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  1. #1
    Join Date
    Aug 2017
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    28

    Exclamation Things you shouldn't weld!

    Being new to welding I have been reading a few welding forums and learned there are some things you shouldn't weld on and some you can with special precautions. Most of you probably know all this but it might help a beginner. A few things here are common sense but some I was not aware of and no one needs to learn some of this the hard way.

    If you have something to add or can correct me on any of this please share your knowledge!

    THINGS YOU SHOULD NOT WELD ON.

    1. If it is holding pressure, don't weld on it.
    2. If something flammable was at any point inside it, don't weld on it.
    3. If it's under extreme load, don't weld on it.
    4. Don't weld on anything galvanized before first removing the layer of zinc. It is TOXIC.
    5. Don't use brake cleaner to clean metal. Brake cleaner gets very TOXIC when heated.
    6. Don't weld on a gas tank.
    7. Don't let the electricity pass through bearing, shafts or movable parts. Stray shorts looking for ground can lock up
    a machine and ruin it quick.
    8. Don't weld on any tank or like structure until you know what's inside or has been inside it.
    9. Don't weld cast aluminum pistons. They can have gas pockets inside and explode.
    10. Don't weld something sitting directly on concrete.
    11. Don't weld over industrial paint coatings or powder coating.
    12. Avoid welding directly on wood if you can avoid it.
    13. If you are not sure, don't weld on it.

  2. #2
    Join Date
    Sep 2003
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    Clark County, NV
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    Quote Originally Posted by Nipper View Post
    4. Don't weld on anything galvanized before first removing the layer of zinc. It is TOXIC.
    Depends on how much you are doing and where you are doing it, and how good you are at holding your breath.
    9. Don't weld cast aluminum pistons. They can have gas pockets inside and explode.
    Never heard of that one. Though I can't fathom the need to weld on a piston and expect the piston to still be useful anyway.
    10. Don't weld something sitting directly on concrete.
    11. Don't weld over industrial paint coatings or powder coating.
    12. Avoid welding directly on wood if you can avoid it.
    I've welded LOTS of things sitting on concrete. What's the concern here? The perfect finish of the concrete?
    Welding over coatings depends on the criticality of the weld. If not critical, I've done it many times, with the biggest concern being establishing the arc, and best when done with a flux-bearing process like Stick or FCAW.
    Like with concrete, I've welded on top of wood many times. The big thing is that it's a small weld and you are expecting the wood to get charred a bit.

  3. #3
    Join Date
    Aug 2017
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    28
    Quote Originally Posted by MAC702 View Post
    Depends on how much you are doing and where you are doing it, and how good you are at holding your breath.

    Never heard of that one. Though I can't fathom the need to weld on a piston and expect the piston to still be useful anyway.

    I've welded LOTS of things sitting on concrete. What's the concern here? The perfect finish of the concrete?
    Welding over coatings depends on the criticality of the weld. If not critical, I've done it many times, with the biggest concern being establishing the arc, and best when done with a flux-bearing process like Stick or FCAW.
    Like with concrete, I've welded on top of wood many times. The big thing is that it's a small weld and you are expecting the wood to get charred a bit.
    I'm with you on the piston and none of this may be gospel, they are just things I have seen posted in a few places.
    IIRC welding on concrete could make it crack. I really dont know and I weld on concrete all the time since I dont have a table.

    On the wood it said it could get hot and make gases that would effect the weld.

    Is the zinc thing really that bad? A few people said it could kill you. Also the gold colored coating (not sure what it is called) that you see on unistrut.

    Again, I saw these items more than once so I thought they might have merit but, you know... This is the internet.

  4. #4
    Join Date
    Nov 2010
    Location
    Maryland
    Posts
    887
    For galvanized metal I hit it with a flap wheel if I'm using 7018; the zinc burns and the resulting deposit has porosity. For 6010/6011 it's much more tolerant, but for critical stuff I still clean it off. Definitely don't breathe the fumes....it can really make you feel like s**t. Did it exactly ONE time. Never again.

    The gold coating is probably Iridite which contains chromium. The heat of welding turns it into hexavalent chromium which is carcinogenic. More on that here: https://www.osha.gov/OshDoc/data_Gen...t_chromium.pdf

    Now about welding on wood......got a rod that is "all purpose"? It "wood" be nice to be able to weld pine to oak, poplar to fir....
    CanoeCruiser
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    Angle grinders, vicegrips, the usual suspects
    Two hands, tired body, not enough time...

  5. #5
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    Sep 2003
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    Clark County, NV
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    Quote Originally Posted by canoecruiser View Post
    ...It "wood" be nice to be able to weld pine to oak, poplar to fir....
    Not likely needed with all the beeches around here.

  6. #6
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    Sep 2003
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    Clark County, NV
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    Quote Originally Posted by Nipper View Post
    ...Is the zinc thing really that bad? A few people said it could kill you. Also the gold colored coating (not sure what it is called) that you see on unistrut. ...
    Zinc oxide is surely a thing, but it's relatively easy to abate. A cheap N95 nuisance mask will do most of it, even better if it's been correctly fitted to your face. I'm not talking about the super cheap sweeping masks, though. The Zinc oxide fumes are relatively large.

    Cadmium plating may be a different story, and you can Google the "experts" on that one.

    Again, welding outdoors and/or with good ventilation while not sucking in the fumes as they come off makes a big difference. I've welded more galvanized steel than I should probably admit to, and everyone around here will tell you I'm just _________.
    Last edited by MAC702; 11-15-2017 at 11:19 AM.

  7. #7
    Join Date
    Jan 2017
    Posts
    25
    what's wrong with welding on concrete? i do it all the time. cutting with a torch is a bad idea as the molten metal will melt into the concrete

  8. #8
    Join Date
    Feb 2009
    Location
    california
    Posts
    485

    Just protect from zinc smoke.

    I weld galvanized steel all day. 99% of the steel at work is galvanized, with most of it being hot-dipped. Just protect yourself from the fumes and (of course) the extra spatter. Flat, tube, angle, everything is coated. I wear the 3M half face mask with pink filters. Other guys have started using the Miller mask as it is what the welding store is pushing now.
    steel fence and gate shop worker
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  9. #9
    Join Date
    Mar 2003
    Location
    Calgary
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    1,914
    Quote Originally Posted by Andy578 View Post
    what's wrong with welding on concrete? i do it all the time. cutting with a torch is a bad idea as the molten metal will melt into the concrete
    This is mis-stated, and should be "You should never transmit welding or cutting heats to concrete". The reason is that concrete contains pockets of moisture, and when heated directly by welding or cutting, these may turn to steam and cause an explosion, with flying particles of concrete,

  10. #10
    Join Date
    Aug 2017
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    28
    Quote Originally Posted by Northweldor View Post
    This is mis-stated, and should be "You should never transmit welding or cutting heats to concrete". The reason is that concrete contains pockets of moisture, and when heated directly by welding or cutting, these may turn to steam and cause an explosion, with flying particles of concrete,
    I had a chance to look this up again and the above statement is similar to what the original author stated. I don't know if its a valid concern or not but thank you Northweldor.

  11. #11
    Northwelder is correct. If concrete gets hot enough the moisture pockets trapped in the concrete can cause the concrete to "explode".

    Keith

  12. #12
    Join Date
    Nov 2017
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    13
    i thought if brake clean was non-chlorinated it was ok?

  13. #13
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    Jul 2012
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    Quote Originally Posted by nonstopgo68 View Post
    i thought if brake clean was non-chlorinated it was ok?
    That was my understanding too.... Waiting for denial or confirmation also...

    Dale
    Lives his life vicariously through his own self.

  14. #14
    Join Date
    Nov 2010
    Location
    Maryland
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    I use acetone to de-grease whatever is to be welded and if necessary, then a wire brush, wire wheel or flap disk for rust or mill scale. I de-grease first to prevent grease getting onto the brush or wheel (and getting spewed all over the place). I use acetone to clean aluminum and use it for steel because it's already here. Can't tell you if non-chlorinated brake cleaner is safe or not but the chlorinated stuff can be deadly.

    No matter what you're welding, always keep your head out of the smoke plume.
    CanoeCruiser
    Harris dual-stage O/A
    Lincoln AC/DC buzzbox
    Hobart IronMan 210
    Lincoln PowerMig 135
    Miller 3035 spoolgun
    Thermal Arc 185
    Thermadyne Cutmaster 52
    Angle grinders, vicegrips, the usual suspects
    Two hands, tired body, not enough time...

  15. #15
    Join Date
    Aug 2017
    Posts
    28
    Thank you all again! Please add all you can.
    Maybe someone will find this post from a search and it will help them like it has me.

    Some very important information here for beginners!

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