Study On Technology Of Non-pickling Hot-dip Galvanizing

Traditional hot-dip galvanizing process is a cost-effective anti-corrosion technology,but there are many drawbacks of traditional hot-dip galvanizing,such as its waste acid pickling stage,waste water,waste gas serious impact on the survival of our environment.Shot blasting pre-treatment process instead of pickling rust treatment process can be resolved before the pre-treatment phase contamination problem fundamentally.Shot blasting process with high efficiency,strong cleaning ability,refinement advantages steel substrate surface of the grain,etc,but there is not yet mature shot blasting hot dip galvanizing process.In this paper,the more comprehensive and systematic study of the hot-dip galvanizing process shot blasting,shot blasting and hot dip galvanized coating chalking resistance and corrosion resistance are studied.It was found that the shot blasting efficiency was the highest when the diameter of the steel shot was 0.8 mm,and the surface roughness of the steel base was significantly increased,which was 5¹0 times of the surface roughness of the steel base after pickling and rusting;And the grain size of the steel-based surface decreases with the increase of the diameter of the steel pellets.The wetting performance of the steel-based surface increases with the increase of the shot-off time.The best technological parameters of shot blasting were determined as follows:shot blasting time 20 min,steel ball diameter 0.8 mm,dip plating temperature 450?,dip plating time 40 s.The surface of the steel substrate after the shot blasting and depression will affect the alloy phase growth morphology.The protrusion is easy to form?phase,was"outbreak"state,depression is easy to generate?phase.The thickness of the steel layer decreases with the increase of the diameter of the steel ball.The grain size of the steel base decreases with the increase of the diameter of the steel ball.The quality of the coating increases with the diameter of the steel ball in the range of 0.2⁰.6 mm,The results show that the coating thickness decreases with the shot age of 20⁴0 min,and the thickness of the coating decreases with the shot loss time of more than 40 min.With the extension of the shot blasting time,The surface roughness of the steel base gradually increased and stabilized.The grain size of the steel base surface decreased at 20⁴0 min,and reached the minimum at 40 min.After 40 min,the grain size of the steel surface increased.The thickness of the coating is 10³0s,the thickness of the coating is decreasing,and the thickness of the coating increases after 30 s.With the extension of the plating time,the quality of the coating is getting better and better,and the optimum temperature is 40 s.When the plating temperature is 430⁴50?.The thickness of the coating decreases,and the coating thickness increases when the dip coating temperature is higher than 450?.When the dip coating temperature is 430⁴50?,the quality of the coating becomes better and the quality of the coating is optimized after the dip temperature is higher than 450?.Shot blasting hot galvanized coating has a good anti-chalking properties,the coating adhesion is higher than the traditional pickling hot galvanized coating.?FeZn21?,which is extended from the?phase?FeZn21?to the surface of the coating,which eventually leads to the dissolution of the coating.The cracked pyrolysis hot-dip coating cracks originate from the?phase?FeZn₇?,?phase(FeZn₂₁)and steel-based surface bonding strength,from the?phase extends to the coating surface,the coating will not fall off.The corrosion resistance of the two processes is about the same,and the corrosion of the coating is developed from intergranular corrosion to uniform corrosion.With the prolongation of the corrosion time,Zn has complicated chemical reaction,first Zn?OH?₂,Zn in the process of the final formation of complex basic salt material Zn5?OH?8Cl2.