What can you do to the coil/or alternative part of battery compartment, to prevent corrosion?

Change the batteries regularly, Baking soda will neutralize the powdery acid build up.

In a pinch a little Coca Cola works.

Once the electrical part in question has been thoroughly cleaned of ALL corrosion, coat all parts that might develop corrosion with corn syrup. You can use a artist’s paint brush. The syrup will dry producing a corrosive protection coating that can be easily cleaned off with water, should the need arise.
You could also coat the parts with anti-seize lubricant, but it is hard to clean up much less clean out of your clothes. This can be found in many hardware and auto parts stores.
Or use dielectric compound, a clear grease like substance that is used to seal electrical parts, and be found at your local auto parts store.
There are also felt rings that are used on battery terminals to stop corrosion. If required, these can be tied to the electrical part with a bit of wire or cable ties. Also available at your auto parts store.

Use high-quality cells.

Rechargeable batteries are well sealed, should not leak.

I mean before any leak happens, (before start of use).

^^^^^Rechargeable batteries are well sealed, should not leak.^^^^^^

What I said works for new batteries and components as well as used/cleaned.

Oh yeah. Thanks @kritiper.

Now, wonder how to deal with battery compartments that are partly covered inaccessible to visual inspection or cleaning.

Batteries wear out so there has to be a way to replace/service them. There may be no easy way, or the compartment may have to be removed as a whole.
What exactly is this compartment in???

I mean built in compartments. It could be an alarm clock, a stereo system etc. for example. When you remove the cover you can only see half of the compartement. The rest of the compartment is part of the body of the alarm clock.

…Actually the the whole compartment is part of the body of the item, only the cover is removable.

You can always bend a cotton swab to get into tight places to clean.

I guess so. I suppose it’s cost cutting measure that they design it that way.