How Do High Temperature Powder Coatings For Exhaust Systems Work?

FORREST Senior Research Chemist Dr. Sasha Tavenner Kruger, Ph.D. explains in Powder Coated Tough Magazine

Powder Coated Tough called on FORREST Technical Coatings Coatings Research Chemist Dr. Sasha Tavenner Kruger, Ph.D. to write a feature article for their July 2020 extreme temperature powder coatings issue about high temperature powder coatings for motorized vehicle exhaust systems. 

High heat paint and high heat powder coatings used as exhaust paint lends corrosion resistance to the exhaust systems of recreational vehicles like ATVs, motorcycles, automobiles, and snowmobiles. While not covered in this article, the high temperature exhaust paint mentioned also plays a crucial role in corrosion prevention for the mufflers and exhaust parts of working vehicles such as farm equipment and agricultural equipment. 

Whether for work or play, these extreme vehicular machines operate at continuous extreme high temperatures in high impact environments. These high heat environments test the adherence, flexibility, impact resistance, heat resistance, and corrosion resistance of exhaust paint daily.  Dr. Tavenner Kruger explains the choices of high heat resistant resins, heat resistant pigments, and other additives that a chemist uses to achieve flexibility, corrosion resistance, and adhesion and film integrity throughout continuous high heat exposure and frequent quench cycles. To quote the chemist from the article:

When silicone-based coatings cure, they tend to form very highly cross-linked structures. These types of structures are generally very hard, chemical resistant, heat resistant, weathering resistant, and light-degradation resistant. This leads to better maintenance of gloss with light exposure than most alternative organic coatings. Electrical insulative properties are another aspect of silicone-based coatings.

A trade-off with high-hardness coatings is brittleness, especially when shocked with an impact or very rapid temperature change. Those cured coatings with the highest cross-link density are the most sensitive to thermal shock and are the least flexible. Rapid changes in temperature and traveling in highly abrasive landscapes is to be expected for motorized vehicles. As they were designed for this purpose, the manufacturers and users of these vehicles expect all parts to be up to the challenge. Since the cross-linking structure of high temperature resins tends towards brittleness, the coatings chemist must formulate to minimize undesired effects. Very high molecular weight resins can provide a very hard yet tough coating that is crack resistant. However, this new technology is just beginning to enter the market.

Read the full article on Powder Coated Tough's website or in the full digital edition of the July Issue here.