High temperature coating

high temperature coating

High temperature coating for heat protection

When a substrate is continuously subject to extreme temperatures, choosing a heat resistant coating is crucial.  High and low temperatures namely, damage some coatings, which leads to premature maintenance and naturally, brings unexpected costs along. The same happens if the substrate remain untreated. High temperature coating can save you the trouble of unplanned maintenance.

High temperature coatings have special properties which allow them to withstand extreme temperatures. The coatings are designed for challenging environments which require resistance to high or low temperatures; or where temperature fluctuates from one extreme to another.

Heat resistant coatings are sometimes divided into four groups being:

  • Heat reflecting coatings for roofing systems;
  • Fire prevention coatings;
  • High build insulation coatings;
  • Coatings that provide heat resistance during service.

In this article we focus on the two last groups. We’ll answer the FAQ’s about high temperature coatings and introduce the most common uses.

Advantages of high temperature coatings

The standard heat resistant coating systems have a design which can resist temperatures from 150 °C to over 760°C. There are however, also special, mostly industrial coatings for temperatures between -185 °C and 870°C. The high temperature coatings can be based on epoxies, silicon or multi polymer matrix resins; the composition of the coating is dependent on the level of heat resistance.

Heat protection is, nonetheless, not the only beneficial property of high temp coatings. They additionally protect the surface from corrosion and corrosion under insulation (CUI), and they prevent over heating and increase surface durability. These properties enable other advantages such as:

  • Higher operating temperatures which can lead to increase in efficiency
  • Insulation of various industrial components from prolonged heat loads
  • Reducing thermal fatigue and improving performance of machines for example
  • Increasing cost efficiency

High temperature coatings for steel and other metals

High temperature coating on metal pipe

Applying high temperature coating for metal pipe before insulation.

Heat resistant coatings are most often applied on steel and other ferrous metal surfaces, due to the fact that these metals are the most sensitive for faster erosion caused by temperature extremes or fluctuation.

Continuous exposure to high heat negatively affects untreated steel surfaces. Not only is the material in danger, but also the environment may suffer. High temp coating for metal and its alloys prevents oxidation of the material and contamination of working environment

Because of high temperatures, the steel surface…

  • …possibly releases toxic gases and chemicals into the air
  • …loses its capacity to carry heavy mechanical loads
  • …erodes faster

The high temperature coating for steel prevents these phenomena by blocking gas diffusion into and out of steel structures or metals, and by forming a barrier between the heat and the substrate.

Furthermore, applying heat resistant coating for metal enables effective heat treatment processes. High temperature coatings minimise oxidation and reduce surface defects on stainless steel and other metals. Consequently, they increase the durability of the surface.

Combating corrosion under insulation

Insulating steel structures is very common in industrial environments; it can either minimise heat gain or heat loss, it reduces costs and improves cost efficiency. It can additionally improve staff safety in working environments by insulating hot or cold items which might cause employee injuries.

Nonetheless, insulating steel also brings potential risks along in forms of deterioration of the surface under insulation. Corrosion under insulation (CUI) refers to the steel structure eroding under the insulation material, directly on the metal surface.

CUI is almost inevitable under insulation of steel work; the consequences may be disastrous if the corrosion is not discovered on time. Early detection is the best way of fighting CUI. However, the durability of steel surfaces under insulation can be extended by a high temperature coating with corrosion resistant coating.

Careful there! Not any coating is suitable for this purpose; the coating must be approved for use under insulation. It additionally must meet the requirements of the temperatures.

The CUI coatings are ideal for the extreme environment between the steel structure and insulation material; the area is often subject to extreme temperatures and eventually to water condense. For example the following products have special design for these environments.

  • International Intertherm 228
  • International Intertherm 751CSA
  • PPG Hi-Temp 1027

High temperature epoxy paint

Also non-insulated steel structures sometimes require a heat resistant coating due to the fact that extreme temperatures weaken the properties of steel. High temperature coatings for steel are most commonly epoxies or silicone systems.

The high temp epoxy coatings include epoxy novolac and phenolic which both are high cross linking.  Epoxies exists as medium high temperature resistant and high heat coatings. The suitable product is dependent on:

  • Environment of the steel structure;
  • Substrate material;
  • Temperature fluctuation;
  • Exposure to chemicals.

Ceramic coating for extremely high temperatures

High temperature ceramic coatings are ideal for preventing corrosion problems of for example engine components and exhaust systems. They are also non-conductive, hence they are suitable for use as insulation coatings. Very high temperature paint is usually a ceramic coating which can withstand temperatures up to 870°C .

Applications of ceramic coatings are possible on various metallic structures such as chrome, cast iron, aluminium etc. Due to the fact that these ceramic coatings reduce the surfaces’ heat content and detonation, they are ideal for:

  • Manifolds,
  • Brackets,
  • Exhaust pipes and headers.

These coatings are also helpful in extending the life of components; they provide reduction in thermal fatigue, decrease corrosion problems and provide lifetime protection against rust. Additionally, the parts with a high temperature ceramic coating cool down fast which makes it easier to adjust them.

Heat resistant powder coating

As many other coatings, also heat resistant metal paint exists as liquid paints and dry powders. The powders are usually on silicone basis:

  • Epoxy acrylic silicone (max operating temperature 300°C, peak at 350°C)
  • Acrylic silicone (max operating temperature 400°C, peak at 450°C)
  • 100% silicone (max operating temperature 500°C, peak at 550°C

The heat resistant powder coatings provide similar benefits to those of the liquid alternatives. The powder coat additionally guarantees a much tougher surface with extreme gloss and colour retention. Powder coatings are also more environmentally friendly than liquid paints due to the fact that they do not emit (or contain) any VOC (volatile organic compounds) which are in the solvents of some liquid paints.

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