Painting a radiator

Old 07-11-20, 09:52 AM
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Painting a radiator


I have large, old fashioned cast iron radiators in my house. They were all painted at some time or another, and I would like to repaint them. Most of the paint is in decent condition, but there are certainly a few chips and some flaking paint.

My radiators have a surface temperature of about 120 degrees in peak heating season. Is that too hot for a latex based paint? Are there particular primers and paints that I should use?

I have used the high temp rustoleum spray paint in the past and the results were mixed. And again, do I need to use high temp products given the peak temperature of the radiators?

Old 07-11-20, 01:04 PM
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Latex paints are not good, get them clean (sand blast) prime and paint with Rustoleum primers and paint and your good!
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Old 07-12-20, 03:14 AM
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I wouldn't trust latex paints on cast iron. Not sure how they would fare with the heat but latex has virtually no rust inhibitive properties and oil base dries to a harder finish than latex does. [will wear better]

While removing all the existing paint will produce the nicest looking job, it's normally acceptable to sand/scrape and repaint.
Old 07-12-20, 07:53 AM
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Sandblasting is definitely out of the question. Removing the radiators is near impossible, and I don't intend to sandblast inside the home.

I'll consider oil based. There really isn't a rust issue in places where the paint has chipped, but that doesn't mean oxidation isn't occurring, and a harder finish seems preferable for sure.
Old 07-12-20, 09:03 AM
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For what it's worth, I've had 50+ cast iron rads painted with standard indoor latex paint with no issues. The only prep was scraping to get any flaking paint off.

Mark is definitely the expert - and I'm sure oil-based paint is a better solution, but I haven't seen any issues with the reasonably low temperatures that hydronic systems get to. (Steam heat is probably a different story).

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