Introduction
High temperature coatings play a significant role in the protection of substrates from corrosion when they are operated on high temperature. Those high heat rated components not only helps in preservation of coating integrity during the extended operations, but also their special additives offer resistance to environmental activities such as cold shock, moisture and exposure to UV rays. High temperature coatings have a maximum temperature of around 1200 F.
Types of High Temperature Coatings
Following are the types of high temperature coatings:
- Epoxy Coatings: These are profoundly used in oilfields or petrochemical family appliances. These are the organic polymers obtained through chemical reactions between epoxy resins and co-reactants.
- Epoxy Phenolic Coatings: These are known as ambient cure which are obtained by the chemical reaction between epoxy resins and phenolic at the room temperature. This coating is used for immersion services, tank linings and brine immersion services.
- Epoxy Novolac Coatings: Novolac epoxies are typically heat resistant up to 350-360 F. There is a presence of aromaticity in its molecular structure. Epoxy novolac coatings can be used for applications such as tank linings.
- Silicone Coatings: It is obtained through pure or hybrid polymers. These are transparent to UV rays of sun. Pure silicone coatings are used for exhaust stacks, boilers and other steel surfaces.
- Multi-polymeric Matrix Coatings: These are either single or muti-component, organic and composed form of resin combinations. It usually consists of aluminium and micaceous iron oxide flake or titanium. These are used in various industries such as automobile industry, aerospace, marine, sports goods, electrical and many more.
Where are High Temperatures Coatings used?
High temperatures coatings are used in various appliances. Special high temperature coatings become a necessity for every industry as per their application and performance needs. Below mentioned is the list of appliances where high coating temperatures are used:
- Hearth
- Heating appliances such as barbeques and grill smokers
- Mufflers and exhaust systems used for working machines
- Aerospace propulsion structures
- Gas turbines, industrial furnaces and industrial silencers.
- Equipment that are mobile or installed and whose temperatures reach above 200 F.
High temperature coatings are also frequently used in various industries such as aerospace, military, petrochemical and power industries. Processing facilities such as power plants and petrochemical plants are one of the highest users of high temperature coatings.
Difference between High Temperature Coatings and Conventional Coatings
| High Temperature Coatings | Conventional Coatings |
| ● Can bear long-term exposure to high operating temperatures.
● Holds firm integrity and helps in protection from substrate contact with various environmental factors. ● Consists pigments that are not affected by heat. ● Holds on to substrates without flaking and pitting. |
● Consists of elements that starts melting in high temperatures as low as 200 F.
● Leads to damage of various factors such as fading of colour, loss of gloss, etc. on being exposed to high temperatures. ● Lead to Micro pitting: a form of fatigue failure. ● Micro pitting allows moisture to pierce the coating. |
How do high temperature coatings prevent corrosion?
Components such as Silicone resins and robust pigments have a capacity to remain stable even under the exposure of heat. Due to this strong characteristic, these substances are used in high temperature coatings. These coatings form a polymer shield around the metal which obstructs direct contact between the substrate and environmental factors. The silicone resins consist of silicon-oxygen bond also called siloxane bond or SI bond. This bond is approx. 25% stronger than carbon-carbon bond. This bond forms a cross-linked form. This formation guarantees heat, chemical and light degradation resistance. These factors help in increasing the durability of the coating and also prevents corrosion.
Advantages of Preheating Parts before Coating Temperature
SilcoTek’s coating in high temperature is used by many temperatures. SilcoTek suggests their costumers to preheat their parts in a stationary atmosphere to achieve quality coating performances under high temperatures. Pre heating of parts also help in getting all the carbon precipitation and averting the coating from being away from the stainless steel during its exposure to high temperatures.
Limitations of High Temperature Coatings
There are various temperature and performance limitations of high temperature coatings. High temperature coatings have naturally high hardness and brittleness which many of times leads to failure. Also, they are prone to integrity failure because of sudden fluctuations in the temperature. Usually, Chemists keeps a check on the characteristics of high temperatures coating during the performance through various methods such as adhesion and flexibility tests, durability and hardness tests, etc. They also organize quench test in which the heated coating is cooled down with the help of cold water if it is needed. These tests help in providing a better understanding and accuracy of the performance of coating to the costumer.
Also, maintenance of high temperature coating appliances is a tough task as abrasive blast cleaning is not possible. Thus, hand or power tool cleaning remains the only solution for surface preparation.
Take away
This is the brief explanation of getting better coating performances at high temperatures. We hope those tips will be effective for you. Please let us know through your valuable feedback and the suggestion in the drop box.