Take them apart, wire brush or scrape them with a screwdriver to remove any crud and get exposed metal, then put some dielectric grease on them and connect them
If you do as said you will expose the base metal of the connector and cause additional accelerated corosion.
Also dielectric grease is an insulater and has no place on the contact points of a connector. Maybe the connector will displace the greese, but you can float a battle ship in a 1 molecule thick sheet of water. To think that the grease will be fully displaced probably will not happen
