I've had this problem for a good 5 years or more. Never figured out why this keep happening.
I'd say it happens in a month or two. Right terminal seems fine. Maybe it's the battery itself? Seems to work fine. About once a year the car won't start, and cleaning this off solves the problem.
Today I noticed it before it became an issue. Just wondering why it happens so fast?
I was looking for a Corolla newgroup, but was unable to find one. Post a link if you know of one.
Thanks