Preparing Porcelain Enamel for application

There is much effort and technology incorporated in preparing Porcelain Enamel, prior to application to the steel surface of boilers. Processing steps include production of Porcelain Enamel frits and milling of the frits both for wet and powder application. Frits are produced by certain specialized manufacturers who also usually supply the specially treated Porcelain Enamel powders, ready for dry electrostatic application.

For the mostly used wet application Porcelain Enamel is normally supplied as combination of frits to be wet milled in ball mills at customer's shop. The frits are normally formulated into a mill batch with addition of water and other solid materials such as silica, clay and electrolytes (to obtain proper dispersion in water and flow characteristics of the slip). Typical mill addition for 100 kg of frits consist of 15 to 25 kg quarts, 6-8 kg clay, 0,25 kg borax, 0,15 kg sodium nitrite.

After milling with water to the required fineness and specific gravity, Porcelain Enamel "slip" is normally transferred to a storage tank equipped with a stirrer and let through a sieve with the appropriate mesh before going to the application.
Frit manufacturers can supply on request bigger bags containing the already weighed "mix" of solid components of the batch to be milled with water.
Also dry milled enamel powders ready for wet application can be supplied which do not need to be milled any more, but only to be dissolved in a mixer with the prescribed quantity of water.