The influence of phosphating bath at different temperatures on the formation and corrosion property of calcium-modified zinc phosphate conversion coating （Zn-Ca-P coating） on Mg-Li-Ca alloy was investigated. The mor...The influence of phosphating bath at different temperatures on the formation and corrosion property of calcium-modified zinc phosphate conversion coating （Zn-Ca-P coating） on Mg-Li-Ca alloy was investigated. The morphologies, elemental distribution and chemical structures of the coatings were examined via SEM, EPMA, EDS, XRD and FT-IR. The corrosion resistance was assessed by hydrogen evolution, potentiodynamic polarization and EIS. The results show that the coating is composed of single element Zn and ZnO at below 45 ℃;whereas the coatings are predominantly characterized by Zn3（PO4）2·4H2O and small amount of element zinc and ZnO at above 50 ℃. Mg-Li-Ca alloy with Zn-Ca-P coatings prepared at 55 ℃ has the highest corrosion resistance. However, the hydrogen evolution rates of the coatings obtained at 40-50 ℃ is accelerated due to the galvanic corrosion between the imperfection of the single element Zn coating and the Mg substrate.展开更多
A Cu/Al galvanic couple was established to study the influence of the oxidantKMnO_4 on the film-forming process of rare earth metal (REM) conversion coating on LY12 aluminumalloy. It is found that the galvanic couple ...A Cu/Al galvanic couple was established to study the influence of the oxidantKMnO_4 on the film-forming process of rare earth metal (REM) conversion coating on LY12 aluminumalloy. It is found that the galvanic couple simulative experiment accords with the actual immersion,and it can be substantially used to simulate the behavior of LY12 aluminum alloy in thefilm-forming process. It is showed that the formation of the coating is quickened in CeCl_3 solutioncontaining KMnO_4 compared with that not containing KMnO_4. XPS results reveal that the coatingformed on cathode is composed of oxide or hydroxide of Ce and Mn, so the mechanism of formation ofREM conversion coating changes when KMnO4 is added.展开更多
In order to accelerate the conversion coating formation on 6063 Al alloy in the Ce(NO3)3 solution, accelerants of chloride and ammonium salt were used. The coating morphology, composition and structure were analyzed w...In order to accelerate the conversion coating formation on 6063 Al alloy in the Ce(NO3)3 solution, accelerants of chloride and ammonium salt were used. The coating morphology, composition and structure were analyzed with SEM/EDS, EPMA, XPS and XRD. The coating morphology is influenced by the composition, pH value and temperature of the treating solution. The coating composed of metal oxide, metal hydroxide and hydrate appears to be amorphous. The elements in the coating are Al, Ce, O, Mn and Mg, while the Ce element exists in the forms of Ce3+ and Ce4+. The accelerant of chloride can increase the compactness and Ce content of the coating, so the coating corrosion resistance is remarkably improved. A scheme for the electrochemical reaction in the coating formation was proposed, and the potential change in the coating formation was also studied. It is found that chloride can shorten the time period of the first and the second stages in coating formation.展开更多
In order to improve the hot corrosion resistance of DZ125 alloy,Ce-Y modified aluminum coatings were prepared on DZ125 alloy by pack cementation process at 950°C for 2 h.The microstructure,phase constitution and ...In order to improve the hot corrosion resistance of DZ125 alloy,Ce-Y modified aluminum coatings were prepared on DZ125 alloy by pack cementation process at 950°C for 2 h.The microstructure,phase constitution and formation mechanism of the coatings were investigated.The hot corrosion behaviors of DZ125 alloy and the coatings in molten salt environment of 25%K2SO4+75%Na2SO4(mass fraction)at 900°C were studied.Results show that the obtained Al-Ce-Y coatings were mainly composed of Al3Ni2,Al3Ni and Cr7Ni3,with a thickness of about 120μm.After hot corrosion test,DZ125 alloy suffered catastrophic hot corrosion and serious internal oxidation and internal sulfidation arose.Two layers of corrosion products formed on surfaces of DZ125 alloy,including the outer layer consisting of Cr2O3 and NiCr2O4,and the inner layer of Al2O3,Ni3S2 and Ni-base solid solution.After being coated with Al-Ce-Y coating,the hot corrosion resistance of DZ125 alloy is improved notably,due to the formation of a dense scale mainly consisting of Al-rich Al2O3 in the coating layer.展开更多
基金Project(51241001)supported by the National Natural Science Foundation of ChinaProject(ZR2011EMM004)supported by the Natural Science Foundation of Shandong Province,China+1 种基金Project(SKLCP21012KF03)supported by the Open Foundation of State Key Laboratory for Corrosion and Protection,ChinaProject(TS20110828)supported by Taishan Scholarship Project of Shandong Province,China
文摘The influence of phosphating bath at different temperatures on the formation and corrosion property of calcium-modified zinc phosphate conversion coating （Zn-Ca-P coating） on Mg-Li-Ca alloy was investigated. The morphologies, elemental distribution and chemical structures of the coatings were examined via SEM, EPMA, EDS, XRD and FT-IR. The corrosion resistance was assessed by hydrogen evolution, potentiodynamic polarization and EIS. The results show that the coating is composed of single element Zn and ZnO at below 45 ℃;whereas the coatings are predominantly characterized by Zn3（PO4）2·4H2O and small amount of element zinc and ZnO at above 50 ℃. Mg-Li-Ca alloy with Zn-Ca-P coatings prepared at 55 ℃ has the highest corrosion resistance. However, the hydrogen evolution rates of the coatings obtained at 40-50 ℃ is accelerated due to the galvanic corrosion between the imperfection of the single element Zn coating and the Mg substrate.
基金[This work was financially supported by the National Natural Science Fund of China (No.59771067).]
文摘A Cu/Al galvanic couple was established to study the influence of the oxidantKMnO_4 on the film-forming process of rare earth metal (REM) conversion coating on LY12 aluminumalloy. It is found that the galvanic couple simulative experiment accords with the actual immersion,and it can be substantially used to simulate the behavior of LY12 aluminum alloy in thefilm-forming process. It is showed that the formation of the coating is quickened in CeCl_3 solutioncontaining KMnO_4 compared with that not containing KMnO_4. XPS results reveal that the coatingformed on cathode is composed of oxide or hydroxide of Ce and Mn, so the mechanism of formation ofREM conversion coating changes when KMnO4 is added.
基金Project(2007B00031800003) supported by the Scientific and Technological Plan of Guangdong Province, ChinaProject(2005040153) supported by the Development Foundation of Science and Technology of Foshan City, ChinaProject(20080203) supported by the Postdoctoral Innovation Fund of South China University of Technology, China
文摘In order to accelerate the conversion coating formation on 6063 Al alloy in the Ce(NO3)3 solution, accelerants of chloride and ammonium salt were used. The coating morphology, composition and structure were analyzed with SEM/EDS, EPMA, XPS and XRD. The coating morphology is influenced by the composition, pH value and temperature of the treating solution. The coating composed of metal oxide, metal hydroxide and hydrate appears to be amorphous. The elements in the coating are Al, Ce, O, Mn and Mg, while the Ce element exists in the forms of Ce3+ and Ce4+. The accelerant of chloride can increase the compactness and Ce content of the coating, so the coating corrosion resistance is remarkably improved. A scheme for the electrochemical reaction in the coating formation was proposed, and the potential change in the coating formation was also studied. It is found that chloride can shorten the time period of the first and the second stages in coating formation.
基金Project(51961003)supported by the National Natural Science Foundation of ChinaProject(NGY2018-148)supported by the Science and Technology Research of Ningxia Colleges,ChinaProject(NZ16083)supported by Key Program of Natural Science Foundation of Ningxia,China
文摘In order to improve the hot corrosion resistance of DZ125 alloy,Ce-Y modified aluminum coatings were prepared on DZ125 alloy by pack cementation process at 950°C for 2 h.The microstructure,phase constitution and formation mechanism of the coatings were investigated.The hot corrosion behaviors of DZ125 alloy and the coatings in molten salt environment of 25%K2SO4+75%Na2SO4(mass fraction)at 900°C were studied.Results show that the obtained Al-Ce-Y coatings were mainly composed of Al3Ni2,Al3Ni and Cr7Ni3,with a thickness of about 120μm.After hot corrosion test,DZ125 alloy suffered catastrophic hot corrosion and serious internal oxidation and internal sulfidation arose.Two layers of corrosion products formed on surfaces of DZ125 alloy,including the outer layer consisting of Cr2O3 and NiCr2O4,and the inner layer of Al2O3,Ni3S2 and Ni-base solid solution.After being coated with Al-Ce-Y coating,the hot corrosion resistance of DZ125 alloy is improved notably,due to the formation of a dense scale mainly consisting of Al-rich Al2O3 in the coating layer.
