Issues with rust-proof paint for high-temperature pipelines

1) Insulated pipes: Epoxy zinc-rich primer is generally used when the temperature is ≤80 degrees, while inorganic zinc silicate primer is typically used for temperatures between 81 and 400 degrees. Generally, two coats are applied, that is, two layers. 2) For buried pipes, an epoxy coal tar paint suitable for winter conditions is usually used as the primer. The painting sequence is: primer – topcoat – glass cloth – topcoat – glass cloth – two layers of topcoat. 3) A layer of winter-type epoxy coal tar pitch coating is generally also applied as the primer for cold-insulation pipes; refer to SH3022 for specific specifications.

Shouldn’t this standard be used as a general standard for industrial pipelines? I mean, are there any regulations in national standards or codes related to pressure pipelines regarding this matter?

For areas that need to maintain high temperatures, I believe the purpose of applying paint is mainly to prevent corrosion of the steel surface when the pipes are exposed to low temperatures during maintenance periods when the equipment is shut down. Therefore, standards generally require that insulated pipes also be coated with anti-rust paint. SH/T 3022-2011, \"Design Code for Corrosion Protection Coatings on Petrochemical Equipment and Pipes,\" is a commonly used coating standard in the petrochemical industry; it is widely applied. It seems that there is no similar standard in national regulations. According to SH/T3022, there are corresponding painting systems available for temperatures below 600°C; therefore, insulation pipes at this temperature are generally painted. The question posed by the original poster is: “At what temperature do high-temperature pipes not require an anti-rust primer?” ”It seems there’s no regulation specifying this.

It can also be used as an insulating coating for corrosion protection and insulation – all achieved with just one layer of coating! The material selection depends on the specific operating conditions

Paint is used to prevent the insulation material from corroding it due to moisture

Applying anti-corrosion paint to pipes is intended for carbon steel pipes and low-temperature steel; anti-corrosion paint needs to be applied regardless of the temperature. In cases where high temperatures exist and insulation is required, only anti-corrosion paint is applied. The types of materials used for the anti-corrosion primer differ depending on whether insulation is needed or not for the carbon steel pipes. No standard specifies a certain temperature threshold above which it is not necessary to apply an anti-corrosion primer

Generally, pipes need to be coated with an anti-corrosion primer

Check CJJ34, P51 by yourself. Steam pipes that are in continuous operation do not need to be coated.

The steam pipes are made of carbon steel; per the design requirements, only rust removal and application of an undercoat are carried out, with no topcoat applied. After that, insulation is added. For carbon steel pipes that are exposed to high temperatures, it is also possible, based on practical experience, to omit anti-corrosion measures, as the anti-corrosion coating would be burned off quickly, serving no purpose and instead resulting in a waste of investment.

The steam pipes in ordinary power plants are not painted for the following reasons: Ordinary paints can withstand temperatures of no more than 150°C; at such high temperatures, the paint can easily catch fire. Even if it does not burn, it will carbonize. Therefore, if there is indeed a need, paints that can resist high temperatures can be used. But steel at temperatures above 150°C, around that temperature I guess! Sometimes, when the temperature exceeds 100°C, bluing or blackening occurs; this is due to the formation of a dense oxide film of iron tetraoxide on the surface, which prevents further corrosion of the steel. Therefore, ordinary high-temperature steam pipes do not require painting. There are also negative aspects to this; when the temperature fluctuates around 150°C, corrosion can occur in steel as well, but the corrosion is not severe.