Aluminum reacts readily with oxygen to form a thin layer of alumina (Al2O3), which is hard and sticks tenaciously to the surface of the metal. This process is called passivation. Once a passivated layer is formed, it doesn't get any thicker because it protects the base unoxidized metal from reacting further...although you *can* make a tremendous fire out of powdered aluminum. They use such material along with iron oxide to make thermite, which burns hot enough to generate molten iron...it is used to weld train rails together.
Certain materials will react with the alumina and aluminum, namely strong alkalis. As someone who once heard of a dude whose cousin's friend made drano bombs as a teenager, I can attest to the fact that sodium hydroxide (lye) will rapidly dissolve alumina and aluminum (generating heat and hydrogen gas on the way).
One-step or Oxyclean are made primarily of sodium peroxycarbonate. When it decomposes, it releases oxygen just like hydrogen peroxide does...this is what gives you the sanitizing activity. After the peroxide is gone, you are left with sodium carbonate, which is also known as washing soda. It is a moderately strong base...stronger than sodium bicarbonate, but much weaker than sodium hydroxide. If you notice your hands feel a little slippery after washing up with One-step/oxyclean, it's because the sodium carbonate reacts with the oils (which are weak acids) on your skin and turns them to soap. This is a classic test for whether you just got lye on yourself...if your skin is slippery, keep rinsing until it's gone or you will be treated to a chemical burn.
I have not done any tests, but the percarbonate sanitizers will probably not wreck your aluminum equipment if you take it easy. Don't let the oxyclean sit in your keggle for hours, don't boil it, and rinse it off when you're done. Searching the tubes for peroxycarbonate and aluminum brings up a variety of information that does not condemn using them together, but does give some warnings.
If it's an option stainless steel is a lot less trouble because you can use just about anything you want on it. Barkeeper's Friend is oxalic acid, which may eat up your aluminum. Bleach is not great for stainless (it's a long-term cracking problem) but will corrode aluminum (bleach = sodium hydroxide + chlorine gas). Abrasive cleaners (soft scrub, etc.) will scuff the aluminum but probably not the stainless.
