A2 is a martensitic tool steel, not a "stainless steel". It will rust almost instantaneously (less than 5 hours) when exposed to salt spray unless it has some type of corrosion resistant coating on it. You will need a different alloy or some type of coating if there is a requirement for significant hours of exposure to ASTM B 117 with no red rust.
Is it possible this is regarding A2 stainless steel fasteners according to ISO 3506? If so, then they can withstand neutral salt spray for a long time with only minor pitting.
This format can lead to poor assumptions like mine. When consulting on the phone I knew who I was talking to; "Stainless Steel" meant 13Cr to production , SS meant 304 to refinery, and SS meant 316 to chemicals (and SS meant something expensive and shiney to management).
Properly produced A2 fasteners shouldn't produce visible red rust for a LONG time during a neutral salt spray test. If it does, then it is due to iron pickup from forming/cutting/etc. This test method isn't suited for testing stainless steel.
Regarding standards, I would review corrosion standards like those from ASTM and ISO:
As CoryPad stated, salt spray testing is not really used to test stainless steel fasteners like ISO 3506 A2 or A4. However, here is one example of some testing by a fastener manufacturer showing the corrosion resistance of Type 304 (ISO 3506 A2) after salt spray testing:
