Passivation

[dtreacy]

I am extending the purified water loop on a site.
My plan is to fabricate up the various spools in-situ and tie them into the loop at a later date.
My question is this.
Is it acceptable to fabricate these spools now and leave them sit for a couple of months without passivation.
What are the implications of such a practice. (I’m thinking potential corrosion issues in the HAZ and weld, but I do not have any idea as to what the maximum length of time a weld can be left without being passivated).

Can anyone shed light on this,

Thanks
Daragh

 

[MedicineEng]

dtreacy:
I believe that you are speaking about SS316L. I don't believe that you have any problems with the weldings, providing that your storage conditions are appropriate. I would suggest you to put the pipes in a place away from acid vapours and segregated from other materials, like carbon steel.
Hope that helps.

PR

 

[dtreacy]

Many thanks.
The pipes will be capped and purged when in situ. The environmental conditions are indoor in dry hot service voids any from aggressive / corrosive vapours.

Regards Daragh

 

[quark]

Generally there won't be any problems but why can't you passivate them offline?

Regards,

 

[dtreacy]

Ultimately they will be welded into the loop, if they were passivated offline there would be a requirement for a final passivation once they were welded in place.


Regards
Daragh

 

[HEC]

Daragh

All stainless steels will auto passivate, ie form a passive layer in atmospheric air. The strength and uniformity of this passive layer is the only reason to chemically passivate. What treatment are you using for passivation. I also agree with Quark, passivate off line then repeat when welded into the line.

Regards
HEC