Most of us have heard of ceramic-coated headers and other exhaust components, but do you really understand what it is, how it’s applied, or how it works? Thanks to the Australian magazine FullBoost and Race Coatings, we get an inside look at both the process of coating various parts, and how the coating itself works.
The basic principle of ceramic coatings is thermal control. The coating itself acts as a barrier preventing the transfer of heat from one area to another. In the case of exhaust manifolds, the heat is trapped in the header, increasing exhaust flow efficiency, while keeping excess heat out of the engine bay.
Starting with headers, Ryan Parsons from Race Coatings walks the viewer through the process of preparation and application, which is similar regardless of the part being coated. Like any spray-on coating, be it rattle-can spray paint to these industrial-strength ceramics, surface preparation is key.
“Baking the parts in an over removes any kind of oils or solvents on the surface,” says Parsons.
Once the surfaces are clean, the items are sent to the sandblasting department to minimize any surface imperfections, remove any scale or loose debris, and to give the surface some “tooth” for the coating to adhere too.
The coating is then applied with an airbrush to the desired areas of the component, which is both inside and outside the tubes flanges in the case of the header in the video. By using an airbrush, not only is the application more controlled, but the thickness of the coating is kept to a minimum.
“The coating is so thin, that the entire object can be sprayed, including the gasket surface and bolt holes of the headers,” says Parsons.
Parsons then arranges a demonstration of how the thermal barrier provided by the coating affects pistons. Using three pistons—one uncoated, one coated with their “Premium Gold” coating and one with the “Premium Turbo” coating—a torch is applied to the crown and the temperature measured on the underside of the piston.
At a crown temperature of 81-degrees Celsius (177-degrees Fahrenheit), the underside of the piston measured 232°C (450°F). The “Turbo Ceramic” coating saw a crown temperature of 75°C (167°F) and an underside temperature of only 57°C (135°F). Performing the best of all was the “Premium Gold” coating, which saw a crown temperature of 85°C (185°F) only translate to an underside temperature of 50°C (122°F).
“What’s happening is, as we are heating the piston crowns with the torch, the heat energy is being dispersed throughout the piston and then into the crankcase. The ceramic barrier prevents the heat transfer into crankcase,” Parsons says.
The advantages of keeping the heat of combustion in the cylinder and not letting it spill into the wrist pin, connecting rod, and beyond are obvious, but in addition to heat-resistant coatings, there are also sprayable wear and friction-resistant coatings that a piston can benefit from. While the exact makeup of the coatings are closely protected industry secrets, this video provides a cool look into the application processes and capabilities of ceramic coatings.