Preparation of tetrapod-like ZnO whiskers from waste hot dipping zinc

Large and uniform tetrapod-like ZnO whiskers （T-ZnO） were prepared from waste hot dipping zinc by vapor oxidation and examined by means of X-ray diffraction and ICP-AES analysis and scanning electron microscope. The products are pure hexagonal wurtzite crystals with tetrapod shape and edge size of center body 56 μm and needle length of 100130 μm. The size and shape of ZnO particles are fully controlled by the growth conditions and T-ZnO can be obtained only at 8501 000 ℃ and total gas flow rate ranging from 40 to 250 L·h-1 in which the size of the T-ZnO particles varies slightly with temperature. The process of the formation of T-ZnO is that T-ZnO may nucleate at the initial stage with a complete tetrapod shape and develop to the large size, but not the process of （preferential） growth of octahedral nuclei and subsequent growth of the needles. The experiment presents a new method to prepare T-ZnO economically by using the waste hot dipping zinc.

CORROSION RESISTANCE OF HOT DIP GALVANIZED STEEL PRETREATED WITH BIS-FUNCTIONAL SILANES MODIFIED WITH NANOALUMINA

The corrosion behavior of hot dip galvanized steel pretrvated with bis-[triethoxysilylpropyl] tetrasulfide （BTESPT） modified with alumina particles was studied. The corrosion resistance of the passiving films was evaluated by Tafel polarization curve and electrochemical impedance spectroscopy. The films formed on the galvanized steel substrate were characterized by Fourier transform infrared spectroscopy and energy dispersive X-ray spectrometry. The surface morphology of the treated hot dip galvanized steel samples was observed by Field Emission Scanning Electron Microscope. The results show that the pretrvatments on the basis of silane films modified with nanoalumina particles have reduced both anodic and cathodic current densities, and increased total impedance in the measured frequency, consequently, improving corrosion protection for hot dip galvanized steel during immersion in NaCl solutions compared to chromate films and silane films.

Development of Hot Dip Galvanized Steel Strip and Its Application in Automobile Industry

Hot dip galvanized product is widely used in architecture, household electric appliance, ship vehicle, vessel, mechano-electronic device and other fields including clothing, food, housing, and travel. The history, development, market need, and technological advancement of hot dip galvanized strip, production situation, and development tendency in China are briefly introduced. The fact that it is necessary to build new and auto galvanized strip line with the development of the iron and steel industry in China.

THE INFLUENCE OF COMPOSITION AND TEMPERATURE OF BATH ANDAFTER-TREATMENT 0N COLORATION IN COLORING HOT DIPGALVANIZATION

The 08 Al steel sheets were hot dip ped into Zn - Mn bath with 0 1 % Mn and 0 2 % Mn at600 ～420 ℃ bath tem perature , and then w ere treated in different w ays . The after - treat ments include cooling in the air at room tem perature directly , holding at the upper part of thehot dip galvanizing furnace for 60 s an d then holding at 510 ±10 ℃for 90 s . The results in dicated that blue , yellow , and purple , w hose coloration varied with the co m position an d thetem perature of bath and the w ays of after - treat ment . Finally , the mechanism of coloredzinc coating w as discussed .

Heat Transfer during the Solidification of Hot Dip Aluminizing Coating

Hot dip aluminizing is one of the most effective methods of surface protection for steels and is gradually gaining popularity.Although the pulling speed is one of the most important parameters to control the coating thickness of aluminizing products,however,there are few publications on the mathematical modeling of pulling speed during the hot dip process.In order to describe the correlation among the pulling speed,coating thickness and solidification time,the principle of mass and heat transfer during the aluminizing process is investigated in this paper.The mathematical models are based on Navier-Stokes equation and heat transfer analysis.Experiments using the self-designed equipment are carried out to validate the mathematical models.Specifically,aluminum melt is purified at 730 ℃.The Cook-Norteman method is used for the pretreatment of Q235 steel plates.The temperature of hot dip aluminizing is set to 690 ℃ and thedipping time is set to 3 min.A direct current motor with stepless speed variation is used to adjust the pulling speed.The temperature change of the coating is recorded by an infrared thermometer,and the coating thickness is measured by using image analysis.The validate experiment results indicate that the coating thickness is proportional to the square root of pulling speed for the Q235 steel plate,and that there is a linear relationship between coating thickness and solidification time when the pulling speed is lower than 0.11 m/s.The prediction of the proposed model fits well with the experimental observations of the coating thickness.

Effect of Mischmetal on Oxidation Resistance of 55Al－Zn Alloy Hot Dip Coating

The effect of mischmetal addition on high temperature oxidation resistance of 55wt% Al43.4 wt% Zn-1 .6wt% Si alloy hot-dip coatings has been investigated. It is found that rare earth addition improves high temperature oxidation resistance of the coatings. The oxidation tests at 800℃, 100 h and 1000℃, 50 h show that the coating with addition of 0. 1 % RE has the best properties. The morphology of oxide scale and element distribution of coating section were analysed by SEM, EPMA and XRD. It is indicated that mischmetal addition improves the adhesion between oxide scale and coating substrate, and spalling resistance of the scale is also improved with the addition of RE. Additionally, RE controls the degeneracy speed of Al-content in the coatings and inhibits the growth of Fe-Al intermetallic compound. For this reason, higher Al-content is kept in all the coatings with RE addition.

The new technical progress of hot dip galvanizing process without sink roll

In this paper,the recent state and problems of the sink roll in CGL are described.Several methods of increasing its operational life span are introduced,such as surface coating technology and sleeve material technology.Fundamentally they cannot solve the problems of surface quality caused by the contact between strip and roll.On this basis,the newly developed principle and solutions for hot dip galvanizing technology without sink roll are highly emphasized,they are Float Technology,Electromagnetic pump technology,Electromagnetic enclosed slot by high-frequency AC,Electromagnetic enclosed slot by high-frequency DC.A comparison among their functions and characteristics is made and the possibility of its application is also discussed.Finally it comes to a conclusion that electromagnetic enclosed slot represents the direction of a continuous hot-dip galvanizing steel strip in the the 21st century.It has a very broad application prospects.Baosteel Technology Center is focused on the research and development of this technology.As technology advances,industrial applications is possible.

Effect of Pb content on the surface topography and corrosion resistance of hot dip Zn-Al-Mg coatings

In this study,the effect of Pb content on the surface morphology and salt spray corrosion resistance of hot dip Zn-AI-Mg coatings was investigated. The results showed that the coating surface easily formed small grains of zinc spangle structures and that the salt spray con＇osion resistance of the coating decreased when Pb content was greater than 0.01%. The microstructure and energy dispersive spectrum analysis of surface and cross-sectional areas was performed by scanning electron microscopy. Pb content present in the coating was analyzed by glow discharge spectrum. The results showed that the distribution of Pb in the coating was not uniform. The Pb content was segregated on the surface and at the cross-section of the Zn-A1-MgZn2 ternary eutectic structure,especially,on the surface of the Zn-A1-MgZn2 ternary eutectic structure.

Simulation analysis of hot dip galvanizing process parameters based on orthogonal experimental design

An iron and steel company＇ s hot galvanizing technology was chosen as the object. An orthogonal experimental scheme with 5 factors of mixed level was designed, according to the various factors affecting the distribution of slag. For each scheme, the amount of slag and slag height in different orthogonal schemes by simulation were obtained with FLUENT software. Then, range and variance analyses were selected to compare the trend of slag height in the different process parameters of the hot dip galvanizing process. Finally, the optimal combination of the process parameters was obtained.

A SRUDY ON CORROSION RESISTANCE OF DIFFERENT MATERIAL IN CONDENSATE WATER FROM A NATURAL GAS PURIFYING STATION

The corrosion behaviors of different material in the condensate water from the natural gas purifying station were studied by laboratory tests, field tests and measurements of polarization curve. The results showed that hot dipping aluminum steel had a good corrosion resistance to the accompanying gas of crude oil and condensate water in the natural gas purifying station.

Investigation of the transformation of sink-roll groove-mark defect in the galvannealing process

The influence of galvannealing on the transformation of the sink-roll groove-mark defect was studied by comparing the defects on galvannealed( GA) coating with those on galvanized( GI) coating. It was found that defects on GI coating contained high amounts of aluminum,zinc dross,and a zinc-iron intermetallic outburst structure,as well as slight scratches on the substrate. After being galvannealed,the aluminum content was higher and there was a much greater outburst structure,which made the coating of the defect thicker than the normal coating,while the zinc dross and scratches on the substrate had disappeared due to zinc and iron diffusion during the galvannealing process.

Activities of binary baths with 1% solute as standard states

The relationships of activities with 1% solute as standard state and mass fraction of solute, and hot dip temperature, were given on the base of Miedema’s model, Tanaka expression, some basic thermodynamic relationships; and discussion was carried out on Zn Mn and Zn Ti binary alloys by calculation, in which varied colors can be achieved onthe hot dip steel sheets. The results indicate that the activity of solute shows positive deviation relative to Henry’s law for both Zn Mn and Zn Ti binary dilute solution. The degree of deviation increases with increasing solute and decreases with increasing bath temperature. As the solution is very dilute solution ( w (Mn)≤40% for Zn Mn alloy, w (Ti)≤8% for Zn Ti alloy), the two binary baths can all be treated as ideal dilute solutions. [

Manufacturing process and microstructure of copper-coated aluminum wires

Copper-coated aluminum wires exhibit good electrical conductivity, high thermal conductivity, low contact resistance of copper and low density, and provide economic advantages over aluminum. However, there are some problems in the manufacring processes of hot-dip copper-coated aluminum wires, such as the difficulties in controlling coating process. In this work, the hot-dip copper-coating method of aluminum wires was investigated for producing copper-coated aluminum wire composites. The interface microstructure between the aluminum wire and the copper coating layer was analyzed by scanning electron microscopy （SEM） and energy-dispersive X-ray spec- trometry （EDS）. Five different fluxing agents were tested. Experimental results show that appropriate conditions for the hot-dip process are determined as the liquid copper temperature of 1085℃ and the treatment time less than 1 s. A success in hot-dip copper-coated aluminum wires is achieved by hot-dipping a low-melting-point metal into a high-melting-point metal liquid, which is significant for the further devel- opment and application of copper-coated aluminum wire composites.

The development of surface treatment products and technologies of steel sheets in Baosteel

The surface treatment technology can improve the corrosion resistance of steel sheets and increase the value of steel application.The surface treated steel sheets in Baosteel include zinc galvanized steel sheets,sin galvanized steel sheets,chromium galvanized steel sheets,and colour coating steel sheets with the application in the area from construction to automobiles,appliance,package,etc.The development,application and manufacturing technique of these products have become the core competition power of Baosteel. The article reviews the developments of surface treated steel sheets and surface treatment technologies in Baosteel in 10 years,especially hot dip galvanized high strength steel products used in vehicles.The article also looks forward into further developments of surface treatment steel products and technologies in Baosteel,which will focus on:①the new products of hot dip galvanized advanced high strength steels;②more environmental friendly products or functional coating products;③the development of surface treatment technologies to meet the requirement of higher surface quality in the marcket;④new type of surface treatment and coating technologies.

Optimising the corrosion performance of pre-painted steels

Pre-painted steel is one of the most important structural material of the 20th century well known for its excellent corrosion resistance and wide ranging applications.A typical pre-painted steel usually consists of a layer of metal coating system,preferably zinc or zinc alloy coating and a combination of layers of inorganic - organic coatings usually referred to as paint system.The corrosion resistance of the metal coating as well as the paint system may vary considerably based on their composition and the environment.For optimal corrosion performance of pre-painted steel,a judicious selection of both metal and inorganic-organic coating systems are essential.This paper reviews different types of possible corrosion issues in pre-painted steels and methods to optimise their performance.

Electroless Plating Lead and Lead-Tin on Copper Using an Eco-Friendly Plating Bath

Copper serpentines used in gas heaters are currently coated with lead-tin alloy using hot-dip technology where copper is immersed in molten lead (98%)-Tin at about 400°C. The major drawback of this technique is the pollution resulted from lead vapors which cause much harm to the labors in the unit. The present work investigates an eco-friendly plating technique to replace the currently used technology. Electroless plating of copper samples with lead or Lead (98%)-Tin alloy is carried out from a plating bath contained lead salt, tin salt, reducing agent and stabilizing agent. The parameters affecting the coating quality such as the plating time, temperature and bath composition were optimized. The chemical analysis and coating morphology of the formed coatings are examined by XRD, SEM and EDS to reach the best bath composition as well as the best conditions to coat copper with lead or lead-tin electrolessly. The electrochemical properties of copper and copper coated samples are also examined using electrochemical impedance spectroscopy.

Effect of rare earth content on microstructure and corrosion resistance of hot-dip Zn-5Al alloy coated steel wire for bridge cables

The effects of the content of rare earth elements on the microstructure and properties of hot-dip Zn-5 Al alloy steel wire for bridge cables were investigated.The microstructure of the hot-dip coating was analyzed using an optical microscope and a scanning electron microscope equipped with an energy-dispersive spectrometer.The bonding force between the hot-dip coating and steel wire was determined by the winding test.The corrosion resistance of the steel wire hot-dip coating was tested by the electrochemical workstation.The hot-dip Zn-5A1 alloy coating has a corrosion-resistant structure composed of a zinc-rich phase and an aluminum-rich phase.Due to the enhanced bonding force,the micro structure of the hot-dip coating of the Zn-5A1 alloy with rare earth elements is more compact and uniform than that without rare earth elements.The addition of rare earth elements improves the corrosion resistance of Zn-5A1 alloy coated steel wire.Due to the rare earth segregation,which prevents the corrosion of the grain boundary and enhances the anti-intergranular corrosion performance,steel wire exhibits the optimum corrosion resistance when the content of rare earth elements is 0.08 wt.%.