Prepping aluminum for TIG welding

In another post, JohnT mentioned he thought the AC portion of the aluminum TIG arc would clean the aluminum. I also harbored that same thought-so my question is, when we see example welds on videos at WT&T, for instance, the explanation of AC balance makes it a point to show the frosty cathodic cleaning zone. What is the difference between those welds, which break up the aluminum oxide layer and produce the frosty clean zone, and my welds, where I have to use a flap disk to get to bare metal? Is it the alloy of aluminum, or maybe the amount of oxide that has built up?

For best strength the metal should be cleaned. That said the longer the aluminum is exposed to humidity, chemicals, and air the thicker the oxide layer becomes. On new alum. the layer can be cleaned to an acceptable amount by the cleaning action of the arc but for top strength it is good to clean it anyway.

Got ya- thanks!

To be clear even a piece of alum. that had the oxide coating cleaned off of it one day should be cleaned again if the welding on it is not completed within the same day . I personally would not clean it again unless it was a critical part that needs top strength, like an airplane part .

I tig a ton of aluminum. Use an Everlast 250 EX.

I use a wire wheel which is only used for aluminum and wire wheel the areas I am about to weld. I then use a product called Arcare Protex Aluminum Cleaner. I just pour a little on and spread it around with a small rag. I then let it dry. It keeps the aluminum from oxidizing. When I am ready to weld, I use a bit of Acetone to clean it up and I also use a bit of Acetone on a rag and run my aluminum tig rods through it. You will be surprised at how dirty those rods are!

After cleaning all that up like that, you will get sparkling clean tig welds that have no black soot in them at all.