Welcome to the board. :cheers:

The post corrosion is easy to remove with either a dry metal scrubbing pad or better yet.. a wire brush. To stop the corrosion from re-forming, buy a set of anti-corrosion terminal pads at your local auto parts store. Also, don't forget to remove the corrosion from the battery clamps as well.

:thinking: The second issue sounds more like a drain on the electrical system.

Given the age of your car, I'm suspicious about the health of your alternator. If it's not putting out sufficient voltage to recharge the battery as you drive, a new battery will lose charge over time.

Remove the corrosion first and see if the car starts. If not, I'd remove your alternator and have it tested at Auto Zone or some other shop to ensure that it's operating to spec.