Two-Coat-One-Fire Enameling System
Release time:
2026-05-29 11:26
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The development of the pickling-free bonding ground coat and the two-coat-one-fire enamel frit in 1980 was the first breakthrough in enamel technology. This process not only broadened the range of steel plates used for enamel but also resulted in excellent adhesion after firing. Compared with the three-coat-two-fire and two-coat-two-fire processes, this process saves energy (one firing replaces two), reduces costs, and will achieve a high degree of automation. To date, the two-coat-one-fire enamel system has developed rapidly, including the following three processes:
(1) Wet-to-wet process
(2) Dry-to-dry process
(3) Wet-to-dry process
Wet-to-Wet Enameling
A ground coat enamel slurry containing an adhesive is applied by spraying and dipping, followed by a short drying time before the cover coat is sprayed on. This method can also be applied to automated processes such as electrostatic spraying and dipping.
Advantages of the Wet-to-Wet Enameling Process:
(1) Requires the use of enamel grade steel plates.
(2) No air conditioning is required in the spray booth.
(3)There are no restrictions on the color of the cover coat(except for the two-coating-one-firing electrostatic enamel coating process). The wet-to-wet enameling system is the only one of the three two-coating-one-firing enamel coating methods suitable for coloring porcelain enamelware. Therefore, if the trend is to increase color and reduce whiteness, the wet-to-wet enamel system will become even more effective.
(4) Except for vertical enameling, the wet-to-wet enameling system is suitable for enamelware requiring horizontal enameling, such as bathtubs and water spray tanks in the sanitary industry.
(5) Compared to other two-coating-one-firing systems, the wet-to-wet system requires almost no additional investment. For example, for the sides of drinking vessels... For enamel coating, the wet-to-wet process is easily considered because the parts are not particularly complex and will not cause problems.
(6) Compared with the other two enamel coating processes, the wet-to-wet process system is suitable for small-batch production.
Disadvantages of the wet-to-wet system:
(1) For complex parts, care must be taken not to spray the ground coat too dry, otherwise capillary action will occur between the cover coat and the ground coat, causing small cracks during firing.
(2) If the ground coat is applied too thickly, small cracks or island-like protrusions may occur during firing. The ground coat thickness should generally be 30-70 μm.
(3) When using a two-coat-one-fire system, if the ground coat thickness is too large, boiling will occur during firing, causing defects on the surface of the cover coat. For example, this phenomenon is easily caused when applying the ground coat using electrostatic methods on the edge of the vessel due to edge adsorption.
(4) If the ground coat is too dry before applying the cover coat, capillary action will cause cracks in the cover coat during firing.
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