Zn-Al coatings can provide protection to exposed steel parts in most environments. For this reason, the investigation of Zn-Al coatings become very popular in recent years. In order to study the microstructures and pr...Zn-Al coatings can provide protection to exposed steel parts in most environments. For this reason, the investigation of Zn-Al coatings become very popular in recent years. In order to study the microstructures and properties of mechanically deposited Zn-Al coating, zinc powders and aluminum powders were used to deposit Zn-AI coating by mechanical plating. The microstruetures, phase constitutes and compositions of the coating were observed and analyzed with optical microscopy （OM）, scanning electron microscopy（SEM）, X-ray diffraction（XRD） and X-ray energy-dispersive spectroscopy（EDS）. The results of observation show that the coating consists of almost spherically shaped zinc particles point contacting with each other; the coatings are composed of zinc particles, aluminum particles, interstice, and tin; extra fine zinc powders and some smaller interspersed inclusions are positioned in the interstices. Porosity and thickness of the coating were tested by ferroxyl test and magnetic method. The corrosion resistance of coatings was studied by neutral salt spraying test（NSS）, immersion test and electrochemical polarization. It is found that the thickness of the coating dose lacks uniformity, with an uneven thickness distribution and an average variation of approximately 2-5gm; the coating can afford cathodic protection to the steel substrate; the corrosion resistance of Zn-Al coatings is better than that of the mechanically plated zinc coatings with same thickness. These conclusions can be applied to improve anti-corrosion performance by mechanically deposit Zn-Al coatings.展开更多
A new hot-dip galvanizing method was employed on hot-rolled low carbon steel.The effects of Al contents on microstructure,micro-hardness and corrosion resistance of Zn-Al alloy coatings were systematically investigate...A new hot-dip galvanizing method was employed on hot-rolled low carbon steel.The effects of Al contents on microstructure,micro-hardness and corrosion resistance of Zn-Al alloy coatings were systematically investigated.Phase composition,microstructure and element distribution in Zn-Al alloy coatings were analyzed using X-ray diffraction（XRD）and electron probe micro analysis（EPMA）,respectively.It is found that Al content（0.6-6.0 wt.%）in galvanizing zinc affects surface quality and adhesion between coatings and matrix in the newly developed method.In addition,with increasing Al content,micro-hardness significantly increased due to the increase in Zn-Al eutectoid phases.Potentiodynamic polarization and electrochemical impedance spectroscopy（EIS）also revealed that increase in Al plays a noticeable role in improving the corrosion resistance of Zn-Al alloy coatings.展开更多
基金supported by National Natural Science Foundation of China (Grant No. 50561003)Foundation of Yunnan Provincial Education Department of China (Grant No.07Y41414)
文摘Zn-Al coatings can provide protection to exposed steel parts in most environments. For this reason, the investigation of Zn-Al coatings become very popular in recent years. In order to study the microstructures and properties of mechanically deposited Zn-Al coating, zinc powders and aluminum powders were used to deposit Zn-AI coating by mechanical plating. The microstruetures, phase constitutes and compositions of the coating were observed and analyzed with optical microscopy （OM）, scanning electron microscopy（SEM）, X-ray diffraction（XRD） and X-ray energy-dispersive spectroscopy（EDS）. The results of observation show that the coating consists of almost spherically shaped zinc particles point contacting with each other; the coatings are composed of zinc particles, aluminum particles, interstice, and tin; extra fine zinc powders and some smaller interspersed inclusions are positioned in the interstices. Porosity and thickness of the coating were tested by ferroxyl test and magnetic method. The corrosion resistance of coatings was studied by neutral salt spraying test（NSS）, immersion test and electrochemical polarization. It is found that the thickness of the coating dose lacks uniformity, with an uneven thickness distribution and an average variation of approximately 2-5gm; the coating can afford cathodic protection to the steel substrate; the corrosion resistance of Zn-Al coatings is better than that of the mechanically plated zinc coatings with same thickness. These conclusions can be applied to improve anti-corrosion performance by mechanically deposit Zn-Al coatings.
基金the National Science and Technology Pillar Program of China (2011BAE13B04)National Natural Science Foundation of China(51204047and U1660117)Fundamental Research Funds for the Central Universi-ties of China(N130407004)for the financial support
文摘A new hot-dip galvanizing method was employed on hot-rolled low carbon steel.The effects of Al contents on microstructure,micro-hardness and corrosion resistance of Zn-Al alloy coatings were systematically investigated.Phase composition,microstructure and element distribution in Zn-Al alloy coatings were analyzed using X-ray diffraction（XRD）and electron probe micro analysis（EPMA）,respectively.It is found that Al content（0.6-6.0 wt.%）in galvanizing zinc affects surface quality and adhesion between coatings and matrix in the newly developed method.In addition,with increasing Al content,micro-hardness significantly increased due to the increase in Zn-Al eutectoid phases.Potentiodynamic polarization and electrochemical impedance spectroscopy（EIS）also revealed that increase in Al plays a noticeable role in improving the corrosion resistance of Zn-Al alloy coatings.
