Tips for Basic Filler Metal selection along with some resources for filler metal selection.
Aluminum filler metal chart from Aloctech http://alcotec.com/us/en/support/upload/Aluminum_Filler_Alloy_Selection_Chart.pdf
Washington Alloys Stainless Filler metal chart https://washingtonalloy.com/wp-co...
The Electrode Positive part of the AC arc is what breaks up the aluminum oxide layer on aluminum and allows the puddle to be clean and flow out well.
so let that cleaning action work for you before puddling dirty aluminum.
In other words...Dont puddle too quickly