Magnetic 316 wire

[johnamross]

I have some new rigging on a boat which is supposed to be 316 but it is moderately attracted by a magnet and some individual strands are showing surface corrosion throughout the length of the stays.

Anybody come across this or got any clues?

[Brion Toss]

Hello,
While it is possible for 316 to be, or to become somewhat magnetic, doing so involves either complex or crappy metallurgy. Most likely the latter. You might simply be seeing the results of a little bit of impurities, but no way of knowing. Since you are paying for 316, and since it is supposed to be austenitic, it really should be non-magnetic.
Fair leads,
Brion Toss

[johnamross]

Thanks Brion, That is what I suspected.

[Dave Mauney]

316ss can be made mildly magnetic by cold work. This happens in wire drawing. The corrosion spots can be contaminates from the drawing die. As Brion suggest the presences of rust spots could also be due to excessive inclusions (crap). On way to check the wire you have is ask vendor for production lot chemistry report and compare to ASTM specifications. Hope this helps some.

Goodwinds
DaveM

[Douglas]

Ahoy John ,,, getting good quality wire is harder than you think .

Each batch of raw wire before it is wound into 1 X 19 , can be suspect .

If you have only one outside strand showing corrosion , ( I think it is called , "Barber Pole" ) ,,, like rust corrosion , would you open up the strands to inspect the core wound wires , too , or would you assume that there may also be a corroded wire in the core windings , as well ?

I found that Barber Pole rusting effect on my 316 SS 1 X 19 rigging wire , too , but cleaning the outside with pickling paste (nitric / hydrofluoric/ phosphoric acid combos) that cleaning did not go into the core wires,,,,, eventhough the cable looked fine , ie: bright and no rust , on the outside ,,,, later I found out the inside core wires were v rusted , Ouch !

There is v good reason that knowledgable surveyors recommend to replace all SS structural fittings after 10 years , use , in warm salt water environments .

[johnamross]

The Mill Certificates from the Chinese supplier show it is 316. We are going to send off samples for chemical analysis. I guess if that comes back normal the client will have to accept it.