316SS replacement for high temp salt spray 1

[CajunCAD]

I have an oilfield application with 316SS & 17-4Ph H1150D components. Our customer has cited corrosion & pitting problems with 316SS in the high temp (300F - 500F) salt spray environment and requires a material change.

The 316SS components are 1" AutoClave Medium Pressure (20K) fittings (coned & threaded nipple, gland nut, collar) and a 1/4" medium pressure angle valve with nipples, gland nuts, and collars. These components are connected to the 17-4Ph body.

We are looking at changing the 1" & 1/4" nipples to either 725, 2205, or 2507. Based on the AutoClave Material vs Pressure & Pressure vs Temperature charts HC-276 is the closest replacement for the fitting parts & the 1/4" angle valve.

Does anyone have any other material recommendations?
Should I be concerned about gall potential between any of the components/materials I mentioned?

Thanks for your assistance.
Louis

 

[BobUXL]

You may want to examine a duplex or super duplex alloy for this applications. Check out

http://www.ugine-savoie.com.

They have several duplex alloys that could suit your needs.

 

[mcguire]

Also check with AvestaPolarit. They have an excellent website and interactive technical service.

 

[CajunCAD]

I spoke with a Sandvik tech rep familiar with my company's products and he recommended against 2205 & 2507 as the heat range could make them vulnerable to pitting. He recommended that I pursue a nickel based alloy.

Research continuing....

 

[mcguire]

That was honest of him. C-276 sounds like the ballpark for hot salt spray. Iron based alloys aren't up to that duty.

 

[grandprix]

Mcquire is right. C276 will certainly do the job for you. As a lower cost alternative you may want to try a Nitronic 50. It has better corrosion resistance than a 316 or 317 stainless and is often used in salt water applications. It also has better galling properties than the 316 you are using now.
I am not sure how the temperature range would affect the corrosion resistance. You could probably get some info on that from the Nickel development institute (ww.nidi.org).
Electralloy has all kinds of info on this alloy

http://www.electralloy.com/Nit_50.PDF

 

[mcguire]

At 20% chromium and 2% moly Nitronic is only marginally better than 317. This isn't enough for this application.

 

[CajunCAD]

Thanks for the continued assistance. After further discussion the temperature range has come down to 200F - 300F.
Sandvik still recommends against 2205 & 2507 as this temperature is above the critical pitting temperature of 175F.
Still evaluating options....

Louis

 

[unclesyd]

Is the environment oxidizing or reducing? C276 does not like an oxidizing environment. You are in the range of Cu-Ni alloys at 200°F-300°F.

 

[CajunCAD]

Oxidizing

 

[unclesyd]

You are going to have to be careful with C276 under oxidizing conditions. Depending on the media a few degrees in temperature can kill you. We had a very large C276 HE (vertical condenser) operating in a "slightly reducing" media and doing quite outstanding. There was a process change that put the stream in a “oxidizing” condition. Within 1 week we lost the HE due to corrosion of the tubes in the tube sheet area. We completely dissolved the tubes in this area, while immediately below the tube sheet corrosion was nil. $500,000 down the tubes. No pun intended.

 

[stanweld]

You may wish to consider some of the "6Mo" type alloys with your lowered service temps - UNS N06007, N06975, N06985, N08031, N08367, N08925, N08926 etc.