I found the corrosion where the terminal attaches to the battery case. What I assumed was that it was seeping acid between the terminal and case. I didn't see any electrolyte coming out of the caps to get near the terminal Could I be wrong?
It is possible, I have seen that once or twice in the past.
What I usually see is that the terminals were not cleaned well when the battery was replaced or they were worn down to the copper plating (which seems to just attract that stuff.)
I would look at the top of the battery, if you see something that looks sort of like a moist grime; that's most likely off-gassing that's been occurring and could be contributing to your corrosion issue.
What is the CCA, and version of True Start you have in your vehicle (is it a 84month and/or the lower CCA battery compared to the 720CCA unit used in the higher trims?) I see a lot of brand new Toyotas showing signs of off-gassing. Usually it's from owners who do frequent small trips and short drives; it strains the batteries and since many of these newer Corollas, Camrys, Tacomas, 4Runners, ect are usually running batteries south of 550/580 CCA I wouldn't be surprised if it strains the batteries some and contributes to off-gassing/corrosion.
Post Note-
If you are looking for a battery, I'd see if you can find a more "European" style one that has a vent tube vs. caps. I know a few people who run them and since the hydrogen is vented through the tube and away from the top of the battery, they see almost no corrosion. There was one or two brands that I can't think of the name off the top of my head that sold 12v Car Batteries for all makes and models with the same side vent tubes you see in Mercedes, VW, BMW, ect.
AGM batteries also don't tend to off-gas like flooded ones do.
