316 or Duplex For A Shaft?

[robbieg]

I'm getting a new prop shaft made up since the old one was suffering from crevise corrosion. I've been offered one made up in duplex stainless steel for almost the same price as 316 stainless. From a quick google it seems as is there is no downside to going down the duplex route (its stronger & more corrosion resistant unless of course anyone on the forum knows different.....

Any views?

 

[Graham_Wright]

There's a few words in the Vetus catalogue about this.

 

[maxi]

Hope all comments are positive, 'cos I've just had a new duplex shaft made and fitted ! Price less than most stock 316 shafts.

 

[vyv_cox]

It's not a material that I have much experience with, but all is mostly positive. General corrosion properties good, strength can be better than austenitic grades, if heat treated. Stability is better but this is rarely an issue in yachting shafts. Crevice corrosion is better than austenitics, although not perfect. I am aware that a lot of offshore seawater pumps were changed to duplex in the 1990s, improved the situation but not solved it. Now being changed to bronze, real bronze, not the cheaper yachting version!

A few reciprocating compressor piston rods operating in chemicals duties have been made of duplex steels, with some success.

Should be excellent for yacht shaft duty.

 

[boatmike]

Duplex has higher resistence to crevice corrosion than 316 and would be my material of choice certainly. There is only one common better material for corrosion resistance and thats monel which is very expensive and lower tensile.
Go for the Duplex. I have used it on many prop shaft applications with full success. No worries.