Baked Aluminum Pot

OK, after doing much research on HBT, I just ordered a Bayou classic burner with an aluminum pot. When it came in, it was dented, so they sent me another one ... so now I have 2 30 qt aluminum pots.

Well, I boiled water in one to build up the oxide layer ... all went well. i decided for the second pot to save the prpane and bake it at 350 for 10 minutes. After 10 minutes I saw no change in the color of the pot, so I left it for another 10, still nothing. Did I miss something here, or is there some kind of trick to doing this in the oven?

I would think 20 minutes of contact time wouldnt be nearly enough to get the pot hot enough to get this effect. I could be wrong, but I thought I have read that it can take several hours