SS 304 piping in Coastal area 3

[powerbouy]

I have a situation where I have to select a material for Pipes which will be installed in a coastal area in a proximity of 1kms from sea, Our current selection is SS304 but I understand that it will not suffice and will get corrode easily. I am planing to use 316ti but any suggestions from you all will be really helpful, the operating temperatures will not exceed 100⁰C.

 

[kingnero]

Medium? Pressure? Perhaps anything else that might help us help you?

 

[powerbouy]

thanks for your quick response

medium is
1. lube oil @ 16barg & 100⁰C
2. water supply @ 10barg & 100⁰C
3.control air @ 13barg & 70⁰C

piping is for powerplant project

 

[EdStainless]

A less costly and higher performance option to 316 would be a duplex stainless steel.
There are a number of lean duplex grades (2102,2201,2202) that are strong (use thinner walls) and more corrosion resistant then 316. In many cases they even cost less.
IF you want a really step up in corrosion look at 2205.

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P.E. Metallurgy, Plymouth Tube

 

[weldstan]

304 is not your best choice. See Ed.

 

[powerbouy]

Thanks for your response Ed,I will definitely look into 2205.
but I have one more query, is SCC (Stress corrosion and cracking) the main culprit in costal areas due to salty air? and if the answer is yes, can we also coat the 304 with some epoxy coating?

 

[SJones]

Chloride stress corrosion cracking (ClSCC) will be the prime degradation mechanism. Introducing organic coating as a barrier against the threat of ClSCC brings up some further issues:

1.
It's not easy to apply coatings with good quality to small diameter pipe ≤DN 50

2.
The coating barrier will have to be maintained during the facility lifetime creating an operating expenditure for maintenance

3.
Cracking of the 304 could still occur in regions where the coating is degraded or damaged.

4.
Degraded coating can itself create the conditions to initiate crevice corrosion damage

If leaks are not tolerable, it will probably be a more resistant material that gets you to ALARP.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

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

 

[EdStainless]

At 100C CSCC is certainly possible.
Organic chloro-amines are far more aggressive than straight salts.
You will only get SCC if there is active corrosion, but there is no warning.
Coatings can help, but they take constant monitoring and maintenance. Not usually a workable option.
This is another reason to consider a duplex, they have useful resistance to CSCC.

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P.E. Metallurgy, Plymouth Tube

 

[powerbouy]

Thanks for your detailed reply, i guess this solves my query. this was my first thread at eng-tips and i must say its a great thing to communicate with experts worldwide, thanks once again