Best flux core wire for watertight weld on contaminated metal?

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Hi!  I'm new here but have welded for many years.  I have an upcoming job that  consists of welding a new skin (16 gauge aluminized sheet metal formed in a U shape) on the bottom of two 110 foot long pontoons on an algae harvesting barge.  The sheet metal will be formed to fit (I hope) and will extend up the sides of the pontoons 8 or ten inches.  I will have to join the skin sections (butt weld) together every 12 feet or so.  I will have to grind the paint off of the welding areas on the pontoons (which will still be mounted on the barge as the whole thing is all welded together) but I am sure that I will still have some paint contamination and also the contamination from the aluminized coating even though I will be welding on the sheared edge of the sheet metal.  The job will be outdoors so I think I will have to plan on no cover gas, or at least figure problems for wind.  I'm looking for advice on what to use that will let me make water tight welds on this project.  I want to use wire (from my suitcase welder which does have gas capability) because it would be much faster than stick welding.  Any suggestions would be greatly appreciated!  I will probably have a lot of stops and starts because if I put too much heat in one place I'll have problems with warping.  If wind permits I'd use bare wire, but I'm thinking that I'll have cover gas problems.  Is there something out there that will do what I need to do?  Please advise.....linden77
Reply:Not sure on wire, but if it was me.  I would run a 6010.  I would rather it take longer and know it won't leak. than quicker and be worried about it.I'm a Lover, Fighter, Wild horse Rider, and a pretty good welding man......
Reply:The only quality wire I know of is NR211-MP.  I would have a hard time making it water tight with that.  440 feet Butt weld on 16 gauge?   Good luck. DavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:I have had good luck with NR211-MP on several roll off containers and trailers and holding oil (I know it's not the same as water) is a customer requirement. Some of these have been impossible to get all of the paint, rust and scale off of. Now on the other hand they don't sink either. Hammack's suggestion might be your best bet. I have used it for patching rusted through spots on a forty foot crew boat, and I honestly had no idea they used sheet metal that thin on boats. I don't guess it leaked as it had a one year warranty and that has expired with the customer never calling me back, but then again I don't know if he ever actually got it back in the water. I would feel safe using the 6010, not so sure about the flux core without actually seeing it. I will say that it's really easy to see when NR211-MP gets contaminants in it. Big bug holes.The difference between art and craft is the quality of the workmanship. I am an artist.
Reply:I would go with the 211 also. It has a fast fill and a pretty good flare so it should burn off any crap that you dont pre-clean. You can also kinda whip it like a 6010 or 11 rod...
Reply:Originally Posted by Hammack_WeldingNot sure on wire, but if it was me.  I would run a 6010.  I would rather it take longer and know it won't leak. than quicker and be worried about it.
Reply:Not wanting to speak for Jackson but I would say that, because its a fast freeze rod with a big flux flare, you could do an exaggerated whip and make your 'stack of dimes' and not blow holes and get a good weld.....
Reply:Hmmm, I was thinking 6013 in a small diameter for stick, or ER71T-GS fluxcore wire in .030.  I'm no expert on either of those process though.MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:Thanks for the suggestions.  I'll check in to that NR211-MP.  Is that a type designation or a particular brand?  I haven't used a whole lot of flux core wire so I need some education.  I did just rebuild a backhoe bucket  using Lincoln dual shield wire and it really worked well, although I found out after I was done that I was supposed to be running a higher gas flow.  I used about 20 cfm and the welding distributor said I should have been up around 30 cfm or so.  Is he right?  My welds looked good and the only problem I thought I had was when I ran out of cover gas.  I can tell you that the dual-shield wire (Lincoln ultra-core) did not like having no gas and let me know real quick when I ran out.  Thanks again for the advice and I can always use more.  Most of what I've learned in the 20 odd years I have been in business for myself is by asking lots of questions, especially from people who can do what I don't know how to do yet.  I can be taught!..........linden77
Reply:That is a Lincoln wire.....
Reply:TEK, hit it on the head.  Mainly because you can cut thru the crud, and it freezes fast enough to whip it and not burn thru. I have run 6010/6011 on sheet metal quite often with good results.  if it's clean metal a 6013 will do beautifully as well.I'm a Lover, Fighter, Wild horse Rider, and a pretty good welding man......
Reply:I prefer 6011 on DC over 6010 for really thin stuff because it has a softer arc and doesn't dig as deep as the 6010. It still has good cleaning action if you can't get all the gunk off your metal. 6013 does need cleaner conditions than the 10/11 stuff but makes a smoother weld.
Reply:I used to use the 6010 patching oil storage tanks and heater treaters and they were always nasty unless they had been sand blasted, and that usually just showed you that there were a lot more holes than you thought there were.The difference between art and craft is the quality of the workmanship. I am an artist.