding of ZrO2, are chosen to determine their effects on material removal rate, surface roughness and the improvement ratio of surface roughness. In addition, the extent to which the combined process affects surface modification is also evaluated by microhardness and corrosion resistance tests. Experimental results indicate that the combined process of EDM with BBM can effectively improve the surface roughness to obtain a fine-finishing and flat surface. The micropores and cracks caused from EDM are eliminated during the process as well. Furthermore, such a process can reinforce and increase the corrosion resistance of the machined surface after machining. 相似文献
19.
Electrodeposition of Zn–Ni coatings performed in acidic baths are not suitable for high strength steels due to their high susceptibility to hydrogen embrittlement.In this work, Zn–Ni coatings were deposited on a high strength steel (4340) upon stirring conditions from an alkaline bath. A complete characterisation of the coatings (corrosion, morphology and composition) has been accomplished, correlating the electrodeposition conditions with these features. The best protective properties of the grown coatings were achieved for the alloys with a single phase structure of γ-Ni5Zn21 and a denser morphology. Additionally, the hydrogen content incorporated is lower than even cadmium-coated 4340 steel which has undergone a postbaking dehydrogenation treatment. 相似文献