Technical Oxy acetylene welding aluminized exhaust components

When patching together "custom" exhaust parts for various vehicles I often use sections harvested from cars with OEM heavily aluminized exhausts. Lately I've been having problems with achieving fusion with the aluminized parts. Removing the coating with abrasives works OK, but a convenient wire wheel seems to just smear the aluminum. Previously I could "break up" the aluminum coating by manipulating/dabbing the filler rod when the steel was molten, but it seems recently that has not worked particularly well.

On a welding bulletin board someone suggested that the copper coated Oxy acetylene filler rod was part of the problem, and uncoated filler would work much better. I think someone claimed that coat hanger was a great filler for exhaust work, but I am reluctant to start using that unknown stuff even for non-structural work.

Over on eng-tips the common recommendation is dip the end of the pipe in drano etc to eat the aluminum off the pipe.

Is there a quick, easy, cheap magic way to work with the aluminum coating in place?

thanks,

Dan T

 

I do ok with using abrasives, but I don't do much with used pipe, mostly new pipe.

How about baling wire? available at the hardware store. Probably a more mild steel than hangar wire, and has nothing on it but oil, which you can clean off pretty easily. It is a bit thin, though.

 

I have never had any issues welding aluminized exhaust pipes with an oxy acetylene torch.
If you are using regular gas welding rod like a Hercules R45 then there should not be a problem.

The gas rod has a small amount of aluminum added to it as a deoxidizing agent.
I have welded aluminized exhaust tubing exactly as you describe simply by welding it as is, no pre cleaning at all.

Possibly you are using the wrong flame setting, an oxygen rich flame could cause a problem.
Usually a good hot neutral flame will work well.

If you can't master that I would switch to a good solid wire MIG setup.

 

I have always used coat hanger, Another tip is don't adjust torch tip to a fine blue let it fluff a little. Hope that makes sense... Ive been welding the stuff since it came out in the early 80s....John

 

Best to burn the clear off part of the coat hanger first.

 

If you are using pipe off a newer car are you sure it is not a stainless pipe

 

that may be the change also

 

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Pretty sure no stainless. My previous efforts to OA weld stainless have been disasterous creating black crust.
And after grinding off the coating it welds as normal.
The price and online description of the muffler preclude stainless construction too.

 

I've always had good luck with a 4" grinder and coat hanger.

 

Got it. Not an oxidizing flame. Neutral to slightly reducing/carburizing flame.

thanks all

 

I have used coat hanger, as traditional as it gets, was taught how by a real old fart waaaay back in tha day.

 

Old timers never bought welding rod for gas. They always used coat hangers but the steel in them was probably better back in the day. They were much stiffer. There was a flux to use with steel too.

 

I've been using an OA torch off and on for about 60 years or so and I don't think I've ever seen a flux for welding steel with OA.
If there is such a flux and it helps.I'd like to get hold of some of it.