How to ID 304 and 316 SS Wire ?

[over40pirate]

I bought a partial spool of rigging wire at a Marine swap meet. How do you tell whether it is 304 or 316?
It doesn't say on the spool

[sigmasailor]

You cannot tell the difference easily. Looks and feels exactly the same.

A chemical analysis is an (expensive) possibility.
NDT companies could use a portable analyzer like a Texas Nuclear.
There is a fluid (ask your local inspection company)that will indicate the difference; I guess it looks for titanium which is added to 304 to make it 316 and seawater resistant.

[GordMay]

Originally Posted by sigmasailor

...There is a fluid (ask your local inspection company)that will indicate the difference; I guess it looks for titanium (sic: molybdenum) which is added to 304 to make it 316 and seawater resistant.

A molybdenum chemical colour test kit will identify the presence of moly’ in 316 S/S, which is absent (or MUCH smaller %) in 304.

[hellosailor]

Stainless Steel - Sorting and Identification Tests

Looks like you can either buy test solution, or find a local welding shop that is sharp enough to have it, and ask them to run a fast test for a couple of bucks.