Just a physical key then not a chemical one.
Are you using sandblasting as a generic term or do you mean specifically it is silica blast as opposed to aluminium oxide?
Alan
100-120 grit aluminium oxide grit or garnet is recommended for Cerakote. Here's all the info you need:
http://www.cerakoteguncoatings.com/resources/files/Cerakote-Training-Manual-Web.pdf