I have a carbon razor and it had a few rust spots. I think I found teh reaso why.When I shave the handle gets damp I wip as needed. However at the end of the shave I dip the closed razor into the water to rinse it off. After I wipe and clean it and apply a dab of alcohol along the blade. I close the blade and set in down the razor down. This time I waited awhile and opened up the blade for a look see. And what I saw was dew on the front end both sides. What I think is happening is the handle is moist on the inside causing condensation. The warm moisture of the handle moves to the cooler blade edge.

What I'll do for now on is leave the edge open on the shelf and let air dry after cleaning. I hope this will be of help to all..nick