BillH wrote:
Certainly not dielectric grease, dielectric grease impedes the flow of electricity.

I use good ol Vasoline, been doing it for years and years.
I coat the battery terminals in it.
After cleaning frame ground points to shiny metal I put it on the frame and the ring terminal.

I've never had a corroded connection after doing this.

There are products out there for this but they are very close to Vasoline & why pay more?

All you're doing is to put a layer on the connection to keep oxygen away.