Stainless Steel Smokestack

Q. I am the technical manager at my plant. We produce sheet metal enclosures for various industries. We have an oil-fired steam boiler with a smokestack that needs to be replaced too often because of rusting. The stack reaches at least 200ºC during operation.

I want to replace the mild steel smoke stack on the steam boiler with one made from stainless steel. The new smokestack material is 3 mm thick. What treatment do you recommend I apply to keep the paint from peeling off? I heard it was hard to paint stainless steel. W.R.

 

A. Stainless steel is not hard to paint, but care must be taken in its pretreatment. First, you must degrease the stainless steel surface. Abrading the surface without degreasing could possibly spread the oily soils without removing them. Second, you must pretreat the surface by abrading using either a light sanding or an abrasive blast, since wash primers would not be able to withstand the operating temperature. Finally, you apply one of the high-temperature-resistant paints. These paints are used for painting stove pipes, gas grills, etc., and will work well on steam boiler smoke stacks. They are sold at paint stores, automotive parts stores, hardware stores and big box stores.