×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Material selection for sodium chloride stream

Material selection for sodium chloride stream

Material selection for sodium chloride stream

(OP)
I need to purchase some thermowells and pressure instrument diaphragms for pipe which has a saturated brine solution at 280 degF that is about 25 wt% NaCl? Any  concerns with long-term corrosion issues if I use Hastelloy C material?  Would titanium be a better choice than Hastelloy C? Where can I find corrosion rate information for NaCl and these materials?

RE: Material selection for sodium chloride stream

What else is in the solution?  What is the pH?
There are lots of good sources for corrosion data.

Alloys such as C-22, 59, and 686 may be suitable.  We will have to check corrosion data.
Regular Grade 2 comercially pure Ti is probably not a good choice.
The pH is very important.

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection
http://www.trent-tube.com/contact/Tech_Assist.cfm

RE: Material selection for sodium chloride stream

If the pH is above 3, then one of the titanium grades will be suitable.  Crevice corrosion can be a problem for Grade 2 at temperatures above ~ 85 C at lower pH.  If there will be any oxidizing species in addition to the NaCl brine, then the passivity of Ti will be extended to lower pH.  Grade 12 and Grade 7 have increasing resistance to crevice corrosion relative to Grade 2.

RE: Material selection for sodium chloride stream

(OP)
The pH is 10.5 to 11.0.  Other components in the solution include Ca (~5 ppm), Mg (~1 ppm), SO4 (~500 ppm) and Si (~3000 ppm)

RE: Material selection for sodium chloride stream

At this pH, even grade 2 titanium will perform well without crevice corrosion issues.

RE: Material selection for sodium chloride stream

280F, pH >10.5 and 25% NaCl
I have data from 21% NaCl+ 5% CaCl+ 1% MgCl at 224F (boiling) and a pH of 6.8.  In crevice testing for 72 hours there was no corrosion on AL-6XN, AL 29-4C or Ti Gr2.

Do you have any concerns about Si scales forming?
Be careful using Ti thermowells in cross flow.  They have a lower modulus than Fe or Ni alloys and they will vibrate a lot more.

If it were me, I would go with a Ni-Cr-Mo alloy just for saftey.

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection
http://www.trent-tube.com/contact/Tech_Assist.cfm

RE: Material selection for sodium chloride stream

The lead time on titanium, according to Allegheny, is two years. Similar with other high corrosion resistant alloys.
They are suggesting using alloys like 29-4C and Al6Xn, not as a better alloys, but as a deliverable ones.

Michael McGuire
http://stainlesssteelforengineers.blogspot.com/

RE: Material selection for sodium chloride stream

I am not sure that AL-6XN or AL 29-4C offer enough margin in corrosion resistance for me.
The Ni alloys (59, 686, C-22) are available.

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection
http://www.trent-tube.com/contact/Tech_Assist.cfm

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources