Brazing Aluminum

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I have been asked if i could do a job which involves repairing cracks in some aluminum pontoons for a boat,I have never brazed aluminum before and am wondering if it is difficult,how do iknow when it is hot enough to add filler?I can't use my mig because of the remote location(a cottage 30 miles from electricity)and i don't have a generator.Any help or advise appreciated.Lincoln 225 ACLincoln Mig Pak 15Lincoln Mig Pak 10Purox Oxy-Acet Outfit20 Ton PressHonda Generator
Reply:I wouldn't recommend brazing.  Tig weld repair is what I recommend.
Reply:The short answer is you know the aluminum is too hot when it suddenly transforms from a dull metallic solid to a shiny metallic liquid.  The solid-liquid transition for aluminum happens over a very small temperature range.  As a result, it can be very challenging to braze aluminum.You've got no margin for error in this particular job either.  The repairs have to be water tight, as I'm sure you already know.If you're intent on trying to repair this pontoon, I strongly suggest you practice on some aluminum that is similar in thickness to what you're going to repair.  Get very confident on some practice pieces, and work with them in the position that you'll have to work in on the pontoon.  I further suggest that you make them similar in size, because aluminum conducts heat very rapidly, and small pieces will overheat and melt much faster than larger sections.Because aluminum melts at a much lower temperature than steel, I also suggest you find a heat source other than oxy-acetylene or oxy-MAPP or oxy-Propane.  You might start with an air-propane torch, like plumbers use to sweat copper joints.  The heat output of this flame is much lower than any oxy fuel source.  The lower heat output will let you slowly and gradually approach the critical temperature in the braze joint.If the propane torch is too low in heat output, I've heard that oxy-hydrogen flame can be used.  But this has it's own hazards.  Hydrogen will likely cost you to rent a cylinder, and it's much more hazardous to work around because the flammability limits for hydrogen are much broader than other fuels.  The hydrogen flame is almost impossible to see as well; further complicating matters.  In fact, the more I think about it, the more I hope you can do this with a propane torch....If not try oxy-propane and hope for the best.Benson's Mobile Welding - Dayton, OH metro area - AWS Certified Welding Inspector
Reply:PAweldor, he doens't have access to electricity at the jobsite, and I gather the boat can't be moved to his shop.  That's why he's asking about brazing. Originally Posted by paweldorI wouldn't recommend brazing.  Tig weld repair is what I recommend.
Reply:Alumaloy rods? I've used them. Worked quite well. Not as great as a full tig job but worked never-the-less.
Reply:I just bought some of those durafix aluminium brazing rods , you use a propane torch and they are great for thin aluminium, Durafix.com. the secret is to clean the crap out of the aluminium and they stick great, they have a surface tension that lets you seal right over 1/4 holes and bigger. you can google it and see a video if the rod being used.yeah its not tig but it has its place, just like your situation..
Reply:Sounds like job I'd pass on.  It could turn into one of those"Why did I ever.." jobs...I just tell folks "I'm not set up to weld aluminum".  It's generally bad practice to "learn" on a paying job for someone...and not all beginner's attempts turn out well...as a matter of fact, few do!"Good Enough Never Is"MIller AC/DC  ThunderboltHobart HH180, 125EZRiland Cut 40 Plasma oxy/act  outfitTons of "stuff", all treasures to me!
Reply:The guy with the boat tells me he believes that the pontoons are 3/16 thick aluminum.I think i'll grab a few pieces from my local scrapyard and practice a bit and see how it goes.If i'm not completely confident i can do good repair i won't try it.Lincoln 225 ACLincoln Mig Pak 15Lincoln Mig Pak 10Purox Oxy-Acet Outfit20 Ton PressHonda Generator
Reply:Originally Posted by A_DAB_will_doPAweldor, he doens't have access to electricity at the jobsite, and I gather the boat can't be moved to his shop.  That's why he's asking about brazing.
Reply:The customer is in no big hurry,we still have to wait 2-3 weeks for snow to melt to get to his cottage where the boat is.I am thinking about selling my little honda 2500watt and getting a used 5000 +watt than my mig would be portable.Lincoln 225 ACLincoln Mig Pak 15Lincoln Mig Pak 10Purox Oxy-Acet Outfit20 Ton PressHonda Generator
Reply:Added costs for the repair with Mig is Tank of Argon, AL liner kit for the Mig pak 15 and feeding AL is a PIA.If this is something that you could get a couple more jobs outta I would sell both Lincolns and get a new 180 and a Spool Gun.Ed Conleyhttp://www.screamingbroccoli.com/MM252MM211 (Sold)Passport Plus & Spool gunLincoln SP135 Plus- (Gone to a good home)Klutch 120v Plasma cutterSO 2020 benderBeer in the fridge
Reply:If your dragging the torches up there, why not just weld it?
Reply:That's what this is about i have never brazed aluminum and was wondering how difficult it was.Lincoln 225 ACLincoln Mig Pak 15Lincoln Mig Pak 10Purox Oxy-Acet Outfit20 Ton PressHonda Generator
Reply:Forget the alumarod/brazing aluminum.  All you'll do with that junk is make the repair more difficult/impossible to repair correctly.Mig, without a spoolgun, is not the solution either.  Even with a spoolgun, that material is pretty thin, and without considerable experience with aluminum/mig, you'll probably blow right through.  What caused the cracking to begin with.  Was it due to striking something or was it a failure of the base metal due to fatigue.  If it was due to fatigue/corrosion, you've got bigger problems to deal with.Has the owner ever hear of a TRAILER?  He had to get the boat to it's current location somehow.Tig is the only process I would consider for this repair.  Either in the shop, where you can control the environment, or with a portable tig (read Dynasty 200) which could be run off a generator.There are a lot more questions that need to be asked and answered before taking on this project.  When dealing with aluminum which has been used in a hostile environment (in the water), you're dealing with a different animal than the coupons you get to practice on.Without some experience in the field, and without the proper equipment, this is one I'd probably pass on.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:Originally Posted by bensweldThat's what this is about i have never brazed aluminum and was wondering how difficult it was.
Reply:I 'm beginning to agree sundown ,this job is probably better off left to someone with portable tig.He says he converted the trailer into a camper,guess the boats there for good.Lincoln 225 ACLincoln Mig Pak 15Lincoln Mig Pak 10Purox Oxy-Acet Outfit20 Ton PressHonda Generator
Reply:Originally Posted by bensweldI 'm beginning to agree sundown ,this job is probably better off left to someone with portable tig.He says he converted the trailer into a camper,guess the boats there for good.