Function of Milling Additives for Enamel
Milling additives is very important part for porcelain enamel coating. There’re mainly four key materials to be used as milling additives for enamel coating. They are: Clay, Quartz, Sodium Nitrite and Borax. So what’s their function? Nolifrit will give your answer:
1, Clay
The main function of clay is to make enamel slurry of suspension property, enhance the mechanical strength of dry powder body, at the same time expand the firing temperature range of enamel frit.
The usage amount of clay for daily enamel ground coat and cover coat is about 6-8 for every 100 enamel frit(weight ratio). Transparent frit about 5-6.5, industrial acid resistant ground coat will need about 10, industrial cover coat about 3-3.5, there is no clay needed for cast iron cover coat.
Impurities contains in clay will affect its quality. For example, organics will bring bubbles, pores and black dots defects on enamel surface. Iron oxide will make titanium white cover coat become yellowish so reduce its whiteness. For acid resistant blue enamel cover coat Impurities contains in clay will make SiO2 and Al2O3 contents changed, then affect its acid resistance feature.
When Clay is over used, it will make enamel surface rough, reduce its glossy and acid resistance feature.
Hunan Noli Enamel Co., Ltd can supply high quality enamel clay. It’s all imported from one of the most professional clay manufacturer Müllenbach & Thewald GmbH, Germany. We are their agency of in China. Their MT-500/E,510/E,530/E series is especially designed for enamel coating, which has very good dispersibility and pausibility, which need less water in milling process.
2, Quartz
Only used in ground coat, using amount about 5-10. It will make enamel frit with higher fire-resistance and enhance chemical and thermal stability of enamel slurry.
We can produce 5,000 MT quartz powder every year, with very stable quality and competitive price.
3, Sodium Nitrite
Usually applied in ground coat, using amount is about 0.2-0.5(weight ratio). Main function is to prevent the rusty spot after enameling. It can also stop flow. But when over used, it will make firing temperature range of enamel frit become narrow, then boiling will happen when firing.
4, Borax
Mainly used in ground coat, using amount is about 0.5. It can prevent rust, decrease burned spot. Over using will cause boiling or burning when firing.