The receiver is anodized aluminum. Unless you break through the anodization, it's not going to corrode. To get proper adhesion you need to degrease the flat of the receiver with something like high concentration isopropyl alcohol (99.9% is readily available) which will not only help remove grease, oil, and other contaminants but will get rid of water, too.
The glue on the velcro won't remove the layer of anodizing on the surface of the metal.
It isn't likely to remove cerakote either...but if you want to be sure you can apply a heat gun to soften the adhesive and remove it easily.
Take a piece of cardboard and cut out a template of the receiver. Make sure you leave room for the trigger plate pin to be removed.
Cut a section of the loop material to match the cardboard template.
Degrease the flat of the receiver thoroughly. I usually give it a good wiping down with isopropyl alcohol and call that good. You can go the extra mile with some Dawn dish soap and water, then dry, then hit it with isopropyl alcohol if you want.
Then peel the backer off your velcro section and apply.
Attachment 80790