# Welding aluminum truss in dock



## rdy2go (Apr 18, 2009)

I have a 40' dock, with aluminum trusses and one of the zig-zag rod ends has broken loose at the weld point. The dock is now outside of the water, up the hill, and I am wondering what is the best way to take care of it. 

Would it be easy for a metal shop to make a call to fix on site? I am not sure what is involved in aluminum welding nor how common it is. If so, would it make a difference to weld it on the hill or once is dropped on the water? The truss would be inches above water.

If I have to take it to the shop is no minor work, I would have to put it on the water, build two A frames out of lumber and then remove the section, take it up the hill to the shop ... not fun. 

Any ideas would be appreciated


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## nap (Dec 4, 2007)

portable welders capable of being used on aluminum are commonplace.

In the water? no way!! 

Unless there is a reason to not have it out of the water, leave it out of the water.

get out the phone book or talk to friends that may be able to recommend a weldshop. Give them a call and explain what you have. Shouldn't be a problem.

One thing you did not say is how far to the nearest power outlet. That could make a difference if the shop does not have a generator powered TIG welder.


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## Ron6519 (Mar 28, 2007)

rdy2go said:


> I have a 40' dock, with aluminum trusses and one of the zig-zag rod ends has broken loose at the weld point. The dock is now outside of the water, up the hill, and I am wondering what is the best way to take care of it.
> 
> Would it be easy for a metal shop to make a call to fix on site? I am not sure what is involved in aluminum welding nor how common it is. If so, would it make a difference to weld it on the hill or once is dropped on the water? The truss would be inches above water.
> 
> ...


You weld with an electric current. Would you stand in the water with a live electrode in your hand?
Ron


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## rdy2go (Apr 18, 2009)

Thanks for the answers. Yes, I will have to call a few shops. As I said, I am not familiar with the equipment used, It may have been torch based. I understand the electric concern. The spot to weld would be about ten inches from the plastic deck surface and above the water level. It would be a matter of kneeling on the deck. I would never think in going with waders to weld this. But I hear you.

Any idea of the electric service needed? There is a duplex receptacle close enough, I assume 15 A, but with a long run to the house, and there is also a service for a small lake pump, not sure what is there, I will have to check. We got the house at the end of the summer and has been under snow until two weeks ago, (the wonders of Minnesota), so I still have a lot to learn about it.


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## nap (Dec 4, 2007)

Ron6519 said:


> You weld with an electric current. Would you stand in the water with a live electrode in your hand?
> Ron


actually, there are folks that are underwater welders.









It is just that the typical neighborhood shop is not going to do it this way. 
------------------------


as to the power available;

you will need to speak to the specific shop to determine what they need. Long runs can present a problem. 

There are welders that would operate on a 15 amp 120 volt power but if the specific shop has such equipment is the next question.

You'll have to call around to see what anybody has available in your area.

Chances are they are going to use what is commonly referred to as a TIG welder (TIG; tungsten inert gas) but is more properly referred to as GTAW welding. (gas tungsten arc welding). It used to be commonly called heli-arc due to the type of shielding gas used (helium but more commonly now- argon or a mix of several different gasses including helium and argon)

this process uses an electric "torch" to liquify (melt) the base metal and the filler rod. It uses the inert gas to shield the weld from atmospheric gas (especially oxygen, which causes oxidation; bad thing in welding).


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## majakdragon (Sep 16, 2006)

Call a welding shop that advertises Mobile welding service. They will have the machine on the truck and not need any power source from you. It can be welded with stick, MIG or TIG.


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## Wildie (Jul 23, 2008)

Aluminum can be welded with oxy-acetylene also!
When I was in the airforce, I welded aluminum on aircraft all the time!
Its just easier with electric!


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## nap (Dec 4, 2007)

> Aluminum can be welded with oxy-acetylene also!


never known anybody to weld aluminum with gas. Braze; yes. weld; no. The characteristics of aluminum make it difficult, at best. Melting temp of aluminum is only around 1200º F but the melting temp of aluminum oxide is over 3000º F. The surface of the aluminum is aluminum oxide so the subsurface melts long before the surface will. That can cause problems with welding with gas due to the fact gas does not provide enough btus to heat the surface fast enough to prevent this.

GTAW is the preferred method. It produces a better weld than any of the other mentioned methods and is easier than most and the equipment can be less cumbersome than any except a SMAW welder.


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## Wildie (Jul 23, 2008)

nap said:


> never known anybody to weld aluminum with gas. Braze; yes. weld; no. The characteristics of aluminum make it difficult, at best. Melting temp of aluminum is only around 1200º F but the melting temp of aluminum oxide is over 3000º F. The surface of the aluminum is aluminum oxide so the subsurface melts long before the surface will. That can cause problems with welding with gas due to the fact gas does not provide enough btus to heat the surface fast enough to prevent this.
> 
> GTAW is the preferred method. It produces a better weld than any of the other mentioned methods and is easier than most and the equipment can be less cumbersome than any except a SMAW welder.


 The trick is to get rid of the oxide using a flux! Aluminum was always welded by gas until modern welding equipment was developed after WWII.
I always thought of welding aluminum with gas as similar to sticking a grilled cheese sandwich together.
The aluminum the cheese, the oxide the bread!


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## rdy2go (Apr 18, 2009)

Since we bought the dock direct from factory in September, we just called the manufacturer to get a welder reference. They said, no problem, the same guy that installed it, can repair it once it is on the water. They said, it is better to drop the dock on the water because the repair can be done at any time from above the dock, and that gives the guy flexibility to stop for the repair next time he is in the area.

I guess this one is on its way to get solved. Thank you for the answers and the insight into the welding process.


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## brokenknee (Dec 13, 2008)

Post back once you get it fixed and let us know the method they used.

edit: If you just purchased the dock last year I would think it should be repaired for free, even if there was no stated warranty.


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## rdy2go (Apr 18, 2009)

Yes, I though about the warranty but unfortunately, the rod is not only broken from the weld but also bent. I was thinking that it may have broken off when the dock was pulled of the whater up the back and the hill, wich is pretty traumatic for the thing, but after noticing that is is bent, I tend to believe that some time we did run the pontoon into it. I will try to talk the guy into passing the bill to the factory, but I am not holding my breath.


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## brokenknee (Dec 13, 2008)

Did it bend any other part of the dock?


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## rdy2go (Apr 18, 2009)

Sorry, I have been busy and could not get back to this. I have tried the warranty path, but this is the peak time for the factory and would not get anyone on site for over a month. 

There is another rod next to the problem one that is bent but not broken.

I located the only guy in the area with a mobile MIG welding equipment, but there is no way he can get the trailer down to the lake. The maximum reach from his rig is 25 feet. 

I decided the only option was to take it apart and to the shop, so I called the guys that help me to move the dock in and out of the water and they removed the section in nothing. About a dozed bolts. They will take it to the shop and bring it Monday to reassemble and drop the dock in the lake. 

This one it is being taken care of. Thanks for all the advice and the education on the topic.


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