Most hulls of the ships are protected with paintings, sacrificial anode, and impressed current cathodic protection methods against corrosion problems. However, these conventional methods are not very effective because...Most hulls of the ships are protected with paintings, sacrificial anode, and impressed current cathodic protection methods against corrosion problems. However, these conventional methods are not very effective because the rudder of ships stern are exposed to very severe corrosive environment such as tides, speeds of ships, cavitations and erosion corrosion. The environmental factors such as cavitation and corrosion will cause damage for materials with the shock wave by the creation and destruction of bubble. To solve these problems, the cavitation and electrochemical experiments are executed for thermal spray coating with Al-Zn alloy wire material. Thereafter, and sealed specimens with F-Si sealer on Al-Zn alloy coated specimen are executed to improve electrochemical and anti-cavitation characteristics in sea water. The application of fluorine silicon sealing after spray coating of 15%Al-85%Zn seems to be appropriate not only in static environment but also in dynamic environment.展开更多
An A1 coating on Mg substrate was achieved by droplet spraying treatment. The microstructure was studied by electron probe microanalysis （EPMA） and X-ray diffraction （XRD）. The coating layer is composed of AI phas...An A1 coating on Mg substrate was achieved by droplet spraying treatment. The microstructure was studied by electron probe microanalysis （EPMA） and X-ray diffraction （XRD）. The coating layer is composed of AI phase and exhibits superior corrosion resistance. The formation of the coating is mainly attributed to the obstruction of expansion of the transition zone by primarily solidified Mg]7All2 during rapid cooling, and the diffusion is restricted in a thin layer. These results show that droplet spraying is a promising way to protect magnesium by using corrosion-resistant materials available now.展开更多
In the continuous hot-dip galvanizing process, the gas-jet wiping is used to control the coating thickness of moving steel strip. The high speed gas-jet discharged from the nozzle slot impinges on the strip, and at th...In the continuous hot-dip galvanizing process, the gas-jet wiping is used to control the coating thickness of moving steel strip. The high speed gas-jet discharged from the nozzle slot impinges on the strip, and at this moment, wipes the liquid coating layer dragged by a moving strip. The coating thickness is generally influenced on the flow characteristics of wiping gas-jet such as the impinging pressure distribution, pressure gradient and shear stress distribution on the surface of strip. The flow characteristics of wiping gas-jet mentioned above depends upon considerably both the process operating conditions such as the nozzle pressure, nozzle-to-strip distance and line speed, and the geometry of gas-jet wiping apparatus such as the height of nozzle slot. In the present study, the effect of the geometry of nozzle on the coating thickness is investigated with the help of a computational fluid dynamics method. The height of nozzle slot is varied in the range of 0.6mm to 1.7mm. A finite volume method (FVM) is employed to solve two-dimensional, steady, compressible Navier-Stokes equations. Based upon the results obtained, the effect of the height of nozzle slot in the gas-jet wiping process is discussed in detail. The computational results show that for a given standoff distance between the nozzle to the strip, the effective height of nozzle slot exists in achieving thinner coating thickness.展开更多
文摘Most hulls of the ships are protected with paintings, sacrificial anode, and impressed current cathodic protection methods against corrosion problems. However, these conventional methods are not very effective because the rudder of ships stern are exposed to very severe corrosive environment such as tides, speeds of ships, cavitations and erosion corrosion. The environmental factors such as cavitation and corrosion will cause damage for materials with the shock wave by the creation and destruction of bubble. To solve these problems, the cavitation and electrochemical experiments are executed for thermal spray coating with Al-Zn alloy wire material. Thereafter, and sealed specimens with F-Si sealer on Al-Zn alloy coated specimen are executed to improve electrochemical and anti-cavitation characteristics in sea water. The application of fluorine silicon sealing after spray coating of 15%Al-85%Zn seems to be appropriate not only in static environment but also in dynamic environment.
基金Project(J12LA53)supported by Shangdong Provincial Higher Education Science and Technology Program,ChinaProject(KZJ-48)supported by the Science and Technology Development Program of Qingdao,China
文摘An A1 coating on Mg substrate was achieved by droplet spraying treatment. The microstructure was studied by electron probe microanalysis （EPMA） and X-ray diffraction （XRD）. The coating layer is composed of AI phase and exhibits superior corrosion resistance. The formation of the coating is mainly attributed to the obstruction of expansion of the transition zone by primarily solidified Mg]7All2 during rapid cooling, and the diffusion is restricted in a thin layer. These results show that droplet spraying is a promising way to protect magnesium by using corrosion-resistant materials available now.
文摘In the continuous hot-dip galvanizing process, the gas-jet wiping is used to control the coating thickness of moving steel strip. The high speed gas-jet discharged from the nozzle slot impinges on the strip, and at this moment, wipes the liquid coating layer dragged by a moving strip. The coating thickness is generally influenced on the flow characteristics of wiping gas-jet such as the impinging pressure distribution, pressure gradient and shear stress distribution on the surface of strip. The flow characteristics of wiping gas-jet mentioned above depends upon considerably both the process operating conditions such as the nozzle pressure, nozzle-to-strip distance and line speed, and the geometry of gas-jet wiping apparatus such as the height of nozzle slot. In the present study, the effect of the geometry of nozzle on the coating thickness is investigated with the help of a computational fluid dynamics method. The height of nozzle slot is varied in the range of 0.6mm to 1.7mm. A finite volume method (FVM) is employed to solve two-dimensional, steady, compressible Navier-Stokes equations. Based upon the results obtained, the effect of the height of nozzle slot in the gas-jet wiping process is discussed in detail. The computational results show that for a given standoff distance between the nozzle to the strip, the effective height of nozzle slot exists in achieving thinner coating thickness.
