Stainless Steel - Pickling & Passivation - Pipe weld inside
Stainless Steel - Pickling & Passivation - Pipe weld inside
(OP)
Dear experts,
My question is, after welding our clint wants us to do pickling and passivation on the welded A312 TP316L stainless steel. But they want to do pickling on the inside of pipe as well (weld area). The thing is we are purging weld from inside until weld is finished and cooled down, so there wouldnt be any heat changes at the inside. And natural chrom-oxide layer could happen easily.
Is this really mandatory? Your urgent response is appreciated.
PS. weld is only from outside, oneside bevel.
Thanks a lot.
My question is, after welding our clint wants us to do pickling and passivation on the welded A312 TP316L stainless steel. But they want to do pickling on the inside of pipe as well (weld area). The thing is we are purging weld from inside until weld is finished and cooled down, so there wouldnt be any heat changes at the inside. And natural chrom-oxide layer could happen easily.
Is this really mandatory? Your urgent response is appreciated.
PS. weld is only from outside, oneside bevel.
Thanks a lot.





RE: Stainless Steel - Pickling & Passivation - Pipe weld inside
Will you be visually inspecting every weld?
If there is no tint at all then passivation only should be good.
There are standards that cover this sort of thing, try the ASME BPE code.
= = = = = = = = = = = = = = = = = = = =
Plymouth Tube
RE: Stainless Steel - Pickling & Passivation - Pipe weld inside
Yes we will visually inspect all welds.
For inside of pipe, isnt natural oxidation is enough, do we need passivation treatment.
Could you give me the section from ASME BPE, couldnt find specific detail for that.
Thanks,
RE: Stainless Steel - Pickling & Passivation - Pipe weld inside
It could also be the Client doesn't trust you welders and needs to be sure you are not ruining the piping. It also depends on the size of the pipe and what type of pickling you might use. Use the search button on top of the page, this topic has been discussed a few times earlier.
Cheers,
gr2vessels
RE: Stainless Steel - Pickling & Passivation - Pipe weld inside
Diameter is varies between 1/2" to 20". Could find specificly for inside weld, thats why I opened a new topic.
Thanks,
RE: Stainless Steel - Pickling & Passivation - Pipe weld inside
If it was in the technical specification or purchase order, yes. Even with good purging practice there could be detrimental effects on corrosion performance and pickling usually creates the optimum surface conditions. On the other hand, if carried out incorrectly, it can do more harm than good.
www.stainlesspickling.co.uk/docs/cleaninghandbook....
Steve Jones
Corrosion Management Consultant
http://www.linkedin.com/pub/8/83b/b04
All answers are personal opinions only and are in no way connected with any employer.
RE: Stainless Steel - Pickling & Passivation - Pipe weld inside
If you have a standard color to work to and you will inspect and document each weld then passivation alone should be good enough.
Yes, you need to passivate, not to form a passive layer but to clean the surface so that it can naturally form a defect free passive film.
= = = = = = = = = = = = = = = = = = = =
Plymouth Tube
RE: Stainless Steel - Pickling & Passivation - Pipe weld inside
Short spools can be pickled by immersion. Otherwise you're talking about a circulating solution process as the only practical option, and that's not easy to accomplish both safely and effectively.
RE: Stainless Steel - Pickling & Passivation - Pipe weld inside
Therefore if there is no oxygen left inside of pipe (due to purging with argon), there is no need to remove thick oxide layer which is the purpose of this practice. Thats why I asked this, because it doesnt make any sense. Is there any other reason that I missed?
RE: Stainless Steel - Pickling & Passivation - Pipe weld inside
The second problem is that the natural passive film will only form, and function correctly on a clean surface. Even small embedded particles of SS or Fe will lead to local corrosion initiation and pitting.
Passivation is a cleaning operation.
Even if you welds are very bright you should do a full system passivation of the finished system to assure optimal corrosion resistance.
= = = = = = = = = = = = = = = = = = = =
Plymouth Tube
RE: Stainless Steel - Pickling & Passivation - Pipe weld inside
RE: Stainless Steel - Pickling & Passivation - Pipe weld inside
= = = = = = = = = = = = = = = = = = = =
Plymouth Tube
RE: Stainless Steel - Pickling & Passivation - Pipe weld inside
You client sounds either inexperienced, has extremely aggressive service, or overly cautious to the point of madness.
RE: Stainless Steel - Pickling & Passivation - Pipe weld inside
Anything darker than a light gold tint on welds is unacceptable in UHP water service.
To do this with backing gas requires a level of care that most people outside of pharmaceutical and semiconductor fabrication have no concept of.
= = = = = = = = = = = = = = = = = = = =
Plymouth Tube