Also, there is considerable debate on hot side aeration. All I can say is that my process introduces a lot of hot side aeration. I have never been sited for oxidation in competition.
Maybe the good folks at Wisconsin can help you better understand that aluminum is reactive.
http://scifun.chem.wisc.edu/chemweek/aluminum/aluminum.html
Just had this happen to me. 5 gallons in the bottom of my keezer. The bummer was I brewed specifically for the Sam Adams longshot competition that I have now missed for the third year in a row.
I haven't figured out what the problem was yet.