Stainless steel is still subject to corrosion.
Blackpowder fouling is easily removed with cool or tepid water and perhaps a little soap. Since its stainless hot water will not cause after rusting and will dry faster.
The internal mechanism need not be cleaned every shooting session. But keep it lubricated.
I like to use Window cleaner with vinegar mixed 1 part cleaner to 2 parts water.

If you use Pyrodex or T-7 you better use hot water and lots of it.

Dan