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Welding an Aluminum Boat?

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A friend has a 30 foot boat with an aluminum hull that need work.  Lot of holes in the hull for various devices he no longer wants there.  He asked me if I could weld/patch these holes with my tig welder.  My tig welder is basically set up for working in the shop and near my welding table.  But, I do have an old Lincoln AC 220 stick welder that would reach the inside of the boat with my extension cable/cord built for 220 operations.  I heard that they make a rod that will weld aluminum.  Is this correct and can I do this with my AC welder?  What number is this rod, who makes it, and is it really expensive?  

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Most alum stick rods I'm familiar with run on DC not AC. Alum stick  best is for thick materials because it needs to be run hot. I played with some 3/32" alum rods at the tech school last semester with 2 of the other instructors on some 1/8" 6061 and it was very difficult not to blow holes in the 1/8" material. The puddle was super fluid and out of position welds were almost impossible for most guys. One other issue with alum stick rods is they burn super fast, Expect them to run almost 3 to 4 times faster than typical rods like 7018. This makes holding an consistent arc length super hard and as soon as you start to long arc the rods the weld gets out of control. The short rods were almost done before you blinked. I'm not sure if they make a stick for typical 5xxx series marine alum. All the ones I've seen are for 6XXX alum. Corrosion would be a big issue if you have a saltwater environment. Last issue is the flux coating is highly corrosive, so you'd need to be sure you got all the flux cleaned off well.


I can dig around and see if I can find what's left of the box of rods. I forget who made them, but they weren't horribly expensive for the small 1 lb box. Best bet would be to go talk to your LWS and see what they have on hand. You can try some, but I seriously doubt you'll be happy with the results.



Mig would be a better choice. You have a wider variety of "flavors" available to match alloys and you can often get them in the small 2 lb spools easily. To do alum you need a 230v capable machine with a spoolgun. A 180 amp class mig maxed out with voltage and wire speed will do 1/8" alum. A 200 amp or larger mig would work better because it gives you more room to adjust settings for control. Don't even bother with a standard mig gun. Without a spoolgun the wire will birdsnest unless it's dead straight even with the suggested teflon liners they sell supposedly so you can do alum. . Because it's also a hot process, alum thinner than 1/16" is almost impossible unless you have a fancy dedicated alum mig that does pulse mig. Then you can go down to maybe 20 ga at best with the right settings. Again it's a hot fast process. Expect to go 3 times as fast as you would with typical gas / solid wire mig. To do alum mig you use 100% argon, not typical mig mixes.



Tig is the best option. unfortunately even if you picked up a HF unit for yours, without a pedal, it's an effort in frustration at best. To do this you really need a small AC/DC tig like a Dynasty 200. You may be able to rent one depending on your location.

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MY first choice is drilling out for a "solid rivet", although you need access to both sides to set the rivet.

Tig welding is my opinion also - 3/32"-5356 filler or a more common rod is 4043 - for a small screw hole or such either will work fine from my 30+ years doing this.
If your not set up and or comfortable welding thin mat'ls, your better off referring him to a welder that does it more often. Not that you couldn't possibly do it but things can go bad quick with blowing the hole bigger and the metal warping.
Also be aware there may be foam inside (both the transom area and under the floor if it has a floor) which will pose it's own nasty issues while welding.

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welding alum boats is NOT a walk in the job !  arc rod not going to work unless you're WAY better than most GOOD welders !

you need tig & wire feed set ups depending on what your welding on the boat also on tig sometime you cant use foot pedal

cause your up inside it LOL so your choice is have someone else run the foot petal for you WITCH is really FUN !!!

or have a tig torch that has a adjustable power switch on it & you use your fingers to control it learn curve there to !

also its an inside the shop job, out of the wind cause of the argon gas needed !!


right rod for that kind of job is 5356


I do this kind of work often and its not easy & I have everything I just said and then some !

I would take it to a boat welder if its just small holes to fill should be easy with RIGHT Eqt


Steve,s Welding & Fab

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I have welded up two aluminum boats. one minor and the other quite alot of welding. On both of them I used and oxy/acet set up and flux core rod.
i also welded a lot of aluminum in that time period with the same set up and on a bit i welded two aluminum soda cans together on the tops. I wouild have never been able to do any of it with stick rods and my lincoln tombstone.  I never took the time to learn how to use that set up.
For each of the boat repairs i put the hulls in position to not have to do much in the way of position welding. One of them was about 20 long so that took a bit with good help.
Best advice I can offer is walk away from this and pass it on to someoone set up and skilled.

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I have welded small drill holes in an  aluminum boat hull ,with aluminum foil rolled tightly as filler rod, with an Ox-Acet. cutting torch . Not a method to be recommended . My suggestion is find a welder/fabricator nearby who has a MIG and the spool gun for Al.

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