View Full Version : Paint recommendation for rusted steel?
Hello all. I am in the process of sandblasting some metal frames that are mostly still gavanized but, in some sections, the metal is going to be bare. Any suggestions for paint in those areas? No the metal cannot come out (easily) and it will have to be treated where it is for now.
11-13-2007, 05:56 PM
Personally, I'd say red lead primer if you can get it, and Rustoleum oil-based paint over that. Without more info, hard to guess as to the planned use and saltwater exposure.
11-13-2007, 06:24 PM
JFH, Just in case , bead blasting is much easier on the metal frames and will remove unwanted paint etc. as well as sand. I'd look to an epoxy primer or Rustoleum has a metal primer as well, paint with epoxy paint or as said above Rustoleum paint. Rustoleum does make a marine version of their paint which you can find in the big box stores, sometimes.
11-13-2007, 06:28 PM
Brand names like Ospho, Naval Jelly, etc.
I recall Rustoleoun is paint with a phosphoric acid component?
This acid converts rust into a stable compound which prevents formation of more rust, and makes a good base for oil base paint.
11-13-2007, 06:35 PM
Galvanizing Coatings Offering protection that's comparable to hot-dip galvanizing, these zinc-rich coatings keep your iron and steel surfaces free from rust and corrosion. All are solvent based and can be used in well-ventilated indoor, as well as outdoor, applications. Apply with a brush, roller, or sprayer. Parts can even be dipped. VOC compliant in all 50 states.
Cold Galvanizing Coatings— These coatings contain 93% of pure zinc. They meet MIL-P-21035 and are USDA accepted.
11-13-2007, 07:52 PM
(a) degrease: (soap and water works)
(b) convert rust to some thing inert: phosphoric acid treatment (Ospho , etc)
Old fashioned method on board ships is chip, wash, ospho, penatrol, then paint over.
I use Ospho, Porter 'U-Prime # 286' Fast Dry Universal Primer, and 2-part epoxy but the degease, ospho,penatrol and rustoleum route is pretty good.
11-13-2007, 08:34 PM
check this out - it's like rustoleum on steroids!
11-13-2007, 10:08 PM
I welded up a motor mount from stock steel at the big box store. I then used an angle grinder to get the mill scale off. I applied Zinga (www.zinga.com). Then I sprayed with Rustoleum. It has held up for a year's worth of occasional use in both fresh and salt water. I think this type of finish would work on your frames.
Just as a reference I painted some zinga on a piece of steel that I left outside for a year. The part that wasn't painted was considerably rusted. The part that was painted was ok.
Note that I don't own any interest or stock in the product - just that I've used it and it works.
11-13-2007, 10:19 PM
Mil spec. liquid galvanize-Devcon-Z
11-14-2007, 12:56 AM
I've had successes and failures with POR-15 and when it fails its ugly - it peels off in sheets. That said, I just bought some more of their Metal Prep - which I will used before applying epoxy paint.
11-14-2007, 03:13 AM
Ian, where do you get POR-15 over here ?
11-14-2007, 03:16 AM
If I was painting the metal I would want more info ... about every aspect of the intended use/s.
Sand blasting is radical, it gives fantastic results and is worth every cent.
When you are putting the primer onto blasted metal, get the thinning just right, fill the micro pores ... what you decide to apply must fill the pores in the surface and not be blowing bubbles 15 minutes after applying. Thin your primer really well. Don't just put straight unthinned primer on, air from the caves will blow bubbles in the coating well after you have finished painting and you will not actually be doing the job that you thought you were if you have pinholes inthe paint.
If what you are painting is going into salt, let the emulsions cure well, you will double the life of the primer and the paint.
If what you are intending to paint is to be alternated from salt and fresh, double check that the primer that you choose is suitable for immersion in both.
11-14-2007, 03:20 AM
Ian, where do you get POR-15 over here ?
Also available at a few resellers around Sydney too - eg VG Autopaints
I repainted my Detroits with it back in 2001 - and it worked rather well. you have to be careful not to get it on your skin because it stains rather badly - but back then I had a 30mm stainless pin holding my pinkie back together (I broke the last 1/2" off), so I couldn't wear a glove. My hand therapist was horriefied when I went in with this hand that looked like I'd been eating black mulberries - I think I'm immortalised somewhere - she took "industrial staining" photos for her lecturing duties.
The failures I had on the boat were no doubt due to preparation defects - bits that I didn't take out, and do all the pre-treatments too.
Peter - here's what appears to be a local OZ version of the POR-15 (sorry for the slight Oz hijack JFH)
11-14-2007, 03:43 AM
I have years of experience with working with steel and stainless steel
You will hear many stories about what to do with steel.
Here is the simple awnswer. Bottom line.
Clean the steel by sand blasting or mechanical means to clean metal.
Treat with phosphoric acid which turns iron oxide to iron phospate.
Rinse with water. It also etches the surface.
Within 4 hours, paint with two part epoxy paint. 19 mils thickness. That is about the thickness of a dime.Two or more coats. And epoxy paint is 25% phosphoric acid by the way.
Thats it. END of STORY.
Look it up if you doubt me.
Alternatives. Hot dip Galvinizing OR Powder coating
Powder coating is slightly better than epoxy. It is a polyester coating baked on.
11-14-2007, 09:50 AM
There is a steel framed house on my block that has been standing for fifty years without a speck of rust. It was primed with this product.
I have used it myself over the past twenty five years for priming steel and cast iron with 100% positive results. It also stops topside weepers dead in their tracks.
11-14-2007, 02:01 PM
Mcmaster-carr sells the Devcon brand
mil spec is MIL-P-21035
about $15 pint/$30qt
I have been using it for years with excellent results
Great Advise! I think the sandblasting and acid trick is what I will use before any coating. Last time I used that method was on an old Triumph TR7. The paint job lasted till I sold the piece of junk.
The framing is not supposed to see any sea water but the boat has a center-board and I need to treat the inside of the case. The best way would be a bronze or wooden case but, to tear it all out would be another few months and we want to sail in the spring.
I'll try to get some pics up.
Again, thanks for the info.
11-16-2007, 08:56 AM
It will be great to see photos of your project JFH.
Bill Hirsch Miracle Paint. Similar to por15 but better. Originally formulated to paint rusting steal bridges. It is specially formulated to bond to rust and it does. It bonds to rust and stops the rust at the same time. It is amazing stuff.
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