Will this be a good idea?

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Told a neighbour I needed to replace old RV bumper on fifth wheel, told him I needed 4" square tubing, he deals in picking up scrap cars and metal as a money making hobby in his retirement, well I wasn't home when he came by, but here is what he dropped off, it is twelve feet long with a 4 1/2" diameter.Seems to be galvanised, my problem is, is it safe to cut to seven feet and then try to weld it in place with my arc welder, I have heard it is not good for ones health to cut or weld this coated metal.Plus it is hard to weld a mechanic told me.I cut a very heavy thing off that had been on the back to carry a motorcycle, so this would not weigh as much, all though it looks to be about 1/4" thick pipe.I would also have to come up with a spare tire carrier as mine is made for the old 4" square tubing, so wonder if it would be better just to get some 4" square tubing uncoated and start fresh.Any input?
Reply:The white smoke that comes up from very hot galvanized items is zinc oxide.  It is toxic and is very bad for you to breathe.You can cut and weld it safely if you wear a respirator with cartridges rated to stop this smoke or wear a "supplied air respirator" (with an air pump and long tube that allows you to breathe air taken in from a location remote from and upwind of your welding/cutting operation.  Don't use a hardware store respirator with generic dust filters or solvent vapor cartridges.  Consult your local safety equipment dealer for a mask and cartridges specifically rated by the manufacturer for zinc oxide smoke.Cartridge filter type respirators rely on a good seal around the face to provide safe air because you create negative air pressure inside the mask by drawing air through the filters.  Negative pressure combined with a poor seal around the face allows toxics to be drawn into the mask.  Don't use that type if you have a beard or for some other reason you can't get a good seal.  Test by covering the air intakes and trying to breathe.  You should not be able to draw ANY air into the mask with the cartridge intakes sealed.The supplied air respirator (the type with a large, low pressure air line - not the type with a small, high pressure air line) is more expensive than a cartridge respirator, but is inherently safer around toxic airborne materials because it always has slight positive pressure inside the mask.In addition to the respirator I would also use a small fan near the work to DRAW the smoke away from the work and exhaust it downwind from the work.  Drawing the smoke away from the work and exhausting it downwind from you is more effective and less disruptive to the process than blowing the same amount of air onto the work.awright
Reply:You can cut and weld the galvanized. Just don't breath the dust when cutting, or breath the fumes when welding! Don't breath any fumes from welding any material, or cutting for that matter. The rest of the project you are asking about is totally up to your discretion.Miller Thunderbolt 225Millermatic 130 XPLincoln HD 100 Forney C-5bt Arc welderPlasma Cutter Gianteach Cut40ACent Machinery Bandsaw Cent Machinery 16Speed Drill PressChicago Electric 130amp tig/90 ArcHobart 190 Mig spoolgun ready
Reply:Sand or grind the galvanize off of it grinding back a couple of inches around the cut or weld area and then weld it up. Do it outdoors and stay upwind and you should have no problems. That's how we did it in the oilfield and when I was welding for ironworkers.The difference between art and craft is the quality of the workmanship. I am an artist.
Reply:Thanks for the replies, and yes I do have a beard, had not even thought of that aspect of it, I would not be able to wear a regular face mask, would have to borrow an air supplied if I could.
Reply:If you are working outside just stay upwind from the weld and let the wind carry the smoke away from you. If working inside or no wind outside use a fan to blow the smoke away from you. It isn't that big a job so you won't have much exposure. It isn't really hard to weld without grinding off the galvanizing with the proper rod and technique. If you grind off the galvanize it's just another piece of mild steel.If I were putting it on my RV I would opt to purchase a piece of 4" thin wall tube just to keep from adding so much weight to the RV but that is just my opinion.
Reply:I would just grind it off.   Remove the galv and its no longer a problem.  It will be on the inside too, so be aware, or grind the inside too.  I got too much of that white smoke once.  You don't want that to happen, believe me.  DavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:If you're dive certified, just hook up your tank and reg and breath off the tank...Build a Barstool Racer at BarFlyRacers.com!
Reply:I realize this is probably overkill for what you want to accomplish, but if you have any interest in building your own supplied air respirator for current or future projects (like painting in interior spaces, as I did with very strong smelling epoxy), see my post at:http://weldingweb.com/vbb/showthread.php?t=21309I'd be glad to elaborate on how I built mine, if you are interested.While I recognize my excessive caution, I disagree with the concept of just standing upwind of the work to avoid the fumes.  Whenever I try that with stick welding, eddy currents around my body always draw fumes into my breathing zone.awright
Reply:Thanks again for all replies, have not talked to the neighbor that dropped it off yet, but for the one comment from Oldtimer on weight, I kinda wondered on that too.But like I say, when I bought the fifth wheel it had a mount welded to extend the bumper to fit a motorcycle, and it hung out almost three feet and was all C-channel and must have been at least three sixteenth of an inch thick or thicker and it made the unit way too tail heavy, so just cutting that off, lightened it alot, so I figured I was not adding that much this time.But square channel was my first preference like the original one that came with these.