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Advice needed on steel prepping prior to painting

Posted by kudzu9 (My Page) on
Fri, Mar 6, 09 at 16:30

I've had an address sign made for my house from 1/4" steel plate, with the numbers laser cut out. I want to coat the sign with a commercial grade epoxy coating that I have, and want advice on prepping the surface. The steel is new and is not appreciably rusty, but it has that dark-brownish, oxidized surface appearance. I previously used this epoxy coating on a large steel structure that was sandblasted first before it was primed. But I don't have a sandblasting setup of my own, and I can't find anyone to do this small job at a reasonable price. What are my next best options for cleaning it up before I coat it?

Follow-Up Postings:

RE: Advice needed on steel prepping prior to painting

The brownish oxidized look of your steel is more than likely mill-scale. When steel is formed into sheet, bars, rod, etc... Most of the time, there is heat applied to the raw steel in order to form it into a finished product. This heat created the mill scale. You'll definitely want to remove that, as paint will simply peel off if you don't. Also, steel tends to be very smooth after the scale is removed, so you'll normally want to scar it a bit to get a paintable surface.

The only way that I know of to properly prep steel for paint without sandblasting is actually sanding on it by hand. Get a fairly heavy grit sandpaper (150 grit or so) to take off the scale, and a lighter grit (220ish) to roughen up your steel a bit.

Should work out ok for ya. Hope this helps.

RE: Advice needed on steel prepping prior to painting

Check the local High School. The machine shop at the HS near me has a sandblasting cabinet. I talked to the instructor and he had a student blast it for me. Charged me 5 dollars and everyone was happy. Never hurts to check.


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