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Should I remove powder coating from brass union nipples?

I had a few of my 2 pipe steam radiators powder coated. The shop said they would mask the brass union nipples that connect the radiators to the valve and traps. The radiators look great, but half of the union nipples have powder coat spray on the union nipples or in the nut's thread, or both.

The images below illustrate the range of the over spray:
  • In some cases a few specs or a dribble is on the brass union nipple
  • In some cases there is over spray on the union nut's threads
  • In some cases the entire union nipple has powder coat spray on it
Should I:
  • Ignore the over spray and fasten the radiators and hope for the best?
  • Gently scrape the brass unions clean and leave the nut threads as the are? If so, is there a preferred tool? Solvent?
  • Buy new unions? If so, what tool is best to remove and replace the unions? The unions are short and a pipe wrench is too wide to fit between the union's nut and the radiator.
  • Do something else?


  • mattmia2
    mattmia2 Member Posts: 9,670
    Probably not a problem. Little scotchbrite will take it right off.

    There is a special spud wrench to remove the spud from the radiator that firs inside to extract it. they are notoriously difficult to extract.
  • ChrisJ
    ChrisJ Member Posts: 15,706
    I consider that tool to only be for installing new spuds.  

    If those were mine I'd take the time to clean the mating surfaces but don't scratch them.

    To seal metal to metal the surfaces need to be near perfect.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • Jamie Hall
    Jamie Hall Member Posts: 23,324
    edited September 2020
    Those mating surfaces have to be perfectly clean, but they must also be perfectly smooth. Do not use anything which might scratch them. Scotchbrite probably will work, but I'm not quite as optimistic as @mattmia2 -- powder coat is likely to be really on there, and you have some work to do.

    Lucky you, though -- the threads don't matter. Not to worry about them.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,646
    edited September 2020
    That powder coat looks fantastic!

    I have radiation hoarding issues....
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • motoguy128
    motoguy128 Member Posts: 393
    I tried using a pad wrench to remove the spud on a 110 y/o radiator and a newer that was probably only 20 years old. They both laughed at me I think. A sawzall had 4 careful cuts in it and a cold chisel knocked it out. Probably took less than 10 minutes to remove. Easy. Spud wrench tightened the new one in.

    Actually had to change the bushing as well from 1-1/2” to 1-1/4”. Cut that out too. Similar way. 4 or 5 notches just short of the threads then use a 36” pipe wrench and they collapse Inward With the force and thread right out. Another win for tapered threads.

    Unless tape was used, probably not coming out. the brass is soft and the spud wrench will easily tear off the notches. Maybe some rot of impact might have worked.