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The coating used in precision casting is primarily composed of silica sol.
Release date:
Nov 14,2025
Abstract
Silica sol primarily consists of silica, high-density substances, sodium dioxide, pH-adjusting agents, rheological modifiers, colloidal particles, and more. The physicochemical properties of these components significantly influence the strength of precision-cast shells and the stability of the coating.
Since it is challenging for precision casting manufacturers to detect these physical and chemical parameters, it is essential to strengthen supplier selection, evaluation, and verification processes. Additionally, different specifications of silica sol should be used for the surface and back sides—specifically, S-830 silica sol for the surface layer and S-1430 silica sol for the back side. In precision casting production, the method used to prepare the coating directly affects the quality of the final castings.
The preparation of the coating typically begins by adding silica sol, followed by a wetting agent. Next, refractory powder is incorporated during mixing, and finally, a defoaming agent is added. To ensure high-quality coating application, all surface coatings must use entirely new materials; the mixture should be stirred for more than 24 hours before use. However, if only partial new ingredients are being added, the stirring time can be reduced to as little as 12 hours. For transition and subsequent layers, the mixing time for the coating can be even shorter than that of the surface coat—again, provided the materials are entirely fresh. In such cases, the stirring time may still exceed 12 hours. If the prepared coating isn’t used immediately, it should be capped tightly to prevent moisture evaporation.
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