GeorgeLlewellin
Well-Known Member
Can some of you experts please enlighten me. Is stainless steel A4 grade the same as 316 grade and what is the difference between A4 grade and A2 grade. Thanks.
Stainless steel grades
- Thread starter GeorgeLlewellin
- Start date
mph
Well-Known Member
As far as I know, A4 is much the same as 316 but A2 is only equal to 304 grade.
If the fixing is under the water or constantly wet, don't even think of using A2 grade, it won't last.
Have a look at this supplier for all sorts of A4 stainless steel fixings, they are based near Southampton but do mail order as well. Stainless Steel Centre
Or if you want more in depth info on the differance between 304 & 316 etc, look here: web page
If the fixing is under the water or constantly wet, don't even think of using A2 grade, it won't last.
Have a look at this supplier for all sorts of A4 stainless steel fixings, they are based near Southampton but do mail order as well. Stainless Steel Centre
Or if you want more in depth info on the differance between 304 & 316 etc, look here: web page
VicS
Well-Known Member
Yes A4 is equivalent to 316 and A2 is equivalent to 304. Both are high nickel, high chromium alloys, with an austenitic structure. The main difference is that 316, which has superior corrosion resistance to seawater, contains about 2% molybdenum.
So 316/A4 should be used anywhere that will come into frequent contact with seawater. The cheaper 304/A2 is fine though for other uses.
More detailed technical info here http://www.worldstainless.org/About+stainless/What+is/Categories/
and far more than you'll ever wish to know here http://www.bssa.org.uk
So 316/A4 should be used anywhere that will come into frequent contact with seawater. The cheaper 304/A2 is fine though for other uses.
More detailed technical info here http://www.worldstainless.org/About+stainless/What+is/Categories/
and far more than you'll ever wish to know here http://www.bssa.org.uk
vyv_cox
Well-Known Member
VicS has covered it. The addition of 2% molybdenum improves the pitting resistance of 18/8 stainless steel but also, perhaps more useful to us, it improves crevice corrosion resistance. It is quire common to use A2 (AISI 304) nuts on A4 (AISI 316) bolts but most other marine fittings are made from at least 316.
GeorgeLlewellin
Well-Known Member
Thanks for your help everyone, those URLs are really useful. George.
