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pipeline seawater corrosion

pipeline seawater corrosion

RE: pipeline seawater corrosion

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?

RE: pipeline seawater corrosion

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


RE: pipeline seawater corrosion

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

Sr. Process Engineer

RE: pipeline seawater corrosion

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

RE: pipeline seawater corrosion

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.


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

You're welcome ....

Sr. Process Engineer

RE: pipeline seawater corrosion

Interzone 954 recommends a primer.

RE: pipeline seawater corrosion

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

RE: pipeline seawater corrosion

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.


RE: pipeline seawater corrosion

No cathodic protection system present?

RE: pipeline seawater corrosion

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

RE: pipeline seawater corrosion

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

RE: pipeline seawater corrosion

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 ?

RE: pipeline seawater corrosion

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

RE: pipeline seawater corrosion

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.

RE: pipeline seawater corrosion

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.

RE: pipeline seawater corrosion

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

RE: pipeline seawater corrosion

Quote (OTHMANE001)

Stevenal, what do you mean by that?

You posted a diagram of a two part piping system; one part protected with an impressed current cathodic system, and the second part electrically isolated from the first and un-protected and rusted through. It would appear the system is working where it exists. Can the system be extended? Perhaps the original designer considered the second part replaceable.
I live near a fishing port, and can state that steel hulled boats nearly always use coatings along with cathodic protection.
The local aquarium piping systems are PVC, but I don't think they have anything of the diameter you show.

RE: pipeline seawater corrosion

I've had a lot of success with Unobtanium.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

RE: pipeline seawater corrosion

W B Holtsbaum, "Internal Stray Current Interference From An External Current Source," Materials Performance, August 2007, pp 40 - 42

An insulating flange, or monolithic isolating joint, is nigh on useless with such a conductive fluid and leads to lovely holes on the unprotected side. Usually, time to perforation is measured in months rather than years, but something worth looking at.

Steve Jones
Corrosion Management Consultant


All answers are personal opinions only and are in no way connected with any employer.

RE: pipeline seawater corrosion

I agree with the sage advice of Ironic Metallurgist....

Unobtainium is highly corrosion resistant in seawater (if you can get it) but very expensive

Short of that, go with titanium, it has a superb record in chlorides ....

Sr. Process Engineer

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