Repair Boom Vang
Anything, really - aluminum is very soft.
But then the real questions surface:
1. How to attach? Depending on the nature of the fitting and how its used - in tension and/or sheer - you could be better off with a strong stainless pop rivet vs. a stainless fastener which will lack much thread engagement on the boom wall.
2. How to insulate? Tef-gel still seems like the best choice (which is NOT WM''s Tek-gel product) but there are other good choices, too.