What is the solution for pipeline corrosion? 2

[Carloshhead]

Hi there, I'm Carlo, and I'm working as a safety technician in a shipbuilding company. Our company mainly uses pipes for transferring gases and other chemicals used for manufacturing the parts of the ship. We mainly use steel pipes. Every month we inspect the lines to find out the faults. The previous day we examined and found that there is a starting of corrosion. Last year we had done a corrosion resistance coating, but I think it was not much effective. Now we are planning to approach a professional team for a detailed as well as advanced corrosion coating.

 

[Dhurjati Sen]

Good thinking on your part. You do require professional guidance.

DHURJATI SEN

 

[Carloshhead]

Yes,I think so Mr.DHURJATI SEN

 

[EdStainless]

When doing coatings the three most import parts are surface preparation, surface preparation, and surface preparation.
There are some very good coatings out there. Typically you will pressure wash, media blast, primer or base coat, and then top coat. this will be done under controlled temperature and humidity conditions. They should also be testing for bond strength and coverage.

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P.E. Metallurgy, consulting work welcomed

 

[SWComposites]

Why not use a non corroding pipe material?

 

[TugboatEng]

Leave it to the composite guy to suggest plastic...

Actually, I like the idea but I see some complications. "Gasses used in the construction of ships" sounds a lot like oxygen and fuel gas (probably propane or propylene with a chance of acetylene). Pressures are low, <100 psi for the oxygen and <30 for the fuel gas. CPVC might work quite well for the oxygen piping. The same may be true for the fuel gas but pushing combustibles through non-conductive pipe is outside of my rank. Copper is another good alternative. It's expensive to buy but cheap to run. Odorized fuel gasses may cause some corrosion if there is moisture in the line.

 

[Carloshhead]

Actually, the fact is that I have joined the company before 1 year. The pipes are already installed there. I think because of the high cost they used steel pipes.

 

[Carloshhead]

Mr. TugboarEng. What's the next step we can do now?

 

[TugboatEng]

I can't tell you what to do but you should start here if considering copper.

https://www.nfpa.org/codes-and-stan...ds/list-of-codes-and-standards/detail?code=51

I can tell you that copper will hold up very well in coastal environments. Without knowing the specifics of your application I feel that copper tubing based systems will be similar in initial purchase cost to coated steel but may cost less to install and will cost less over the life of the system.

 

[Carloshhead]

Okay, Mr. TugboatEng, let me discuss this matter with the companies higher authority. I think copper lines are better than steel lines. I think the immediate step we can do is to coat the pipelines with some corrosion resistance material. Will that be okay?

 

[Carloshhead]

At last, as a part of the enquiry, I found a group doing effective corrosion resistance processes. So we are planning to contact them and discuss this issue. I think this will be the immediate step we can put forward. If it's not too much trouble, share your perspectives, which will be very much helpful.

 

[1503-44]

You don't say if it is internal corrosion, or external corrosion, or both. your treatment options depend entirely on that information.

 

[Carloshhead]

Mr.1503-44, As per our inspection it's a starting of external corrosion. I don't know how much it affected internally. We are planning a detailed checkup with the corrosion resistance working team.

 

[CH. Lee]

best is to assess the damage, examine the fluids handled, perform a quick survey of the damaged sites and identify the possible corrosion mechanism and the cause of it.
I wouldn't jump to a conclusion to select a higher grade material without know the root cause of the issue. Changing a material and the material selection are another new study all together.


CH. Lee, PhD P.E
Lead Materials and Corrosion Engineer
Intecorr Consultancy

http://www.intecorr.com

twitter.com/intecorr

 

[gerhardl]

We are probably not discussing very large diameter pipelines here, but you mention that steel was selected because of price.

Why copper? Why notone of a multitude available of compositions of stainless steel? Often used in offshore constructions, readily commercial available and half the price or less tnan copper tubes?

 

[TugboatEng]

Why introduce the problems of crevice corrosion and SCC when thin walled copper will do just fine?

Underspecified stainless steel is the bain of my existence. That and split lock washers.

 

[gerhardl]

TugboatEng:

I agree in general. Depending on the fluid and operation specifications, and of course correct specification of the SS, it should normally not be an issue, but yes.

 

[TugboatEng]

But this is in a shipyard meaning grinders and sparks. Contamination of the surface is expected and will start corrosion.

 

[Carloshhead]

Mr.CH. Lee,
Thanks for your advice currently as an immediate step we are planned to coat the pipe with some corrosion resistance materials. I have discussed with the higher authority about the line issues. After examination, the situation is crucial surely we will replace the pipe with apt material.

 

[Carloshhead]

Mr. Gerhardt, The pipes were already installed before I joined the company. I think they used steel because of the coast. I think the safety team at that time suggested the steel.