Co-reporter:Yuchao Dun, Yu Zuo
Applied Surface Science 2017 Volume 416(Volume 416) pp:
Publication Date(Web):15 September 2017
DOI:10.1016/j.apsusc.2017.04.116
•A KH560/graphene coating was prepared on 2024 aluminum alloy by immersing and curing.•The thickness of the composite coating increased greatly compared with silane coating.•The covalent metallic-siloxane bonds improved the adhesion force greatly.•The laminate structure increased the hardness and declined brittleness of the coating.•The composite coating showed much higher corrosion resistance in NaCl solution.A γ-(2,3-epoxypropoxy) propyltrimethoxysilane/graphene (GPTMS/rGO) coating on AA-2024 aluminum alloy was prepared by immersing the aluminum alloy sample in a silane/graphene oxide solution and curing in oven at 180 °C. Silanol groups were grafted onto graphene oxide sheets during hydrolysis. The graphene oxide was stacked layer by layer through silanol groups. The synthesized coating was characterized with Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, Raman spectra and scanning electron microscopy. The thickness of the composite coating increased greatly compared with that of silane coating, due to the mutual riveting effect. The covalent metallic-siloxane bonds (AlOSi) improved the adhesion force greatly. The laminate structure of graphene increased the hardness and declined the brittleness over 200 °C. The GPTMS/rGO coating showed good corrosion resistance. In 3.5% NaCl solution the anodic current density of the aluminum alloy sample with GPTMS/rGO coating was reduced by several orders of magnitude compared with those of bare aluminum alloy or the sample with graphene film.
Co-reporter:Yu Zuo, Sirui Li, Xuhui Zhao, Yuming Tang
Surface and Coatings Technology 2017 Volume 330(Volume 330) pp:
Publication Date(Web):1 December 2017
DOI:10.1016/j.surfcoat.2017.09.064
•Pd-Co gradient coating is prepared on stainless steel by electrodeposition.•Gradient coating is obtained simply by changing plating current in the same bath.•From inner to outside, Co content in coating increases from 24 at.% to 36 at.%.•The coating shows high hardness and adherence, low internal stress and porosity.•The erosion-corrosion resistance of the gradient coating increases obviously.A Pd-Co gradient coating is prepared on stainless steel by simply controlling the electro-deposition current density in the same electrolyte bath. SEM, EDX, XRD, weight loss test and some other methods were used to determine the properties of the Pd-Co gradient coating. The result shows that Co content in the coating increases from about 24 at.% at the substrate/coating interface to about 36 at.% at the outside surface by changing the deposition current density. The coating is uniform, compact and the grain size decreases from the inner interface to the outside surface. Compared with coatings deposited at constant current densities, the Pd-Co gradient coating shows relatively higher micro-hardness, higher adherence strength to the substrate, lower internal stress and lower porosity. As the result, in stirred boiling acetic acid (90 wt%) and formic acid (10 wt%) mixtures containing 0.005 M Br− and solid particles, the gradient coating coated stainless steel samples show quite good erosion-corrosion resistance.
Co-reporter:Yishan Wang, Yu Zuo
Corrosion Science 2017 Volume 118(Volume 118) pp:
Publication Date(Web):1 April 2017
DOI:10.1016/j.corsci.2017.01.008
•Calcium lignosulfonate shows quite good inhibition for steel in concrete pore solution.•Inhibition efficiency is over 93% even after 7200 h immersion test.•Characteristic adsorption of calcium lignosulfonate on steel surface is observed.•Sinapyl alcohol in CLS molecule is the preferred active site for accepting electrons.The inhibition behavior of calcium lignosulfonate and sodium oleate for carbon steel in simulated concrete pore solution was studied. Calcium lignosulfonate showed good inhibition for steel in simulated concrete pore solution even after 7200 h immersion. The molecular simulation indicated that sinapyl alcohol in calcium lignosulfonate is the preferred site for accepting electrons. The microscopic infrared imaging showed that at the early stage of immersion the characteristic adsorption happened for calcium lignosulfonate at the corroded areas on the surface, which would be helpful for preventing initiation and propagation of both general and pitting corrosion.
Co-reporter:Yu Zuo, Li Yang, Yongjun Tan, Yishan Wang, Jingmao Zhao
Corrosion Science 2017 Volume 120(Volume 120) pp:
Publication Date(Web):15 May 2017
DOI:10.1016/j.corsci.2016.12.015
•In acidic NaCl + NaNO2 solution, addition of TAI promotes both passivation and pitting of X70 steel.•The decreased pitting resistance is attributed to preferential adsorption of residue TU monomers.•With extended immersion time, the pitting resistance increases to the original value without TAI.•A multi-layer film with thiourea rich in inner and imidazoline rich in outer formed on surface.•Inhibition effects of NaNO2 and TAI on steel are both superimposed and interactive.The effects of thioureido imidazoline and NaNO2 on passivation and pitting corrosion of X70 steel in acidic NaCl solution were studied. The addition of thioureido imidazoline promoted passivation of the steel in the NaCl-NaNO2 solution, but the pitting potential decreased, which was attributed to the preferential adsorption of residue thiourea monomers in the inhibitor. With longer immersion time, the pitting potential in solution with thioureido imidazoline + NaNO2 increased to the value with only NaNO2. A multi-layer film formed with thiourea rich in inner and imidazoline rich in outer. The compounded inhibition effect of thioureido imidazoline and NaNO2 was discussed.
Co-reporter:Hui-zhong ZHANG, Yang LI, Yu ZUO, Xu-hui ZHAO, Yu-ming TANG
Transactions of Nonferrous Metals Society of China 2017 Volume 27, Issue 7(Volume 27, Issue 7) pp:
Publication Date(Web):1 July 2017
DOI:10.1016/S1003-6326(17)60175-4
Pd–Ni coating shows good corrosion resistance in strong corrosion environments. However, in complex aggressive environments, the performance of the coatings is limited and further improvement is necessary. The effects of the applied plating current density on the composition, structure and properties of Pd–Ni coatings were studied. By changing the current density in the same bath, multi-layer Pd–Ni coatings were prepared on 316L stainless steel. Scanning electronic microscopy, weight loss tests, adhesion strength, porosity and electrochemical methods were used to study the corrosion resistance of the films prepared by different coating methods. Compared with the single layer Pd–Ni coating, the multi-layer coatings showed higher microhardness, lower internal stress, lower porosity and higher adhesive strength. The multi-layer Pd–Ni coating showed obviously better corrosion resistance in hot sulfuric acid solution containing Cl−.
Co-reporter:Yishan Wang, Yu Zuo, Xuhui Zhao, Shanshan Zha
Applied Surface Science 2016 Volume 379() pp:98-110
Publication Date(Web):30 August 2016
DOI:10.1016/j.apsusc.2016.04.013
Highlights
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Calcium lignosulfonate is effective inhibitor for steel in simulated pore solution.
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Both general corrosion and pitting can be inhibited by CLS.
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The preferential adsorption of CLS around pits was detected by M-IR.
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At beginning CLS adsorbs on surface unevenly and preferentially at active sites.
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After pre-filming time an intact adsorption CLS film forms on steel surface.
Co-reporter:Si-rui LI, Yu ZUO
Transactions of Nonferrous Metals Society of China 2016 Volume 26(Issue 1) pp:167-174
Publication Date(Web):January 2016
DOI:10.1016/S1003-6326(16)64103-1
Pd–Co films with the Co content varying from 21.9% to 34.62% (mole fraction) and Pd–Cu (5% Cu, mole fraction) film were electrodeposited on 316L stainless steel, and the erosion-corrosion resistance of the Pd–Co and Pd–Cu plated samples in a simulated boiling pure terephthalic acid (PTA) slurry environment was studied with methods of mass loss test, polarization measurement and scanning electron microscopy (SEM). Under the static state condition, both the Pd–Cu and Pd–Co plated samples exhibit good corrosion resistance and the Pd–Cu film behaves slightly better. However, with increasing the stirring speed, the corrosion rate of the Pd–Cu plated samples increases obviously while that of the Pd–Co plated samples shows only slight increase. Higher microhardness and lower surface roughness of Pd–Co film than those of Pd–Cu film, as well as good corrosion resistance, may be the main reasons for better erosion-corrosion resistance in the strong reductive acid plus erosion environment.
Co-reporter:Yong Zhou, Yu Zuo
Electrochimica Acta 2015 Volume 154() pp:157-165
Publication Date(Web):1 February 2015
DOI:10.1016/j.electacta.2014.12.053
Intergranular corrosion (IGC) is observed on mild steel surface when the steel is polarized to passive potential zone in CO2 + NaNO2 solution. The methods of potentiodynamic polarization, scanning electron microscope (SEM) and scanning tunneling microscope (STM) are applied to study the phenomenon. Intergranular corrosion mainly happens as the steel is polarized into the active–passive transition zone, and the width and depth of the corroded grain boundaries increase with potential in the zone. When the potential enters the passive zone, the depth of IGC shows only very slight change. The IGC is related to the segregation of the impurity elements Mn and Si at the grain boundaries. The occurrence of intergranular corrosion is influenced by the potential scanning rate and CO2 concentration in the solution. When the potential scanning rate is below 0.3 mV s−1 IGC phenomenon is observed. In saturated CO2 + NaNO2 solution no IGC is observed which may be attributed to the formation of FeCO3 layer on steel surface that protects the grain boundaries from corrosion. The observed IGC is due to the combined effect of CO2 and NaNO2 in solution. NO2− promotes passivation on the grain surface but CO2 induces corrosion at the grain boundaries.
Co-reporter:Biner Zhou, Yishan Wang, Yu Zuo
Applied Surface Science 2015 Volume 357(Part A) pp:735-744
Publication Date(Web):1 December 2015
DOI:10.1016/j.apsusc.2015.09.093
Highlights
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Inhibition effect of LaCl3 and SDBS for AA 2024 in NaCl solution (pH 10) was studied.
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At the beginning the active polarization behavior of the alloy changed to passivation.
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The passive behavior gradually disappeared with time and pitting happened at S-phases.
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The compounded inhibitors showed good inhibition but cannot totally inhibit pitting.
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The adsorption of SDBS played the key role for inhibition to the corrosion process.
Co-reporter:Sirui Li, Yu Zuo, Pengfei Ju
Applied Surface Science 2015 Volume 331() pp:200-209
Publication Date(Web):15 March 2015
DOI:10.1016/j.apsusc.2015.01.087
Highlights
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A Pd–Co alloy film is deposited on 316L stainless steel by electroplating.
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In hot, stirred acid solution with SiO2, Pd-Co film shows good erosion–corrosion resistance.
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There is a significant synergistic effect between erosion and corrosion for the tested system.
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At higher stirring speed the erosion effect plays key role in erosion–corrosion process.
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The good erosion–corrosion resistance of Pd-Co film is due mainly to its high hardness.
Co-reporter:Pengfei Ju, Yu Zuo, Junlei Tang, Yuming Tang, Zhongzhi Han
Materials Chemistry and Physics 2014 Volume 144(Issue 3) pp:263-271
Publication Date(Web):15 April 2014
DOI:10.1016/j.matchemphys.2013.12.024
•A Pd–Ni/Pd–Cu double coating is deposited on 316L stainless steel by electroplating.•The double coating increases the hardness and improves the adhesion to the substrate.•The coating shows good corrosion resistance in boiling acetic/formic acids mixture.•The effects of the double coating on corrosion and erosion resistance are discussed.A Pd–Ni/Pd–Cu double coating was deposited on stainless steel surface by electroplating. The microstructure and corrosion resistance of the double coating in strong reducing corrosive media were studied. In boiling 90 wt% acetic acid +10 wt% formic acid mixture containing 0.005 mol L−1 NaCl with 900 r min−1 stir, the corrosion rate of the double coating coated 316L stainless steel is one order of magnitude lower than that of Pd–Cu coated samples. The double coating shows lower porosity, higher hardness and elasticity modulus as well as higher adhesive strength, which may explain the better corrosion resistance in the testing environments.
Co-reporter:Yuming Tang 唐聿明;Xuhui Zhao;Le Niu
Journal of Wuhan University of Technology-Mater. Sci. Ed. 2014 Volume 29( Issue 2) pp:278-283
Publication Date(Web):2014 April
DOI:10.1007/s11595-014-0908-5
The adsorbing effect of calcined layered double hydroxide (CLDH) for chloride ions in simulated concrete pore (SCP) solutions was investigated with the potentiodynamic polarization method, impedance measurement, ion selective electrode analysis and XRD. CLDH could effectively adsorb Cl− and increase pH value in SCP solutions containing NaCl. The chloride to hydroxyl ions ratio ([Cl−]/[OH−]) of the solution greatly decreased by CLDH treatment. In CLDH treated SCP solution with Cl−, the pitting potential of carbon steel notably increased, and the surface impedance was much higher, indicating strengthened passivation. The process of CLDH adsorbing chloride ions from SCP solutions was accompanied with the reconstruction of the layered structure.
Co-reporter:Xiangyu Lu, Yu Zuo, Xuhui Zhao, Yuming Tang
Electrochimica Acta 2013 Volume 93() pp:53-64
Publication Date(Web):30 March 2013
DOI:10.1016/j.electacta.2013.01.078
The protective performance of a Mg-rich primer on AZ91D magnesium alloy was greatly improved by addition of aluminum tri-polyphosphate (SAP) pigment into the primer. The effects of SAP in the Mg-rich primer were investigated. In the first stage, the pigment SAP prolongs the cathodic protection of the Mg-rich primer for AZ91D alloy by a pH buffering effect. Then, the corrosion products of the magnesium particles, composed of phosphates and oxides of magnesium, form in the primer, which enhances the barrier effect of the primer. Finally, a protective layer composed of magnesium phosphates and oxides forms on the substrate surface.Highlights► Aluminum tri-polyphosphate (SAP) pigment is added in a Mg-rich epoxy coating. ► SAP improves anticorrosive performance of the Mg-rich coating on AZ91D alloy greatly. ► SAP prolongs cathodic protection of Mg-rich coating by a pH buffering effect. ► The formed phosphates and oxides of Mg strengthen the barrier effect.
Co-reporter:Xuhui Zhao 赵旭辉;Hao Ye;Xiaofeng Zhang
Journal of Wuhan University of Technology-Mater. Sci. Ed. 2012 Volume 27( Issue 2) pp:242-246
Publication Date(Web):2012/04/01
DOI:10.1007/s11595-012-0445-z
Ni element was introduced to aluminum surface by a simple chemical immersion method, and Al-Ni composite anodic films were obtained by following anodizing. The morphology, structure and composition of the Al-Ni anodic films were examined by scanning electron microscopy (SEM), energy disperse spectroscopy (EDS) and atomic force microscopy(AFM). The electrochemical behaviors of the films were studied by means of polarization measurement and electrochemical impedance spectroscopy (EIS). The experimental results show that the Al-Ni composite anodic film is more compact with smaller pore diameters than that of the Al anodic film. The introduction of nickel increases the impedances of both the barrier layer and the porous layer of the anodic films. In NaCl solutions, the Al-Ni composite anodic films show higher impedance values and better corrosion resistance.
Co-reporter:Zhongzhi Han, Yu Zuo, Pengfei Ju, Yuming Tang, Xuhui Zhao, Junlei Tang
Surface and Coatings Technology 2012 206(14) pp: 3264-3269
Publication Date(Web):
DOI:10.1016/j.surfcoat.2012.01.027
Co-reporter:Xingguo Feng, Yu Zuo, Yuming Tang, Xuhui Zhao, Xiangyu Lu
Electrochimica Acta 2011 Volume 58() pp:258-263
Publication Date(Web):30 December 2011
DOI:10.1016/j.electacta.2011.09.035
The degradation of passive film on carbon steel in concrete pore solution under tensile and compressive stresses is studied using electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) techniques. As the applied stress increases, the corrosion potential and impedance of the samples decrease. When the same stress magnitude is applied, under compressive stress the samples show more negative corrosion potentials and lower impedance values than those subjected to tensile stress. Two different modes for the failure of the passive film are proposed: tensile stress creates micro-cracks perpendicular to the surface, while compressive stress induces de-bonding of the interface between the passive film and the substrate. Thus, compressive stress produces more severe degradation of the passive film than does the tensile stress.Highlights► The degradation of passive film on carbon steel in concrete pore solution under stress is studied. ► As the applied stress increases, corrosion potential and impedance of the sample decrease. ► For the same stress magnitude, compress stress resulted in more severe damages in the passive film. ► Tensile stress mainly leads to micro-cracks perpendicular to the surface. ► Compress stress induces de-bonding of the interface between film/substrate.
Co-reporter:Junlei Tang, Zhongzhi Han, Yu Zuo, Yuming Tang
Applied Surface Science 2011 Volume 257(Issue 7) pp:2806-2812
Publication Date(Web):15 January 2011
DOI:10.1016/j.apsusc.2010.10.065
Abstract
Cerium oxide based coatings were prepared on AA2024 Al alloy by brush plating. The characteristic of this technology is that hydrogen peroxide, which usually causes the plating solution to be unstable, is not necessary in the plating electrolyte. The coating showed laminated structures and good adhesive strength with the substrate. X-ray diffraction and X-ray photoelectron spectroscopy analysis showed that the coatings were composed of Ce(III) and Ce(IV) oxides. The brush plated coatings on Al alloys improved corrosion resistance. The influence of plating parameters on structure and corrosion resistance of the cerium oxide based coating was studied.
Co-reporter:Yanfang Zhu, Jinping Xiong, Yuming Tang, Yu Zuo
Progress in Organic Coatings 2010 Volume 69(Issue 1) pp:7-11
Publication Date(Web):September 2010
DOI:10.1016/j.porgcoat.2010.04.017
The performance of acrylic polyurethane composite coating and aliphatic urethane composite coating in 3.5% NaCl solution under ultra-violet radiation was studied with methods of EIS, SEM and FTIR. For aliphatic polyurethane coating, the coating resistance decreased and the coating capacitance and porosity increased more quickly than acrylic polyurethane coating. The acrylic polyurethane composite coatings showed better performance than aliphatic polyurethane composite coatings. IR spectra showed that under UV irradiation conditions, the failure mechanism of the two polyurethane coatings was the transformation of sec-amide to primary amides. The fractured bonds in acrylic polyurethane were mainly C–O bonds, while in aliphatic polyurethane they were mainly C–N bonds. The lower protection property of aliphatic polyurethane coating may be mainly attributed to the C–N bonds which are more liable to be broken.
Co-reporter:Yuming Tang, Xuhui Zhao, Kuisheng Jiang, Jun Chen, Yu Zuo
Surface and Coatings Technology 2010 205(6) pp: 1789-1792
Publication Date(Web):
DOI:10.1016/j.surfcoat.2010.05.016
Co-reporter:Junlei Tang, Yu Zuo, Yuming Tang, Jinping Xiong
Surface and Coatings Technology 2010 204(9–10) pp: 1637-1645
Publication Date(Web):
DOI:10.1016/j.surfcoat.2009.10.048
Co-reporter:Qizheng Li, Yuming Tang, Yu Zuo
Materials Chemistry and Physics 2010 120(2–3) pp: 676-681
Publication Date(Web):
DOI:10.1016/j.matchemphys.2009.12.025
Co-reporter:Chengzhong Wang
Journal of Applied Polymer Science 2009 Volume 114( Issue 4) pp:2528-2532
Publication Date(Web):
DOI:10.1002/app.30803
Abstract
Laurylfluoro glycidyl ether (FGE) was synthesized by laurylfluoro-1-pentanol with epichlorohydrin, and confirmed by FTIR and 13C-NMR. The surface properties, moisture absorption, and mechanical properties of the epoxy resins modified by different content of laurylfluoro glycidyl ether acted as mono functional thinner were investigated by X-ray photoelectron spectroscopy (XPS), universal testing machine (UTM), dynamic mechanical thermal analyzer (DMTA), etc. The fluorine content at the surface of the modified resins were enriched greatly with the increase of the content of laurylfluoro glycidyl ether, and the hydrophobic property of the resins surface increased. When the FGE content was 10%, the fluorine content at the surface of the modified epoxy resin reached to 66% and the water contact angle was 102°. The equilibrium moisture content of the resin dropped by 30% when the content of FGE was 5%. The mechanical properties of the epoxy resins modified by FGE were improved while the thermal mechanical properties changed little at low content of FGE (less than 3%). Further increase of FGE content in the epoxy resins may result in decreases of the mechanical and thermal mechanical properties of the resins. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Co-reporter:Yuming Tang, Xuhui Zhao, Jianpeng Mao, Yu Zuo
Materials Chemistry and Physics 2009 Volume 116(2–3) pp:484-488
Publication Date(Web):15 August 2009
DOI:10.1016/j.matchemphys.2009.04.019
Metastable pitting and stable pitting behaviors of two carbon steels in 0.05 M Na3PO4 + 0.03 M Na2B4O7 + 0.03 M Na2SO4 solution with 0.05 M NaCl or without NaCl (pH = 9.4) were studied by polarization measurements, current fluctuation measurements, EIS tests and analysis of Mott–Schottky plots. Compared with A3 steel, 16Mn steel shows higher passive film impedance and lower pitting susceptibility, which is characterized by higher pitting breakdown potential Eb, metastable pitting potential Em and flat band potential Ufb values, and lower electron concentration in the passive film. When the potential is above Em, diffusion tails occur on the resistance plots, indicating the beginning of local damage to the surface.
Co-reporter:Weihua Liu, Yu Zuo, Shengli Chen, Xuhui Zhao, Jingmao Zhao
Surface and Coatings Technology 2009 203(9) pp: 1244-1251
Publication Date(Web):
DOI:10.1016/j.surfcoat.2008.10.032
Co-reporter:Yu Zuo, Junlei Tang, Chongzhi Fan, Yuming Tang, Jinping Xiong
Thin Solid Films 2008 Volume 516(Issue 21) pp:7565-7570
Publication Date(Web):1 September 2008
DOI:10.1016/j.tsf.2008.04.049
An uniform palladium film on 304 stainless steel was obtained by electroless plating. Scanning electronic microscopy, X-ray photoelectron spectroscopy, weight loss tests and electrochemical measurements were used to character the properties of the film. The palladium plated stainless steel samples showed excellent corrosion resistance in strong reductive corrosion mediums. In boiling dilute sulfuric acid solutions and boiling acetic/formic acids, corrosion rates of palladium plated 304 stainless steel samples were 3 or 4 orders of magnitude lower than the original 304 stainless steel samples. In solutions with NaCl concentration less that 0.1%, the palladium plated samples also showed better corrosion resistance. The function of palladium film on stainless steel is to raise the electrode potential and promote passivation of the steel in strong corrosive environments.
Co-reporter:Lian-Peng Tian, Xu-Hui Zhao, Yu Zuo, Jing-Mao Zhao, Jin-Ping Xiong
Materials Chemistry and Physics 2007 Volume 104(Issue 1) pp:24-29
Publication Date(Web):15 July 2007
DOI:10.1016/j.matchemphys.2007.02.084
The motivation of this study is to investigate the possibility of improving corrosion resistance of anodic films on aluminum by Ni ions implantation. The implantation of Ni ions was carried out using a MEVVA source at an energy of 40 keV and a dose of 5.0 × 1017 ions cm−2. Electrochemical impedance spectroscopy (EIS) was used to study the influence of the ions implantation on electrochemical behavior of anodic films in basic NaCl solution. The results show that Ni ions implantation strengthens the self-sealing process of the anodic film in solutions. The resistance of the porous layer (Rp) increases and the capacitance of the porous layer (Cp) decreases after implantation of Ni ions. For the anodic layer without implantation of Ni ions, as the immersion time increases, changes of Cp and Rp are slower. A more rapid change is observed for the anodic films implanted with Ni ions. XPS results reveal that Ni is present on the anodic film surface as metallic Ni and nickel oxide (NiO). AFM results show that the implantation of Ni ions made the surface structure and morphology of anodic films more uniform and less rough. The semi conductive property of anodic films in basic NaCl solution with and without Ni ions implantation was studied by Mott–Schottky analysis. For anodic films implanted with Ni ions, the profile is characteristic of p-type semiconductors from −1.0 V to −0.5 V. By expanding the M–S plots at high potentials to more positive potential than −0.5 V, the anodic film shows n-type characteristic. Possible reasons for the observed changes in surface properties are discussed.
Co-reporter:Jianjun Ren, Yu Zuo
Surface and Coatings Technology 2005 Volume 191(2–3) pp:311-316
Publication Date(Web):21 February 2005
DOI:10.1016/j.surfcoat.2004.04.054
Pitting behaviour and pit morphology on anodized pure aluminum in NaCl solution were studied with an electrochemical method and scanning electron microscope (SEM). Severe pitting happened at high potential for anodized pure aluminum. Polarization curves show that the pitting process was diffusion controlled. Many pits with various sizes were observed on sample surfaces after polarization. Some pits developed to several hundreds of microns in diameter, but with the anodic films remaining as covers of the pits. Small openings were seen on the film covers as the diffusion channels for dissolved species within the pits, which reveals that the pits developed in a highly occluded state. The pits show different shapes from hemispherical to oblate. The ratio of pit radius to pit depth, R/t, is proportional to the ratio of pit opening radius to pit radius, r/R. The bigger the ratio r/R is, the more oblate the pit shape is. A modified diffusion controlled model is suggested to explain the formation of oblate pits.
Co-reporter:Yuming Tang, Yu Zuo
Materials Chemistry and Physics 2004 Volume 88(Issue 1) pp:221-226
Publication Date(Web):15 November 2004
DOI:10.1016/j.matchemphys.2004.07.014
The metastable pitting behavior of mild steel in 0.5 M NaHCO3 solutions containing different concentrations of Cl− was studied with potentiodynamic and potentiostatic polarization methods. Current fluctuations occurred before stable pitting, with the characteristic of quick increase and slow decrease. The occurring potential for metastable pitting Em obeys normal distribution, and decreases with the increase of chloride concentration. Potential has no apparent effect on the frequency of fluctuations. In potentiostatic test, when potential is above Em and far below the pitting breakdown potential Eb, the current fluctuations remain for a period then disappear, resulting in pits with diameters of microns. When potential is close to Eb, the polarization current may finally rises continuously after a certain time of fluctuations, and metastable pitting is replaced by stable pitting.
Co-reporter:Jianjun Ren, Yu Zuo
Surface and Coatings Technology 2004 Volume 182(2–3) pp:237-241
Publication Date(Web):22 April 2004
DOI:10.1016/j.surfcoat.2003.08.082
Pitting behavior of anodized 2024 aluminum alloy in NaCl solution was studied using electrochemical methods and SEM. Three stages were observed during potentiostatic polarization of the anodized alloy. In the first stage, current decreases with time, following the relation log i=−n log t, where parameter n indicates the passivation tendency of the alloy. The stage corresponds to the induction time for pitting and increased chloride concentration will shorten the stage. After the induction time, pitting happens and the current begins to increase continuously. In the third stage, the current reaches a stable value, and the growth of pits is controlled by ohmic drop. The relationship between pitting potential of the anodized alloy and chloride concentration in the solution follows the expression Ep=A−B log[Cl−]. On anodized 2024 aluminum alloy pits develop preferentially along the interface between the anodic film and the substrate. Large, shallow pits were formed.
Co-reporter:Yu Zuo, Peng-Hui Zhao, Jing-Mao Zhao
Surface and Coatings Technology 2003 Volume 166(2–3) pp:237-242
Publication Date(Web):24 March 2003
DOI:10.1016/S0257-8972(02)00779-X
The influences of sealing methods on the corrosion behavior of three anodized aluminum alloys, 1070, 2024 and 7075, in NaCl solutions were studied. The anodic films were sealed by the methods of boiling water, stearic acid, potassium dichromate and nickel fluoride, respectively. Passivation and pitting behaviors resulting from the sealing treatments were studied using the potentiodynamic polarization, and surface morphology was examined by scanning electron microscopy. The results show that boiling water and potassium dichromate sealed films provide relatively higher corrosion resistance in acidic solution, while nickel fluoride sealed film is better in basic solution. Stearic acid sealed film provides good corrosion resistance both in acidic and in basic solutions. The influencing mechanisms of different sealing methods on corrosion resistance of the anodized alloys were discussed.
Co-reporter:C. Guo, C.J. Han, Y.M. Tang, Y. Zuo, S.Z. Lin
Engineering Failure Analysis (April 2011) Volume 18(Issue 3) pp:890-894
Publication Date(Web):1 April 2011
DOI:10.1016/j.engfailanal.2010.11.003
The cracking of 0Cr13Al stainless steel tube bundle in condensate/heavy gas oil (HGO) heat exchanger in a petrochemical plant was studied to investigate the failure mechanism. The chemical composition, elements distribution and the morphology of the cracks were analyzed. The results showed that intergranular stress corrosion cracking (ISCC) was the main reason for this failure, and welding microfissures promoted the failure. Strict welding processes, and materials that are not susceptible to intergranular cracking, such as TP321 stainless steel, are suggested to avoid such failures in future application.
Co-reporter:Yun Zhou, Yu Zuo, Bing Lin
Materials Chemistry and Physics (1 May 2017) Volume 192() pp:
Publication Date(Web):1 May 2017
DOI:10.1016/j.matchemphys.2017.01.083
•Compound Na2MoO4 + BTA showed good inhibition for steel in NaCl + NaHCO3 solution.•Pitting corrosion potential increased obviously by adding compound Na2MoO4 + BTA.•The inhibition film was mainly composed of FeMoO4 and BTA-Fe.•The BTA-Fe/FeMoO4 structure improved the compactness of the inhibition film.•The compound inhibitor promoted transformation of FeOOH to Fe2O3 in passive film.The compounded inhibition of Na2MoO4 and benzotriazole (BTA) on pitting corrosion of Q235 steel in 0.01 mol L−1 NaCl + 0.1 mol L−1 NaHCO3 solution was studied by methods of polarization, XPS and SEM. The results show that the compounded Na2MoO4 and BTA obviously strengthened the inhibition on steel and the optimal ratio of Na2MoO4 and BTA was 4:1. In the test solution with the compounded inhibitor (pH 8.16–10), the pitting corrosion potential increased obviously and the inhibition efficiency remained above 97%. With immersion time extended, the inhibition film thickened and the inhibition effect increased. The pitting potential increased with immersion time in 36 h, then remained stable around the transpassive potential and pitting corrosion was almost inhibited. The inhibition film was mainly composed of FeMoO4 and BTA-Fe. The compounded inhibitors facilitated adsorption and film formation for both Na2MoO4 and BTA on steel surface. In addition, the compounded inhibitors promoted the transformation of FeOOH to Fe2O3 in the passive film, which further strengthened stability of the passive film.
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