pipeline seawater corrosion

[OTHMANE001]

Hello,
I share with you an illustrative photo of the prematurely degradation of a seawater pipe DN 1750mm, Pression 6 bars, a few months ago, we suspect that this is microbiologique corrosion
Please share with us the problem causes of these mode of degradations

 

[mk3223]

It looks like a combinations of the corrosion and pin holes corrosion from inside out.
Was the pipe in the intermittent operation condition?
How does the corroded pipe internal look like?

 

[0707]

to share with you, we need more information about your story, the foto is no enough clear.

lm

 

[MJCronin]

Like many posts we get on this forum, there is hardly any information presented....

My questions are:

1) What material is the piping system ? .... Is it carbon steel ?
2) Where are you located ?....or.... Exactly which seawater is in the pipe ?
3) What is the flowrate ? .... Has the system been subject to long periods of shutdown ?
4) You say "prematurely degradation"... How long has the system been running ?
5) Cut the pipe at the point of failure and examine the insides... take pictures and post them

MJCronin
Sr. Process Engineer

 

[OTHMANE001]

Thanks mk3223 for your answers,
please find attached the picture of internal pipe corroded .

More information is below :

Material : S235 CS,
condition of function : 24h/24/h 7j/7j ...
Flowrate 30000 mcph
The system has been running for 10 years approx.

Nacl 40g/l
Matière organique 10,8mg/l
Calcium 497mg/l
Fluor 3,9mg/l
Sulfates 2,85g/l
Phosphate 1,74mg/l
PH 7,5 à 8,1

 

[MJCronin]

Othman ....

So you got ten years service in salt water using carbon steel pipe ?

... and your corroded piping material (S235) is a Structural Steel grade, not a steel grade made specifically for a piping system or found to be suitable under any of the EN or USA/ASME piping codes... Is that correct ?

... and your Structural steel grade pipe was subject to 6 bar internal pressure ?

I believe that you have normal and customary corrosion and rust as is always found with carbon steel in salt water conditions.

Investigation of a determination of MIC in piping systems is best left to a paid expert. There are guidelines available on the internet. MIC is a problem most often found in stagnant fresh water piping systems.

https://www.onepetro.org/conference-paper/NACE-07515

Consider replacement of your system using an internally and externally coated carbon steel piping.

You're welcome ....

MJCronin
Sr. Process Engineer

 

[OTHMANE001]

Thanks MJCronin for yours answers;
there is a mistake i correct : Pipe material is E-36 internal coated interzone 954 . ( see attached picture) external coated bitum

 

[TugboatEng]

Interzone 954 recommends a primer.

 

[EdStainless]

10 years of service with simple coated steel is pretty good.
Look into better coatings. A number of the photos show obvious local coating failure.
Is there any filtration on the seawater? Any biocide?
Usually for raw seawater people are looking at three layer coating systems, primer, seal coat, protective top layer often containing additives to suppress biofouling.
You might consider cement lined pipe for this application also.

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P.E. Metallurgy

 

[0707]

When the coating of your pipe fails you get this pin holes of corrosion. Increase your piping material or install a new coating based on epoxy cement lining or something alike.

luis

 

[stevenal]

No cathodic protection system present?

 

[OTHMANE001]

Hello,
Thanks for all your anwsers, is very helpful.
There was a biocid injection in time, but now there's no.
Please find attached annother picture of internal seawater pipe.

 

[OTHMANE001]

Stevenal,
There is no cathodic protection.
Please find attached an illustrative schema for pipe segment

 

[EdStainless]

You can tell whoever thought that they were saving money by not using biocide that they are responsible for the early failure of the pipe.
Even very good coatings will fail faster when they are fouled.
Biofouling is very tough on surfaces, both the live organisms and the decomposition of them when they die.

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P.E. Metallurgy

 

[stevenal]

That picture sure makes the point, doesn't it?

 

[OTHMANE001]

Stevenal, what do you mean by that?

in yours opinions, which is the most recommended material for the application of high flow and high pressure seawater, especially with the high presence of biofouling. ?
did you think that CS with copper based antifouling paint it's a solution for long-term ? or FRP with Derakane 411 an be also good ?

 

[TugboatEng]

Titanium. If you want a pipe you can simply install with minimum design and do no maintenance then titanium is your answer.

 

[LittleInch]

Warm aerated seawater is incredibly corrosive to steel - mm per year if left without adequate coating or cathodic protection and more so when flowing water or when marine growth is permitted.

So you have a few choices

Make it out of Carbon steel, coat internally and externally with a coating designed to handle seawater, dose it with biocide on a regular basis or you can get some copper anodes which slowly dissolve ( providing you're not returning the water back to the sea), add some cathodic protection and reckon on a limited life span. Internal concrete is pretty good as well, but any coating risks breakdown and rapid corrosion when the base material is so susceptible to corrosion.

Or use an inert material.

Metals you're looking at titanium or maybe Super Duplex steels - great but cost a fortune.
Not sure about Akuminium but worth a look - can corrode very fast if you get galvanic corrosion going on.
"Normal" Stainless Steel tends to pit over time and fail.

Or use an inert material such as Poly Ethylene, Glass reinforced epoxy, or similar. Concrete is pretty good but might not like 6 bar. ditto ductile Iron.
Each has its pluses and minus points.

You could sleeve this pipe with PE if you can scrape most of the marine stuff off it.


Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[LittleInch]

I'll echo a few other here - to get 10 years out of this with what looks like virtually no maintenance or biocide / inspection isn't "premature failure" it's actually quite remarkable life.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[EdStainless]

What ever you use you must use a biocide and conduct periodic (every couple of years) cleaning.
If you can handle the pressure FRP might be the best solution. But it needs to be protected from sunshine (either buried or painted) and that needs to be maintained. And since it is softer than metal or concrete you need more care when you clean it.
Cleaning the ID of the existing line, welding patched in the worst places, and slipping a PE liner into it may be the lowest cost way to go.

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P.E. Metallurgy