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passivation of new piping

passivation of new piping

passivation of new piping

I have a very simple question.  Traditionally, when constructing a piping system made of stainless steel (316L in this application), is the internal side of the piping passivated before use.  I know that the outside of the pipe is to be pickled and passivated, but should the inside of the pipe be flushed with some pickling or passivation solution?  This is a general question and not specific to any particular industry.

RE: passivation of new piping

I guess a little background would be warranted based on the answer by Mr. Jones.  We are building a polymer injection facility to inject polymer and water into existing oil wells.  So, the piping we built was for a water and polymer mixture.  Neither the water or polymer should be corrosive.  So to answer the questions above:
a) The fabrication quality control is very good.  Full visual inspection during fabrication, radiography and hydrotest after construction in accordance with B31.3 requirements.
b) There really should be nothing going on inside the pipe except transferring polymer and water from the injection facility into the well heads.  Keep in mind, this polymer basically makes the water a bit more viscous.
c) Consequence of corrosion would be a leak in a moderatley high pressure line (approximately 50 bar).  Since there are no toxic chemicals, hydrocarbons, lethal implications or anything similar, the risk of a release is very minimal.  Remember, this is in essence water lines.
d) We are working off customer specifications which required external cleaning of the welds, but nothing mentioning internal passivation.
This whole situation is because of corrosion we are seeing in the pipes due to water which was left in the pipe for several months.  After testing some pumps and equipment, we did not drain the water.  The water had some chlorides and H2S, along with other chemicals typical with well water.  The pipes sat with water in the hot Middle Eastern sun (Oman) for upwards of 7 months while another portion of the plant was being constructed.  Over time, the pipes developed pits which worked their way into holes.  Metallurgical review has stated this is typical of fresh water contamination in stainless steel and even if the pipes had been internally passivated, the leaks would still have occurred.  
The basis for my question is because there is specualtion that the construction company should have passivated the pipes internally.  They claim that it is not standard practice unless it is required by specification.  For example the food industry or in the service of a specialty chemical.  What I'm trying to do is take blame from the construction company and assign it to where it should exist, with the company not following preservation procedures after commissioning and testing of equipment.  I was hoping to gauge a sampling of construction procedures to see how often internal passivation is done.  For the record, in my 21 years as a quality manager in large construction projects, I have never passivated internal pipes, nor have seen it specified.
Regards gentlemen.  Any input would be appreciated.

RE: passivation of new piping

I aggree that the corrosion would have happened regarless of passification, the blame clearly lies with the people who left the stagant (un-inhibited) water in the line. A very poor practice indeed.

RE: passivation of new piping

I work in the water industry.  Our practice is the following:

(1) We generally use 304L or 316L when welds are involved.
(2) Since steel tools may have been used in production, we passivate in and out.
(3) Even though the L grades tend to minimize the possibility of iron carbide precipitation at the grain boundaries, it's better to be safe and take care of it.

RE: passivation of new piping

If it's the Marmul polymer flood project try taking a look at PDO ERD-84-01, or SP-2051 as it has now become, and the related Shell DEP

Steve Jones
Materials & Corrosion Engineer

RE: passivation of new piping

Yes Mr. Jones, it is indeed the same project.  We have reviewed the specs with PDO personnel and have all agreed that in this application, there was no need for internal passivation and it was not part of the agreed upon method statements.  We're just trying to do a little damage control for the construction company who is facing scrutiny at this point.  Sounds like you have heard of our problem (which is being replaced as we speak).

RE: passivation of new piping

Well water will often contain both iron reducing and sulphate reducing bacteria that will hasten the penetration of the pipe wall by pitting process with the bacteria helping.

As stated above SS piping doesn't like exposure to stagnant water especially contaminated with or without the above mentioned bacteria

RE: passivation of new piping

as a general rule SS is always passivated in order to avoid any possibility of corrosion, it's a good engineering practice.


regarding the water inside the pipe for several months it could be a microbiological corrosion



Corrosion Prevention & Corrosion Control

RE: passivation of new piping

Why try to undertake 'damage control' for the construction contractor?  After all, they did leave unacceptable water in the piping so I wouldn't be feeling too sorry for them even if they are the usual 'South Oman mob'.  

Don't worry - until you went public with the problem, I doubt if anyone beyond Muscat had heard of it.  I can see that all is still 'normal' there!

Steve Jones
Materials & Corrosion Engineer

RE: passivation of new piping

Ahh Mr. Jones, if it had been the construction contractor who had left the water in the pipe, I would not be going to bat for them.  It was however our own commissioning team who left the water in the pipe.  I'm not trying to really protect anyone, but I didn't want to see any blame assigned incorrectly.  And from I understand, nothing has changed from "normal" in Muscat for quite some time, at least not in my two years on the project.
Strider 6, yes you are correct for the outside of the piping at the weld joints, however it is not so easy when dealing with long pipe runs to do the same internally.  Also, we determined the corrosion was not based on MIC, although that was one of the initial concerns.  Our metallurgist has also stated that we would have most likely seen the same corrosion activity if totally clean, potable water had been used.  The additional corrodents only sped up the process.

RE: passivation of new piping

For the long piping runs you could have retrojetted with an appropriate cleaning solution if you had to.  BJ would have come down from Dubai to do it (unless you are already 'batting' for BJ!!!)

The Contractor is probably used to being under scrutiny - they'll not suffer for it.

Steve Jones
Materials & Corrosion Engineer

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