Corrosion Allowance

[Hishammat]

How can I determine a corrosion allowance value while selecting the material and making the material selection report without the use of ECE software? Is there a manual method?

 

[SJones]

https://www.eng-tips.com/search.cfm?pid=0&action=Search&q=CO2+corrosion+modelling

https://www.eng-tips.com/search.cfm?q=corrosion+allowance&action=search

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

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

 

[Hisham Al. Mohammad]

@SJones: How can I calculate it manually for new construction piping not in-services ?

 

[SJones]

As per ISO 21457:
"The corrosion evaluation should be based on a corrosion prediction model, or on relevant test or field
corrosion data agreed with the end user. General and localized corrosion of carbon steel takes place over
time, and the anticipated corrosion rate should be calculated for the operating conditions."

There are at least two CO2 corrosion prediction models that are free to download, one being NORSOK M-506. Once downloaded, review this document: IFE Guideline

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

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

 

[Hisham Al. Mohammad]

Thank you for your reply. There is no possibility of the CO2 corrosion due to the absence of water phase in the system on which I am currently working so, Shall I use ECE software to calculate it ? No any other ways to do the calculations ?

Hisham Mohammad
Material Engineer / Welding & Quality Engineer

 

[SJones]

ECE is a CO2 corrosion model akin to NORSOK M-506. If you believe that there will be no appreciable metal loss in operation, use the smallest corrosion allowance stipulated by the end user's piping specification and piping classes. Typically, this would be around the 1 mm value. Do you believe that there will be no metal loss, not even from the outside?

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

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

 

[jdonville]

For carbon steel buried in soil, here is one published conservative relation from FHWA NHI-00-044: Loss (from surface in contact with soil) = 0.08mm/y * (t^0.8), t is service life in years.

 

[Hisham Al. Mohammad]

@SJones: There will be a metal loss from the outside cause in Summer, the humidity exceeds 80% here in UAE and the temperature is high. Because of the absence of water phase, there is no CO2 corrosion, no H2S corrosion, no HIC & SSC corrosion. Only Atmospheric corrosion and CUI as well are there.

Hisham Mohammad
Material Engineer / Welding & Quality Engineer

 

[Hisham Al. Mohammad]

@jdonville: It is above ground not under ground.

Hisham Mohammad
Material Engineer / Welding & Quality Engineer

 

[SJones]

So, what is the minimum corrosion allowance stipulated by piping specifications?

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

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

 

[Hisham Al. Mohammad]

It is 3 mm so if, based on the calculations, I get 1.5 mm CA, I have to go for 3 mm as a minimum. But I have to make the calculations first to make sure it will not go beyond 3 mm.

Hisham Mohammad
Material Engineer / Welding & Quality Engineer

 

[SJones]

What is there to calculate if there is no internal corrosion expected? The external corrosion will be controlled by coating.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

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

 

[Hisham Al. Mohammad]

My question was a general one because there is a new project I have to calculate the corrosion rate as there is water phase and the internal corrosion is expected.

Thanks in advance for your replies and efforts Mr. Jones. Much Appreciated


Hisham Mohammad
Material Engineer / Welding & Quality Engineer