Under what circumstances is the intermediate coat of anti-corrosion paint applied?
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In anti-corrosion coating, generally, pipelines that are not insulated (and not made of stainless steel) require a primer and a topcoat; however, sometimes an intermediate coat is also applied. When calculating the amount of paint needed, it is specified that when the temperature is 120 degrees or less, a primer, an intermediate coat, and a topcoat are required, while when the temperature is above 120 degrees, only a primer and a topcoat are necessary. I would like to know what the function of the intermediate coat is, and whether it is directly related to temperature.
When the temperature is above 120 degrees, moisture is less likely to accumulate on the surface of steel structures, and moisture is an important factor that contributes to corrosion. In other words, at high temperatures, the corrosion rate decreases, so it is not necessary to use an intermediate coating; a thinner coating will also be sufficient. For corrosion at room temperature, an intermediate coat can increase the coating thickness and extend its anti-corrosion lifespan.
The anti-corrosion treatment on the outside of pipes requires a certain thickness of paint; generally, we apply only a primer and a topcoat, ensuring that the dry film thickness meets the specified requirements
At high temperatures, it can be thinner – it’s only used as a primer and topcoat, as long as the appropriate thickness is achieved. Typically, paint cannot be applied in very thick layers at once; that’s why intermediate layers are necessary. If the base layer can be applied thickly, then an intermediate layer isn’t needed even when not using high temperatures.
The function of the intermediate coat is to serve as a link between the layers above and below it