Remove the MPU board from the machine and remove the batteries. Clean it with 1 part vinegar 1 part water and use a tooth brush. The vinegar will neutralize the acid. When clean rinse or spray it off. Dry it off with a hair dryer set to cool to get as much standing water off. Then let sit in a dry area for at least a day. I have saved multiple boards doing this. Often never had any damage after cleaned. The furry acid stuff is conductive and can short out things. It will continue to eat away your board if not removed. That is why you need the vinegar.

Your worry is well founded. Battery damage is an invisible killer. I would send the board out for repair and have it properly cleaned and have the affected components replaced. There are several people who post here that can do the repair properly (Chris Hibler, John Wart).

Marc

If the board is working and you scrub it down as I mention above no need to send the board out for repair or replace the parts.

Alkaline is a base, not an acid.

You need to properly repair it. It's like rust, it never sleeps and it will come back when you least expect it.

Remove anything it has come into contact with.

Sand or grind the alkaline out of the traces to bare copper

Seal the board and rebuild.

I guess I just get use to the term acid. However Vinegar is an acid that can be used to neutralize the Potassium Hydroxide, or KOH.

And your battery uses Potassium Hydroxide. The boards I cleaned with vinegar are still clean many years later.