How To Clean Raw Steel Before Painting

billybob

Posted 3/9/2013 08:27 (#2952513)
Subject: How to prepair steel for painting??

Deshler, Nebr. 68340

I want to buy some raw steel from a local supplier. The steel comes oily and dirty. I can understand the importance for keeping the steel oily. Now how do I clean up this steel so I can get my primer to stick to the steel? In the past I have just washed it with gasoline and painted. Looks good at first, but over the years it will start to flake off. I am guessing it was because my steel was not prepared properly in the first place.

Do I just need to clean with gasoline and let it set out in the rain for a few months ? Sand it down and paint.

dakotadirt

Posted 3/9/2013 08:33 (#2952521 - in reply to #2952513)
Subject: Re: How to prepair steel for painting??

theres all sorts of metal prep product, basisly paint thinners. spray or wipe it down. krantz

Posted 3/9/2013 08:56 (#2952578 - in reply to #2952513)
Subject: Re: How to prepair steel for painting??

Hot water pressure wash it, let it dry, then a little sand blasting with a fine media. SaddleSore

Posted 3/9/2013 08:56 (#2952580 - in reply to #2952513)
Subject: Re: How to prepair steel for painting??

Central Ky.

Check out these sites, they've got metal prep products, but can't say how well they work.

www.kbs-coatings.com
www.por15.com
www.gobobpipe.com

ccjersey

Posted 3/9/2013 08:57 (#2952582 - in reply to #2952513)
Subject: Re: How to prepair steel for painting??

Faunsdale, AL

Unless you['re using ether or acetone and lots of it, there will still be a film of oil on the surface when you're through cleaning the oil off. I would pressure wash with detergent and then use an acid prep solution. Used to have one called Ospho. It was mostly phosphoric acid and would convert minor rust to iron phosphate I believe it is. Only needed to let it dry before painting, but usually left it overnight at least.

Have heard of a manufacturer leaving finished grain buggies and seed tenders out to weather for a few months before bringing them in and painting. Probably not much of an option for most people.

Ed Boysun

Posted 3/9/2013 09:13 (#2952623 - in reply to #2952582)
Subject: Re: How to prepair steel for painting??

Agent Orange: Friendly fire that keeps on burning.

I use a solution of 5% phosphoric acid in RO water that I usually keep mixed up in my 1 gal hand lawn & garden weed sprayer. Clean all the grease off and wet the surface of the steel. Will usually dry with a grey to black coating on the steel. When it's dry, apply spray paint.

steve c-il

Posted 3/9/2013 09:27 (#2952657 - in reply to #2952623)
Subject: Re: How to prepair steel for painting??

Central Illinois

Agree on the phosphoric acid. A "mild" solution is sold at most farm supply stores as Milk stone remover for milking equipment. Use it to treat the inside of metal fuel tanks on older equipment also. Steve nsfarm

Posted 3/9/2013 09:51 (#2952698 - in reply to #2952513)
Subject: Re: How to prepair steel for painting??

Manitoba, Canada

brake cleaner works good if its a smaller project Ben D, N CA

Posted 3/9/2013 09:56 (#2952707 - in reply to #2952513)
Subject: RE: How to prepair steel for painting??

Whiskey, Tango, Foxtrot

If there is any real heavy, scaled rust, I'll knock it off before welding. Otherwise when your all done building, pressure wash it several times so all the oil is gone. You actually want a good surface rust. Then spray it down with Ospho or Jasco Prep and Prime. Good stuff, both of them. Turns the surface rust into a black coating that is supposedly better than primer, right or wrong I still prime it. Then paint.

Sandblasting to white steel is best, but just not feasible for me. The phosphoric acid treatments seem to work really well.

bigmiker

Posted 3/9/2013 10:00 (#2952714 - in reply to #2952513)
Subject: Re: How to prepair steel for painting??

SW Ontario

If there is a lot of oil, then hot pressure washing would be a good first step. After its dry, use a good surface prep product. Our local body shop supply atore has two, surface prep and wax, oil, and grease remover. Though i cant recall the brand right now. This is the most important step, you wet a rag with some and wipe the area down. Once the rag is dirty, you find a clean spot and repeat. This will remove any remaining contaminants such as grease, dust, or even oils from your hand. Once you get these contaminants off the metal, a good primer and paint application should last a long time. Lizton farmer

Posted 3/9/2013 11:19 (#2952840 - in reply to #2952513)
Subject: Re: How to prepair steel for painting??

lizton IN

The kind of paint you use makes a big difference also. I have had good luck with rust oleum for most projects. I have had some cheep paint that didn't work well at all. pupdaddy12003

Posted 3/9/2013 12:16 (#2952922 - in reply to #2952840)
Subject: Re: How to prepair steel for painting??

NW Central Ohio

...I think your problem is mill scale...and I've done most everything to get it off. The best is an initial sandblasting...next would be washing down with grease remover (One that contains sodium hydroxide) and then soaking the metal in acid (Phosphoric or even Muriatic for a short time). Then you have to neutralize the acid with a base like baking soda..or a hydrated lime solution in water. You have to paint it immediately too...because once you clean it with acid..it's so clean it rusts in about 20 minutes. twraska

Posted 3/9/2013 21:28 (#2953945 - in reply to #2952513)
Subject: RE: How to prepair steel for painting??

Wallis, TX

Purple Power or one of its knockoffs sprayed on straight and pressure washed off, will cut the grease and oil. Sand blasting is about the only way to get the mill scale and even that is a chore. Some tanks are just left to rust for a year, then blasted and painted.