motor shaft material 1

[NIDinc]

We manufacture a specialty elec. motor that requires the shaft to have good magnetic properties but we also need good corrosion resistance. We've been using 416 stainless steel (7/8" rod). but it is not standing up to the corrosion of the salt water environment.
Question: will 17-4 stainless be ok or perhaps a duplex ss like 2205? How does 430 solenoid grade compare with a 300 series SS?
Thanks!

 

[masieh2004]

Yes. 17-4 stainless steel has better corrosion resistance compare to 416.
You can also use 316L Stainless steel.

 

[NIDinc]

We cannot use a non-magnetic stainless (300 series) because of the way it interferes with the motor electrical flux

 

[EdStainless]

17-4PH is not a good option for seawater service.
You might look at 13-8PH, at least it has some Mo in it.
2205 has much better corrosion resistance, but I don't know if it is magnetic enough for you.
I find it hard to believe that your motor is so under designed that removing a magnetic shaft hurts performance.
The 2205 may be enough, I would try it first.

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[MagBen]

I gave an answer at "Electric motor.." forum.

13-8 may have a little better corrosion at sea water than 17-4, especially in H 950 condition. However, although being better than 430, 416, both 17-4 and 13-8 are still restricted in sea water.

 

[NIDinc]

Thanks for the helpful replies. I consulted with a metalurgist yesterday who suggested that basically I'm screwed. But the best option he thought would be to make the shaft from 430 solenoid quality SS and have it nickel plated. He didn't mention 13-8 but he did mention that 17-4 has poor electrical properties for motors --same with 2205.

 

[MagBen]

what do oyu mean by electrical properties? resistivity? 17-4 can have various resisitivities depending on conditions. solution heat treated condition does have a high reisitivity, but aged conditions have a much lower values.
If keeping in salt water all the time, Ni plating is still not sufficient.