Study On Color Hot Dip Galvanizing Process And Coating Performance Of Iron Tower

Hot-dip galvanized iron tower is widely used in the field of transmission power grid construction because of its excellent corrosion resistance and good protection effect.The Tibet area is vast and the geomorphic environment varies greatly from north to south.The traditional hot-dip galvanized iron tower is a single bright metallic luster silver white,which is highly reflective and difficult to coordinate with the geomorphological environment of Tibet.In order to avoid damage to the natural environment of Tibet,the galvanized iron tower needs to be colored,and the organic coating angle steel is easy to age under long-term sunshine,and defects such as fading,chalking and foaming occur.In this paper,through systematic research on color hot-dip galvanizing process,the color elements of the galvanizing bath are optimized,and two color coatings of the target color are coordinated with the geomorphology of Tibet,and the structure of the plated parts,the composition of the galvanizing bath.The influence of process parameters on the color coating effect was studied.Then the influence of Mn amount and immersion temperature on the corrosion resistance of the coating was studied.The weathering comparison test between color coating and organic coating angle steel was carried out to analyze the microstructure of the color coating.The coloring mechanism of the coating was obtained,and the main conclusions were as follows:(1)The results show that Mn is suitable as a coloring element of color hot-dip galvanizing bath,and Zn-Mn alloy hot-dip galvanizing bath has more hue and high color saturation.The zinc bath can be recovered by adding not less than 0.011 wt.%of Al to the zinc bath.Increasing the amount of Mn and the zinc bath temperature can deepen the surface oxidation of the galvanized coating,increase the color saturation of the galvanized coating,and increase the surface temperature of the hot-dip galvanizing sample as the thickness of the galvanized coating increases.The rate of decline is slowed,the oxidation time of the galvanized coating is prolonged,and the color saturation is significantly improved.(2)The results show that for different thicknesses of hot-dip galvanized samples,by controlling the process parameters such as zinc composition,zinc bath temperature,immersion time and cooling method,the oxidation state of the surface of the coating is affecte,and finally the grass green and sandstone galvanized coating are obtained.(3)It is found that the corrosion resistance of color coating is closely related to the composition of the zinc bath.The addition of Mn in the zine bath can greatly improve the corrosion resistance of the coating,and the corrosion resistance increases with the increase of Mn amount.When the amount of Mn is 0.4 wt.%,the corrosion resistance of the galvanized coating is slightly lowered.In the same Mn amount,the corrosion resistance of the coating decreases remarkably with the increase of the immersion temperature.The main reason is that the higher immersion temperature promotes the rapid growth of each phase in the coating,and the structure becomes looser,which provides a path for charge transfer in the coating,accelerating the corrosion process in the coating.(4)The accelerated aging test found that the color aging resistance and high temperature aging resistance of the color coating were stronger than that of the organic coating.The color galvanized angle steel and the organic coated angle steel were heated at 168 h and 120? for 96 h in the UVA section.The color coating does not fade,and there are no defects such as obvious pores,and the organic coating is obviously faded,and a large number of defects such as pores appear.(5)The research shows that the color coating structure is similar to that of the traditional coating.It consists mainly of ? phase,? phase and ? phase alloy phase.The ? phase is densely fenced,and the ? phase has long column and short.In the form of two bars,the outermost layer of the coating is mainly the ? phase formed by cooling and solidification.In the color coating,Mn is enriched on the surface of the coating,and a layer of Mn-containing oxide is formed on the surface of the coating.The Mn-containing oxide is mainly composed of MnO and MnO2,while the conventional silver-white galvanized surface does not contain Mn oxide,mainly ZnO and yttrium,?-FeZn13 phase,so the color plating is mainly colored because the Mn-containing oxide on the surface of the coating causes interference of light on the surface of the coating,so that the coating exhibits multiple colors.