Viewing McMaster-Carr to compare key-locking thread inserts and helical style.
Found antiseizing, 18-8 stainless steel for helical inserts.
Anybody have experience with antiseizing helical inserts?
Stainless Steel Threaded Insert Material Types:
*18-8 Stainless Steel Offers excellent corrosion resistance; it may be mildly magnetic.
*Antiseizing 18-8 Stainless Steel Lubricated for gall resistance. Galling, also called seizing, is when two metals stick together and cannot be easily loosened. A combination of nonmagnetic 18-8 stainless steel, manganese, nitrogen, and silicon reduces friction to minimize wear with no additional plating or coating required. Compatible with stainless steel fasteners.
*316 Stainless Steel Has better corrosion resistance than 18-8 stainless steel because it contains molybdenum, which increases resistance to chlorides and sulfates.
I placed this discussion in exhaust system. Consider antiseizing helical inserts to repair a SPRINT exhaust manifold. Don't think there is enought edge distance at "exhaust pipe header flange" to use key locking inserts. Key-locking insert for M8 x 1.25, requires M12 or 1/2-13 tap hole to install insert.