salt corrosion resistance of 17-4 PH

[musashi99]

I’m looking for some information on the salt corrosion resistance of 17-4 PH.
If there is no other scale of comparison how does it compare to 316 (I know 316 is better but how much better)

 

[EdStainless]

What kind of salt corrosion? Incidental exposure? What salts, concentrations, pH, and temperatures (any chance of drying and concentration)?

In general, I consider 17-4PH to be a 17% Cr grade (like 304, 430 or 439) in terms of Cl resistance. For constant Cl concnetration and pH, Assuming htat we are near neutral and near ambiant) the pitting limit on 361 will be about 50F higher than for a 17% Cr grade.

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[musashi99]

We are dealing with sea water. 30 deg-130 deg F.

 

[TVP]

Neither of these grades is suitable for immersion in or constant exposure to seawater.

 

[unclesyd]

I have used 17/4, Aquamet 17, for numerous boat shafts in warm sea water. The only caveat is the boat needs to be active, if the boat is going to be laid up periodically the material is changed to Aquamet 22 due to the propensity of 17/4 to pit in stagnant sea water. All the above with zinc anodes
I have also used 17/4 for the following components exposed to warm sea water.

Rudder shafts, with zinc anodes
Rubber gear pump shafts
Fishing reel components, both commercial and personal.
Chain plates on older boats.
Anchor components.

There is a good galvanic table the PH alloys in the "shafting data brochure" on this site.

http://www.wbmetals.com/

 

[EdStainless]

With good galvanic protection you will be OK, except at the higher temperatures. I am not sure that Zn annodes will give you enough protection for 130F in seawater. That is getting hot for these alloys.

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Rust never sleeps
Neither should your protection

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