Study On Preparation And Properties Of Acid-resistant Enamel Coating

Weathering steels are often used in harsh working environments,for example,in air preheaters which are exposed to high temperatures and acid gas corrosion.While the enamel coating has excellent high temperature resistance and corrosion resistance,so the application of enamel coating to the surface protection of weathering steel has become one of the hottest topics.Usually,the weather-resistant steel contains some alloy elements added to improve corrosion resistance,which is not conducive to the adhesion of the enamel coating to the substrate.Compared the enamel glass produced by Shandong Qiquan Company and other manufacturers,enamel coating with excellent acid resistance,impact resistance,and temperature change resistance was developed in this study.The physicochemical properties of enamel coating are mainly related to the sintering process and the amount of components.Enamel coating with smooth surface and a certain gloss was prepared by adjusting the enamel formula whose sintering temperature ranged from 930 to 950°C.Increasing the content of Li2 O and reducing the content of SiO₂ were selected to reduce the sintering temperature and improve the compatibility of enamel coating and substrate,the results showed that when the addition of Li2 O was 2.0wt.%,the sintering temperature decreased to 890°C,the high-temperature viscosity was decreased so the diffusion between the enamel coating and substrate was enhanced,and the impact strength was improved;Li2O promoted the phase separation of enamel glass,so as to improve the delicateness of the porcelain layer and the flatness of the porcelain surface;reduce the SiO₂ content increased the thermal expansion coefficient of the enamel,improving the compatibility of the enamel and the substrate.When the content of Li2 O increased from 0.4 wt.% to 2.0 wt.%,the acid corrosion of enamel coating decreased from 20.83 g/m2 to 9.47 g/m2,the shock temperature increases from 375°C to 425°C,and the impact strength increased from 13000 g.cm increased to 16000 g.cm.ZrO₂ is often used to improve the stability and performance of the material,However,excessive addition can easily lead to high sintering temperature and increase the high-temperature viscosity.Therefore,choosing a suitable amount of addition has positive significance for improving the performance of enamel coating.The results revealed that quality score of ZrO₂ less than 1% increased significantly the structural stability,volume density,oxygen atomic packing density and acid resistence with the increasing of ZrO₂ content.As the quality score of ZrO₂ was more than 1%,the surface defects increased,the structural stability and acid resistence became bad with the increasing of ZrO₂ content.The better properties and dense microstructure were obtained in the enamel coating doped with 1% ZrO₂ which showed the maximum acid resistence（4.72 g/m2）.So the proper ZrO₂ addition could improve the network structure and denseness,thus significantly improving acid resistence of the enamel coating.CeO₂ is generally used as clarifying agent in the glass composition,which can reduce the high-temperature viscosity of the glass melt.Therefore,an appropriate doping amount was selected to improve the densification of the enamel coating.The experimental results showed that the addition of CeO₂ reduced the glass transition temperatur,the surface was smoother more delicate;the addition of CeO₂ reduced the viscosity of the enamel melt,which enhanced the diffusion between enamel coating and substrate,so its impact strength had been significantly improved;CeO₂ has little effect on the linear expansion coefficient of the enamel.When the CeO₂ doping content is 0.8%-1.2%,the enamel coating showed maximum acid resisitence（3.14g/m2）;the enamel coating showed the maximum impact strength（23500g.cm）when the CeO₂ doping content is 1.6wt.%...