316 SS pipe

[mae1133]

We have a specification that calls for 316 SS pipe to be pickled and passivated. Does the piping purchased in North Amaerica pickled and passivated or is this a special order request?

Thanks,

 

[YLWEA]

If the requirement is for pickle/passivate, you would probably want to do that after the fabrication is complete. Welding and the related operations (wire brushing/grinding, etc.) are likely to eliminate the benefits of any pretreatment where welds are made. By treating after welding you would reestablish optimum corrosion resistance.

 

[mae1133]

YLWEA:

We already have a procedure in place after the welding procedure for pickling and passivating, however, that was not my question. I was wondering if piping purchased in NA already came from the factory pickled and passivated?

 

[unclesyd]

It is usually pickled if required after any hot finishing though some manufactures do bright anneal some sizes. It would be best to check with your supplier or manufacturer as to how they finish their product.

At one time we had facilities on site to pickle and passivate but quit due to enviromental conerns and the lack of benefits from reworking the piping prior to use.

A large local supplier has no passivated pipe in his inventory. The addition of pickling if available is an adder to the price.

 

[YLWEA]

I must be missing something here. This is not a topic I deal with as part of my regular job, but unless the post- fabrication pickle/passivate treatment is conducted only on localized spots on the surface (such as at welds), or unless the components are all mechanically fastened, why is there an advantage to buying pickled+passivated pipe which will then be fabricated by welding or other means? Assuming the entire surface is treated after fabrication, what benefit does use of surface treatment before fabrication acheive?

 

[mae1133]

YLWEA:

I'm not sure if there are any adavantages other than those you indicated, but once again, that was not my question. I am not specifying piping to be P&P prior to on site construction. I am only asking whether SS pipe manufacturer's P&P the pipe prior to shipment?

 

[mcguire]

You cannot be sure that it would be P&P unless it was so specified. I know it isn't done universally.
YLWEA's point is a good one, since any welding done to P&P pipe will drastically lower the pitting resistance. It is possible, YLWEA, to microalloy the 316L to avoid this phenomenon, but this material is not yet on the market.

 

[mikedavy]

Most manufacturers of stainless steel pipe pickle and passivate after the pipe is manufactured. Some manufacturers "bright anneal" small (ie 4 or 6" and smaller) and do not p&p it. However, almost all welded ss pipe is p&p after the manufacturing process.

 

[stanweld]

ASTM A-312 stainless steel pipe specification does not require pipe to be furnished in the pickled and passivated condition. You would have to order this material to be furnished in the pickled and passivated condition to assure same. This is also true for a number of other ASTM pipe and tube specifications, some of which require pickling but not passivating.

 

[quadswift]

The basic answer to your question is NO.
Regards,
quadswift