Welding anodized aluminum

[HMW]

Anybody with any experience welding anodized aluminum? I have welded lots of aluminum things but never anodized. Some that I have looked at looks like the weld is painted with something. What do they "paint" it with. Almost looks like primer but I'm sure thats not what its, it matches the anodized aluminum pretty well. Also, any info on the welding process would be helpfull.

Thanks

[yorkiepap]

Hey HMW,
Been welding aluminum many years now. Anodizing is simply an electrolytic process that adds a protective coating to the aluminum. To get the best welds, the anodizing should be removed with a flap sanding disc (40-60grit) on the welded areas. 4043 will give the closest color match and 5356 is close. The alum. then can be re-anodized, if necessary, or if cost-prohibitive, coated with a clear acrylic coating....Denny

[TS-Off-Road]

I have known a few fabricators that after grinding off the anodizing would weld the part then use silver pray paint to coat it afterwards. Maybe it is just paint on the welds you see.

[paulrbrown]

The problem with 4043 as I understand, is if you "re anodize", it will turn black. I have not personally done this, but have read this in many sources. I would imagine you need to increase the positive side of the wave for better cleaning action to remove the oxide coating better. Hope this helps, Pual

[HMW]

Yes, i've been told that 5053 is best if you are going to anodize it. What I have seen is towers that already are anodized and have been welded. I guess you can bend the stuff with out the anoidizing cracking. The welds were definatley made after it was anodized. Maybe it is a clear paint on the welds, it looks good. Also I have read you dont need to clean off the anodized, but can weld right through it. Also read about using a on/off switch on the torch for this process. I have a foot pedal now and have seen thumb controls but not and on/off switch. I see I'm going to have to find some scrap to play with. I recently extended the pedestals on 2 boat seats. I had to sit in teh floor of the boat with the pedal under my leg, worked Ok but thumb controls might be easier I dont believe they were anodized as it welded pretty easy. Maybe a clear coat like wheels or something but not much. I painted the weld with "aluminum" colored rustoleum paint and looks pretty good. of course they are under the seat so you really cant see them very well, but still didn't want the weld to corrode. The tower in this boat is awesome looking.

Thanks for the comments

[paulrbrown]

hmw, if you set the welder to the max amp you want, you can use the thumb control as an on/off, just go all the way with the switch...Paul