welding the deck frame

Howdy all,

I'm building a deck in my small tin boat and I decided I'm going to go with aluminum and weld it. A friend loaned me a Millermatic 130XP wirefeed welder and I'm looking for how to set it up to weld aluminum.

does anyone have any experience with doing something like this? will this welder even work?

Your better of with a spool gun but it can be done. Make sure you have the right gas for Al and try some test welds first on some scrap.

Much lees heat is needed for Al, its real easy to burn through. Watch some youtube videos first.

thank you!

Rule of thumb is 1 amp for every .001" of material thickness. Use 100% argon at 20 CFH (more flow if you're outdoors), and use ER5356 aluminum wire, as 4043 will corrode.

Immediately before welding, thoroughly clean your weld area with a stainless steel wire brush. Do not use carbon steel, it will contaminate the weld.

As mentioned, a welder with a spool gun is the best tool for welding aluminum.

PSG, pretty summed it up, yes go with 5356, 4043 welds like crap. He makes a important point on not using a contaminated wheel, even if the wheel is stainless, do not use it on anything else other than aluminum as it will contaminate the wheel. Very important point PSG, Thanx for bringing that up. The only thing I can add is when attempting to use a spool gun, depending on the thickness of the material, such as 1/4 material, preheat the thicker material so it will flow with the lesser material and make a decent weld. if you are welding 1/4 to 1/4 such a piece of angle or flat bar, put the heat to it, i usually guesstimate, but i think 350 is an average rule of thumb, you can buy a temp stick from a local weld supply, but who really needs it, just heat it up n go with it. you will get the feel. provided the gun your are using is up to the task. Aluminum takes a lot of heat to make a good penetrating weld, home depot, harbour freight, lowes, etc... welders are not up up t0 the task. Don't waste your money on these and think you can weld aluminum. As far as the 130 xp goes, it will never get hot enough to make a solid weld, Thank your friend and take it to a welder, trust me you will be way better off.

It's not that 4043 wire welds like crap....... in fact, 4043 welds are quite clean, while 5356 welds are sooty. This wire also produces a LOT of smoke. However, the soot and smoke is a result of the additional alloys added to 5356 to make it corrosion resistant.

Also, 4043 is a much softer wire (because it's pure aluminum, not alloyed) and as a result, it is more prone to jamming, especially in a conventional MIG welder. While you may be able to pull it off with 5356, you can forget about trying to run 4043 through 15 ft of a MIG gun lead, you'll spend more time digging bird nests out of drive rolls and cussing, than you will spend welding. For this wire, you absolutely have to have a spool gun.

When I first started welding, I worked for a while at an awning company. We welded a lot of aluminum frames. We used 4043 wire for all our work. A while later, when I started working on boats, another welder told me to never use 4000 series wire in a marine application. I unknowingly did it one time, to repair a corrosion hole in a customer's boat. A couple of years later, low and behold, same spot was leaking again, and the corrosion was worse. Lesson learned. Fixed it with 5356 and that was the end of that problem.

Preheat thick aluminum parts. Anything 1/4" or thicker needs to be preheated, or the bead will just lay on top of the material, and it will peel the first time you put a load on it.

And finally, always remember that aluminum is 1/3 the strength of steel. This means that when you are laying out your design, it will call for additional bracing, or at least additional weld points. Even so, there are some instances where welding isn't going to be strong enough. Take for instance most aluminum boat trailers. Note that cross members are usually U-bolted, not welded. This is because it's joining thick sections of aluminum together, and as mentioned, thick aluminum doesn't take a bead as well as steel. You'll find a lot of porosity as you're having to get the material so hot for the bead to lay flat. As a result, these welded joints can break. Bolting them eliminates the problem.