Sealed rolls, or what's been sitting in the gun? Depends on how it has been
stored, humidity, shop environment with airborne solvents, airborne paint
fumes, exhaust fumes, several factors. All aluminum is notorious for
oxidation, and it oxidizes rapidly even in good air.
Look at it. Is it sealed inside plastic? Mainly look for white powder.
That's the oxidation you don't want. If it is a critical application, you
might want to start with new wire. I'd try some test coupons first.
CAREFULLY open it up and tie one end to something. Put a dowel through the
center holes and walk until about 10-20 feet come off. Have an assistant
help you. One hold the spool and dowel. Take a dark rag and run down the
cloth pinching it between two fingers and look for white on the rag. That
should tell you a lot if there's some there, just not visible through the
plastic. If that comes up clean, I'd say it's good to go. If it's white,
you got oxidation. Carefully respool the wire by turning the spool and not
wrapping the wire around the spool. Do it carefully because if you kink it,
you might want to just toss that piece. If it's noncritical, and there
isn't obvious excessive white powder, I'd run it if I got some good coupons
on test welds. Band saw coupons to look inside.
HTH
Steve