Cast aluminum problem

[metalmater]

Hello,
I am trying to weld a cast aluminum side cover for a custom bike. I have welded cast before with much sucess, but this one is a little different.
I am plug welding some holes in the cover and need a perfect finish
for chroming. The problem I am having is I just can't get away from some
pitting around the weld perimeter. I have tried "cooking out" the impurities with the arc and then adding my filler. But when I grind the weld there is always some monor pitting. I have tried different fillers, settings on the arc "dig"and "clean". (Syncrowave 250dx) with no success. I am beginning to believe it is not reasonably possible to get a smooth, chrome ready finish on this thing. Any advise would be appreciated. Thanks....Mike

[Aerometalworker]

Hello,
I am trying to weld a cast aluminum side cover for a custom bike. I have welded cast before with much sucess, but this one is a little different.
I am plug welding some holes in the cover and need a perfect finish
for chroming. The problem I am having is I just can't get away from some
pitting around the weld perimeter. I have tried "cooking out" the impurities with the arc and then adding my filler. But when I grind the weld there is always some monor pitting. I have tried different fillers, settings on the arc "dig"and "clean". (Syncrowave 250dx) with no success. I am beginning to believe it is not reasonably possible to get a smooth, chrome ready finish on this thing. Any advise would be appreciated. Thanks....Mike

Mike,
If its a harley, for years they used zinc based alloys for their primary and cam covers.
-Aaron

[Bodybagger]

I use balanced AC sinewave 1% zirconiated tungsten and 4043 filler. Never develop a puddle. It will sputter out at the edges just as you described. Have the filler rod right there and at the first hint of melting, jab the rod in. It is very touchy. Also needs to be super clean.

[wrenchnride247]

Welding used parts from engines can be tuff. The hot oil just sucks into the part over time. Baking in an oven at 400 deg. for an hour can help "cook" some of the oil out. (make sure to have good venting)

If the pits are not real deep the plater can fill with copper (they coat with copper first anyway) then buff before chrome.

[metalmater]

Yeah it is a Harley. It is a final drive cover so it is not immersed in oil. Maybe I'll give the "cold" weld process a try. Wrenchnride, can the chromer fill the pits in aluminum with the copper? I could see steel but not sure if they could get copper to adhere to the aluminum. Thanks for all the replies. It is appreciated... Mike

[Aerometalworker]

Yeah it is a Harley. It is a final drive cover so it is not immersed in oil. Maybe I'll give the "cold" weld process a try. Wrenchnride, can the chromer fill the pits in aluminum with the copper? I could see steel but not sure if they could get copper to adhere to the aluminum. Thanks for all the replies. It is appreciated... Mike

Mike,
What vintage part?? I used to weld quite a bit on primary covers and had similiar issues with some. If we did have any tiny pits left the plater would just buff them out in the copper. The copper is the first deposit , followed by nickel , buffed out, then chrome. This is at least how the good shops do it. We always sent ours to Browns to have it done. Man that was a few years ago!
-Aaron

[wrenchnride247]

Yes, they can use copper. (as Aerometalworker said)