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Stripping paint from Cast iron radiators using a lye bath

branimalbranimal Member Posts: 108
edited May 19 in Strictly Steam
I've got a few a 1-way steam radiators that sorely need a new paint job. I've read here and elsewhere that I can give them a lye bath prior to painting. I have some large plastic cement mixing bins. One for lye solution, one for a clean rinse.

I can plug the air vent (1/8 brass plugs) and main valve with black plugs. And drop them into the lye bath.

One issue is I have to do this indoor b/c two of the four radiators are absolute monsters. I can't get them down safely even with a handtruck.

Can I do this indoors on a job site? The floors are subfloors and I can leave them in a room that is well ventilated. And setup fans to exhaust the fumes.

Thanks!

Comments

  • PC7060PC7060 Member Posts: 9
    I don't have any experience with lye bath. I had my radiators sandblasted and powder coated, came out great. These were heavy monsters too, used movers to get them them in and out. The movers use lift straps and were very efficient.
    mattmia2
  • mattmia2mattmia2 Member Posts: 1,186
    Lye will remove the paint. If there is any rust it won't remove that. Powder coat will be a lot more durable than any paint you can apply in the field. I would be as concerned with spilling or dripping lye indoors as with the fumes. If you spill it, you need to clean it up so you don't get chemical burns or burn other things. It might be something better left to someone with the equipment and space.
    branimal
  • Jamie HallJamie Hall Member Posts: 12,703
    Allow me to be a bit more forceful than @mattmia2 . Lye is flat out dangerous to work with. You must -- no shortcuts -- wear heavy chemical resistant gloves, a water repellent if not waterproof bunny suit, and at least splash proof goggles (though I would recommend a full face respirator).

    Back in the bad old days the mafia used it to get rid of bodies they didn't want to ever turn up. For all I know, they still do. It works fast.

    Further, as @mattmia2 mentions, it won't take care of any rust.

    I have painted a number of radiators -- quite successfully. Wire brush to get rid of all the loose rust. Use a top quality primer (Benjamin Moore makes one) and then use a top quality acrylic paint (again, I use Benjamin Moore, but Sherwin-Williams makes a first class product, too). Don't skimp. Quality paint costs more -- and is well worth it. You don't want to do it over 10 years down the line.
    Br. Jamie, osb

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
    mattmia2branimalethicalpaulSTEVEusaPA
  • ethicalpaulethicalpaul Member Posts: 1,571
    Do you use a chemical rust converter for such tasks, @Jamie Hall ? Does it help to delay the rust from returning?
    1 pipe Utica 112 in Cedar Grove, NJ, coal > oil > NG
  • branimalbranimal Member Posts: 108

    Allow me to be a bit more forceful than @mattmia2 . Lye is flat out dangerous to work with. You must -- no shortcuts -- wear heavy chemical resistant gloves, a water repellent if not waterproof bunny suit, and at least splash proof goggles (though I would recommend a full face respirator).

    Back in the bad old days the mafia used it to get rid of bodies they didn't want to ever turn up. For all I know, they still do. It works fast.

    Further, as @mattmia2 mentions, it won't take care of any rust.

    I have painted a number of radiators -- quite successfully. Wire brush to get rid of all the loose rust. Use a top quality primer (Benjamin Moore makes one) and then use a top quality acrylic paint (again, I use Benjamin Moore, but Sherwin-Williams makes a first class product, too). Don't skimp. Quality paint costs more -- and is well worth it. You don't want to do it over 10 years down the line.

    I have everything you listed in terms of safety (chemical gloves, goggles, and a respirator with vapor filters). Unfortunately I don't have the tyvek/bunny suit. Going to see if my local HD got some back in stock. If not, there is a contractor safety equipment shop nearby.

    I'll pick up some rust remover.

    How soon after I strip one and clean it do I need to prime it? I take it you're not a fan of rustoleum primer. I have some on hand I was going to use with my HVLP spray gun. Will look around for a Ben Moore dealer near me.

    I've read guys aren't using high heat paint on radiators b/c of the off-gassing. With an acrylic paint should I use an oil based paint?

    Thanks!
  • Hap_HazzardHap_Hazzard Member Posts: 2,263
    I've used Rust Oleum high heat paint on a bunch of radiators and never had any "off-gassing" problems. I think the automotive paint for engine blocks smells bad when it gets hot, but the regular high heat paint is fine.
    Just another DIYer | King of Prussia, PA

    1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
    branimal
  • branimalbranimal Member Posts: 108
    Started the lye bath. took 6 gallons of water to get the water level to the halfway point on the radiator. I poured in 1lb of lye to start. Wondering if more lye is required.

    Going to check the water temp with a temp gun.

    Beer o'clock.

    Will keep you posted.
    EdTheHeaterMan
  • EdTheHeaterManEdTheHeaterMan Member Posts: 480
    If we don't hear from @branimal by Friday, someone should contact his Next-of-kin.
    branimalmattmia2
  • Jamie HallJamie Hall Member Posts: 12,703
    He's a braver man than I am...
    Br. Jamie, osb

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
    branimal
  • Big Ed_4Big Ed_4 Member Posts: 1,312
    :)
    I have enough experience to know , that I dont know it all
  • branimalbranimal Member Posts: 108
    edited May 21
    Things went great. I didn't add more lye b/c it was working within 30 minutes. Flipped the radiator after 5 hours and let it sit overnight. It looks like the rad is down to bare metal. It kind of looks like hot rolled steel. Greying and bluing. Part of me wants to clear coat it and call it done.

    There is some minor rusting in certain areas. I've got rust remover spray and wire wheels, rust remover discs for my grinder etc. Electrolysis is another option I'm considering to remove the rust.

    I'm going to transfer the clean rad to a washing bin and drop another rad into the used lye bath. Hopefully it still has some punch.

    My local HD only had 2 decent rustoleum colors. Flat black and hammered black. I like the gun-metal color. Will keep looking for it. Or maybe I'll clear coat it.

    What can I do to prevent new surface rust before I paint it?

    Here are some before & after pics.







  • mattmia2mattmia2 Member Posts: 1,186
    Spray it with a metal primer, the gray rustoleum should be fine for metal in that condition. Could also use automotive primer.
  • EdTheHeaterManEdTheHeaterMan Member Posts: 480
    if you don't want a color, you can spray with lubricating oil. This will retard the rusting process, but you will need to thoroughly clean the oil off the metal before you start to paint or clear coat. Store the oiled metal indoors out of the weather. A garage or basement is fine. moisture is a problem, temperature not so much.
  • dopey27177dopey27177 Member Posts: 276
    nice job. Dan has an article about painting radiatore and color combinations, read before you paint.

    Jake
    branimal
  • branimalbranimal Member Posts: 108

    nice job. Dan has an article about painting radiatore and color combinations, read before you paint.

    Jake

    Interesting article. I'm going either satin black or metallic black.

    With the cost of used radiators now, I wonder why people don't downsize their radiators if they're overheating vs building a radiator cover. I suppose it could cause issues b/c now the boiler is becoming too large for the radiator's it is supplying.

    Here's the painting link for others to check it out:

    https://www.supplyht.com/articles/101777-dan-holohan-metal-paints-and-radiators


  • Joe_DunhamJoe_Dunham Member Posts: 28
    If you want to shrink the radiators, You'd be surprised how easy you can separate the sections with hardwood a wedge top and bottom. Thats if you want to make the radiator smaller. You just have to hope the push nipples wind up where you want them. If you heat the section top and bottom where you want the nipples to come out of you have a better chance. Then use a light smear of red RTV to re-assemble.
  • ethicalpaulethicalpaul Member Posts: 1,571
    The easiest way to shrink a radiator is to put a blanket on it.

    But to address @branimal 's query about people getting smaller radiators, I have done it. My massive living room one failed and I replaced it with a smaller one from Craigslist. But it's a hassle and a backbreaker that very few homeowners are willing to take on. And it doesn't seem to be something that many of them think is worth putting money into.
    1 pipe Utica 112 in Cedar Grove, NJ, coal > oil > NG
  • mattmia2mattmia2 Member Posts: 1,186
    You can always add a thermostatic valve to the vent to keep it from heating if the room is too hot, possibly more expensive but certainly much easier and less risky than trying to resize the radiator.
  • SteamCoffeeSteamCoffee Member Posts: 78
    Lye is great stuff, use it properly! It’s a wonderful paint stripper, use Phosphoric Acid on rust (Ospho is a good product). You’ll need about a 1lb per 5 gallons min. Heat will make it work much faster, about 4 times, as will agitation. After you remove it, it needs a ton of rinsing. The it will start rusting, use cold water for this, seems to give me more time. Afterwords, I use Acetone Rinse as it cleans everything thing up nice and absorbs water. Flash rusting can be quickly treated with Phosphoric, let it dry overnight. I prefer oil based primers and top coats, Benjamin Moore makes great primers and Impervo topcoat is top shelf stuff. I have safely used Lye for cast iron engine blocks, gear boxes, Pans and a host of other things. It’s a do all chemical. PLEASE exercise caution and follow basic safety procedures, your eyes will be the most vulnerable, I use swimming goggles as I’d lose my job AND my eyesight if I screw it up! I use white vinager to neutralize. Ps, don’t use on aluminum etc. take some pics of the finished product.
    branimal
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