×
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

SMO254 acidic seawater

SMO254 acidic seawater

SMO254 acidic seawater

(OP)
Would SMO254 Alloy (6-6.5%Mo) be usable, at 40°C in acidic seawater, pH 2.3 and in a very reducing environment? (SO23)

so wz have chlorides (seawaterà
SO2 / sulfuuric qsp pH 2.3

what worries me is SO2, creating a reducing environment

RE: SMO254 acidic seawater

No.
Don't worry about the SO2, it is the pH that will kill you.
For these alloys each 2 pH units below neutral roughly lowers the Cl limits by an order of magnitude.
This alloy will handle natural seawater, 20k ppm Cl and pH 8, and we know that it would still be OK at pH 6.
Then at pH 2 the Cl limit would drop from 20,000 to perhaps 200ppm, or roughly similar to 316 in neutral environment......

At that pH you need either a Ni based alloy (C22/59/686 or go non-metallic (but watch the S02 with resin systems).

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

RE: SMO254 acidic seawater

(OP)
Thank you very much. With resins I am not overly concerned, we have experience resins . SO2
SO2 / sulfites are not good, but that's still OK

RE: SMO254 acidic seawater

(OP)
I am not expert EdStainless, but I still have a question

According to the OUTOKUMPU figure 254SMO looks suitable for pure HCl (1%) at 70°C (0.1mm/year corrosion)
sea water would have about the same chloride concentration.
You said that the acidity would kill me.
So where is the important difference?
Is it because the figure is limited to general corrosion?
Regards
Figure 254.tif uploaded

Bernard

RE: SMO254 acidic seawater

Look at some of the technical papers on the subject.
http://www.outokumpu.com/en/tools-and-downloads/pr...

There is one interesting point, Outokumpu refers to 254SMO as a 6% Mo alloy, this is it's max Mo.
The other nominal 6% Mo alloys such as AL-6XN, 1925hMo, and 25-6Mo all are likely to be 21-21.5% Cr and 6.3-6.5% Mo. These alloys will have PREN in the range of 44-48, while 254SMO is 40-42.

HCl is easy, this is very different chemically from acidified seawater.
Look at corrosion tables (http://tools.outokumpu.com/spt/corrosion/corrstart...) for HCL + iron chloride, or HCl + sodium chloride, those get you closer.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

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