Guys dont over think this, its as simple as my MODEL A FORD.....
Remove the bolt and cable, sand down the frame around the thread hole and top of thread ring...if you have a washer, sand both sides then sand both side of the negative wire end loop, this is to get off all the oxidation, then sand the flange or lip under the bolt head facing down....Do we get it , everything in contact to the frame must be spotless........
Old trick, once you tighten everything down and its done...follow me here.....
Paint over ,YES PAINT OVER THE ENTIRE NUT /WASHERAND FRAME FROM ABOVE ...Why ? it seals out the oxidation...........
Use clear on a brush or black to match the frame.......
Then you are set for decades.....
Other method is to use a star washer under the cable to frame and it works, buy then its just more jewelry under the hood....good luck gtjoey1314