Although not a coating in the sense of the other technologies covered in this article, thermal history paint (THP) is worth highlighting.

This novel technology has been successfully used to measure the temperature profile in many industrial applications, including turbochargers, automotive valves, and pistons. In a piston application, the technology can acquire full temperature profiles to provide a unique insight into thermal conditions, which can be used to validate simulations and improve the piston design.

THP consists of two main components – paints and a read-out device. The paint, which contains luminescent pigments, is applied to the surface of interest. When the component is heated during operation, the luminescence pigments change irreversibly. After cooling down, the read-out device, using laser-introduced luminescence, can detect the changes in the pigments and correlate them to a temperature using a predetermined calibration curve.