my understanding is that grade 8.8 fasteners are about as good as you can do for a muffler or corrosion resistance.
however, I see higher grade numbers like 10 - is there a much better grade to get for e.g. the exhaust system? what about copper?
UPDATE: thanks for this interesting response - so the term “Stainless” has to do with the plating which is a whole other question, but is the grade in fact unrelated to the plating in theory? Note that what I am asking leaves possible for certain grades to be found “usually” with some type of plating, but only for some reason unrelated to grade.
another question is what does grade say about the alloy? e.g. are copper nuts still available in any grade? Obviously I need to take the info from this thread and search around a while…