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Thread: Welding over cutting oil

  1. #1
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    Welding over cutting oil

    Hey all, not sure if Iím being paranoid but I figured Iíd be safe rather than sorry. Iím a hobbyist welder/machine tool operator (wouldnít dare call myself a machinist at this point) and I use rapid tap a lot while machining parts. Now Iíve already welded parts Iíve machined but Iíve cleaned them very well as I always do. I just so happened to look at the bottle of rapid tap the other day and it says there are chlorinated parafins as an ingredient. Now Iím no chemist but just got me thinking is it similar danger to be welding on metal ive used cutting fluid on as a metal that has been cleaned with chlorinated brake fluid? Again, no chemist, just trying to be safe/cautious. Thanks!

  2. #2
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    Re: Welding over cutting oil

    Since degreasing with a chlorinated solvent, gases like phosgene, hydrogen chloride and chlorine gas can be produced, I would clean that off first.

    Now that tapping fluid is likely not Tetrachloroethylene so I'd bet that phosgene gas is not produced. But chloride gas can kill you in a large enough dose.

    One of my friends actually was in a chloride accident and died from it. He was revived and says he definitely went to the afterlife.

    I'm no chemist either So just my $0.02
    Dave J.

    Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~

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  3. #3
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    Re: Welding over cutting oil

    Quote Originally Posted by MinnesotaDave View Post
    Since degreasing with a chlorinated solvent, gases like phosgene, hydrogen chloride and chlorine gas can be produced, I would clean that off first.

    Now that tapping fluid is likely not Tetrachloroethylene so I'd bet that phosgene gas is not produced. But chloride gas can kill you in a large enough dose.

    One of my friends actually was in a chloride accident and died from it. He was revived and says he definitely went to the afterlife.

    I'm no chemist either So just my $0.02
    When you just heat the part that has that chemical on it the fumes by volume are small. However, if you did it every day it could be very bad. A place out by me was using 111, Trichloroethane to degrease parts for greenhouse enclosures before sealing them. They used electric heaters for that reason but even the electric heat was enough to create some phosgene and with years of exposure it was found that many workers had gotten lung disease from it.

    If you have a kerosene, propane, or diesel fuel space heater and you allow the fumes of certain perchloroethylene carburetor cleaners to run through the space heater it is pretty bad, just like when someone in the gas station after being warned about the car running when using the cleaner in the engine compartment will create visible phosgene gas from the exhaust pipe. But if you run 111-trichloroethylene through a space heater it instantly fills the room with immediately deadly phosgene gas.

    Sincerely,

    William McCormick
    If I wasn't so.....crazy, I wouldn't try to act normal, and you would be afraid.

  4. #4
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    Re: Welding over cutting oil

    I have welded where cutter oil was part when 18.
    If work for a company it there decision weld up wind.

    I would not recommend welding over oil as the weld may as good.
    I used steam cleaner, today I use a high pressure washer under $100.00.
    I use brush for cutting oil.
    Most of my machine work is dry save a few steps.

    Dave

    Quote Originally Posted by Threadkiller View Post
    Hey all, not sure if Iím being paranoid but I figured Iíd be safe rather than sorry. Iím a hobbyist welder/machine tool operator (wouldnít dare call myself a machinist at this point) and I use rapid tap a lot while machining parts. Now Iíve already welded parts Iíve machined but Iíve cleaned them very well as I always do. I just so happened to look at the bottle of rapid tap the other day and it says there are chlorinated parafins as an ingredient. Now Iím no chemist but just got me thinking is it similar danger to be welding on metal ive used cutting fluid on as a metal that has been cleaned with chlorinated brake fluid? Again, no chemist, just trying to be safe/cautious. Thanks!

  5. #5
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    Re: Welding over cutting oil

    So take this with a grain of salt, because nowhere here am I saying "It's safe". But breaking down the chemistry: Chlorinated solvents (tetrachloroethylene, trichloroethylene, chloroform, etc.) can be oxidized in the presence of ultraviolet light to form phosgene gas. These molecules are structurally different than the chlorinated paraffins present in rapid tap. Oxidation of chlorinated paraffins typically produces long-chain alkanes as a product of the reaction, but may not be limited to that. There is very little literature on the decomposition products of chlorinated paraffins in the presence of a welding arc, but they are anticipated to be potential human carcinogens and some do have the potential to form irritant and poisonous gasses when exposed to flame. Do these gasses contain phosgene? Maybe, not necessarily. It depends on exactly what's in rapid tap, which is a proprietary mixture. Probably not as bad as welding directly over a chlorinated solvent, but there's not very much safety data there.

    So that leads in to the next part- welding as a whole is known to produce hazardous, carcinogenic, and irritant fumes. Are the fumes from a little bit of rapid tap residue worse than the various metal oxides and other hazards that make up welding fumes? Maybe, maybe not. If you're concerned about your lung safety when welding, it's already a good idea to minimize exposure to gasses and fumes created during the welding process. Stay out of the plume of smoke, weld in well-ventilated areas, and use respiratory protection applicable to the potential hazards when welding in enclosed spaces. The best, safest option would be to substitute a non-chlorinated tapping fluid, such as some of the biodegradable options offered by Tap Magic/CRC for parts you plan on welding. If you want to continue using rapid tap and still err on the side of caution, you could always clean your machined parts prior to welding with a non-chlorinated solvent such as acetone. Combine that with proper ventilation and welding fume control, and you will dramatically lower your risk of exposure to hazardous gasses.

    Personally, I try to keep my parts clean but don't worry too much about it because I'm already treating welding fumes as an inhalation hazard. I definitely don't use tetrachloroethylene or other chlorinated solvents in the shop any time I plan on welding, but I don't sweat the cutting oils too much since I'm already removing the bulk of them from the part to not negatively impact the welds. I always wear a respirator when welding indoors, and try to get as much ventilation going as possible without blowing away my shielding gas.

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