316L SS - To Pickle and Passivate or to Bright Anneal. That is the question. 1

[hondashadow1100vt]

I am a PE working on a construction project. Our specifications call for all 316L stainless steel piping to be pickled and passivated. Our contractor has proposed one manufacturer that can furnish all the piping for the project, however the manufacturer uses both the pickle and passivation process as well as the bright annealing process to prepare the piping. The manufacturer claims that they cannot furnish all of the piping with only the pickled and passivated treatment. I am trying to make a fact based determination of whether or nor the bright annealing process is technically equivalent to the pickle and passivation process. The purpose of this thread is to request information/insights/feedback on the subject of these two treatments.

I am specifically thinking that a technical substantiation would include the following:
1. What is the intent of the pickle and passivation process? Is the intent of the bright annealing process the same or somewhat different?
2. How is the pickle and passivation process’s effectiveness is measured? What test is available? What data can prove it?
3. How the bright annealing process’s effectiveness is measured. What test is available? What data can prove it?
4. Relative qualitative cost difference (if any)

Thank you in advance for any feedback that you may be able to provide!

 

[MikeHalloran]

Pickling typically comprises treatment with nitric and hydrofluoric acid. Its purpose is to remove the 'brown tint' associated with welding. Brown tint, left in place, severely compromises SS' resistance to stress corrosion cracking, and probably some other failure modes too.

Passivation typically comprises treatment with nitric or citric acid. Its purpose is to remove free iron from the surface of a SS part. The free iron often comes from forming the SS with steel tools. Note that even the most exotic SS is still 60 pct iron, so there will be some free iron anyway. The free iron usually manifests itself as surface rust, given the slightest provocation.

I know nothing about bright annealing except that it makes the product look nice in the showroom.

You can probably find much more, and more useful, information, on outokumpu's or special metals' or any other stainless producers' websites. I suggest you visit all you can find.


Mike Halloran
Pembroke Pines, FL, USA

 

[cloa]

Don't double post.

http://www.eng-tips.com/threadminder.cfm?pid=1529

Use translation assistance for Engineers forum

Note the rules include No Student posting

 

[hondashadow1100vt]

MikeHalloran:
99.9% of this piping will not be welded but rather will be fit together with grooved joints or press fit type joints.
That said, we do have a 316L stainless steel tank on the project therefore I really appreciate the info.
Thank you for the referral to the manufacturers’ websites. I will make some time to look at those sites.
Thank you.

 

[hondashadow1100vt]

cloa (Petroleum):

10-4. Thank you for the advisement. I am still pretty new to this stuff. I'll avoid the double post maneuver in the future. I did it this time because there appeared to be a number of different sub-forums that would be applicable and I did not know which would be best. Nevertheless, you are right. I'll be more mindful in the future.