Study On Quality Improvement Of Zinc Plating For Strip Steel

With the excellent protective performance of the galvanized layer,electrogalvanizing has long been an important technical means widely used in steel corrosion prevention.The thickness uniformity and color uniformity of the continuous electrogalvanized layer of the strip determine the protective effect of the steel to a large extent,and also affect the appearance of the strip.In order to improve the quality of galvanized layer and reduce the cost of galvanized layer,it is necessary to improve and upgrade the strip galvanizing technology to further improve the quality of galvanized strip.This paper mainly focuses on improving the quality of strip electrogalvanized layer and conducts the following studies:(1)In the process flow before electrogalvanizing,research and explore the pretreatment technology of iron flash plating of steel as a process that is beneficial to environmental protection and can effectively cover defects,and determine the formula of flash iron plating solution is 350g/L ferrous sulfate heptahydrate,25g/L sulfamic acid,85g/L sodium chloride,35g/L boric acid,100mg/L sodium dodecyl sulfate,the temperature of the plating solution is about 25 ℃,the current density is 10A/dm2,the composition of the plating solution and the process conditions of the flash iron plating solution has good dispersion ability,Covering capacity,can get a smooth and bright flash iron layer,strip steel after 10 s flash iron pretreatment and then electrogalvanizing,the surface zinc layer is more uniform and dense than the galvanized layer without flash plating pretreatment,no obvious defects,corrosion resistance is improved.The flash iron pretreatment process can effectively eliminate the surface defects of the matrix itself and greatly improve the surface quality of the electrogalvanized sheet.(2)In order to improve the uneven surface state of steel before electroplating and improve the good compatibility between the galvanized layer and the matrix,the pre-galvanized iron alloy process is studied and explored to improve the matrix-state before galvanizing.The formula of flash plating solution was determined to be 165g/L zinc sulfate heptahydrate,10g/L ferrous sulfate heptahydrate,40g/L potassium chloride,25g/L boric acid,30g/L sodium citrate;Process conditions: p H value is 4,temperature is about 25 ℃;Additives: 3g/L sodium benzoate,300mg/L niacin.The plating solution composition and process conditions have good dispersion ability and covering ability,can obtain a smooth and bright flash galvanized iron layer,level the strip matrix and eliminate surface defects to reduce its surface roughness,so that the brightness,flatness and corrosion resistance of the subsequent electrogalvanized layer are effectively improved.Compared with flash galvanized bath,flash galvanized iron plating solution has higher current efficiency,and the time required to obtain a flat and dense intermediate layer can be obtained by flash galvanized iron process in the same current density range.Research on high-speed electrogalvanizing technology for sulfate galvanizing.Through the study of high-speed electrogalvanizing of sulfate galvanizing solution,the composition of galvanizing solution was determined: 90g/L zinc ion,4g/L sulfuric acid,30g/L boric acid;Process conditions: the temperature is about 25 ℃;Additives:60mg/L sodium benzoate,50mg/L niacin and 4mg/L polyacrylamide,the plating solution formula and process conditions can be obtained by using high current density in a short time to obtain a brighter,flat and dense zinc layer,the addition of additives in the plating solution makes the deposited coating more fine,so that the coating corrosion resistance is better.