Q: We have an application where a cast iron component is exposed to a temperature of 560°C for approximately two hours. Is there a paint product available that can withstand this temperature without turning dull or blistering, and still offer good corrosion resistance?
A: Yes, there are powder coatings that can withstand 560°C for two hours and maintain coating integrity and corrosion resistance. This technology is based on silicone polymers and has been used for years on applications such as gas grills and exhaust parts. They are typically low in gloss to begin with and come in any color you like – as long as it’s black.
Essential to the performance of this technology is the cleaning and preparation of the metal. Conventional phosphate pretreatments unzip at these high service temperatures, causing total loss of adhesion. Chromates work, but may be a problem with handling and effluents. Blasting with clean media followed by a rinse and dry-off works quite well. Proper cleaning and surface preparation of the metal should give you at least 500 hours of salt spray resistance.