Aluminum Wheel repair

I've taught myself to TIG over the last 10 months for the purpose of repairing aluminum wheels for a friend's wheel repair business. I found a good deal on a lightly used Invertig 201 from HTP. I have been scouring the internet and frequent your website nearly every night for information. Aluminum wheels seem to be tricky in regards to porosity and contamination as well as base metal. I'm about to refill my bottle and intend on getting a helium argon mix this time. All that being said, my question is regarding settings. Most of the wheels I see are around 1/4" on the lip where the majority of wheels crack. I've been grinding out the cracks, stainless wire brushing and using acetone to clean. My typical settings are 195 amps, 75% balance and 200hz. I've been using 1/8 ceriated and lanthanated tungsten. I've been using a gas saver setup with a pyrex cup. I'm experiencing discolored and eroded tungsten as well as black specs on top of the bead. Can different settings improve my end result? do I have a shielding gas issue with the electrodes? On a side note, Do I need a machine capable of more amperage?
Your website is great. Thank you very much for doing what you do. This site is a wealth of information. The more time I spend searching the net looking for information the more I realize there are few people out there so willing to help and spend their time creating such an archive.

Thanks much,

Justin T.

-----------------------------------------------

Justin,

if you electrode is getting blue and purple, then you have a gas shielding issue.

its probably the cup.

i tried one out recently and it disappointed me, It did not work as well as a standard #7 gas lens

I think you might swap back to the #7 gas lens setup and also set the balance to 60-65.

I use around 120 hz. and find that 200 hz breaks down the electrode.

Wait until you try the helium mix before you decide to get a bigger machine.

you may be surprised, but you may need a few more amps...just wait and see.

you may also find that 4047 tig rod gives less porosity and flows with less heat,

good luck bro,

jody