Crazy that it occurs within a year on a vehicle!! I work in boating industry, and totally "get" it.
Weird in a fresh water application and stray current.
BTW- these are aluminum... how does a non-conductive metal corrode through electrolysis, and how would grounding help? What is actually being grounded? Engine block?
I'm not sure to even guess where to ground this?
https://www.oilburners.net/threads/as-seen-on-the-internet.81690/