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mthakur (Mechanical) (OP)
18 Jul 07 8:24
Dear all,
What is the basic difference between SS 316 and 316L interms of their resistance against corrosion in seawater service.
regards
NickE (Materials)
18 Jul 07 9:39
Is the assebly/component welded?

How hot does it get?

Seems to me that the L grade would have better consistancy part to part since the carbon content is better controlled. However much of the 316 I've seen is dual certed for 316/316L.
Helpful Member!  strider6 (Materials)
18 Jul 07 9:52
mthakur,

The Corrosion resistance of SS 316/316L in seawater, mostly pitting/crevice corrosion, is due to the presence of  Mo in concentration between 2-3%. The L means that the carbon is below 0.03%  and this make difference when you have to weld it. Lower concentration of C means no problems of sensitization and following intergranular corrosion.

hope this help

regards

Strider

http://www.corrosionist.com

EdStainless (Materials)
18 Jul 07 10:20
Well, neither really has much resistance in seawater.  If hte seawater is cold and the metal is clean then it might work for a while.  Any fouling of crevices will cause rapid pitting.

The real difference between the grades will be if there are any welds.  The welds in the straight grade material will have heat affected zones with some grain boundary carbide precipitation and they will be more likely to suffer intergranular corrosion.

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection
http://www.trent-tube.com/contact/Tech_Assist.cfm

0707 (Petroleum)
19 Jul 07 10:03

both are not good for seawater service, maybe SS 316L has a little bit more resistance...

Regards

Luis Marques
strider6 (Materials)
19 Jul 07 13:36
0707

I don't think that it's correct to say that a 316L is no good for a seawater service.
I agrre that under certain condition is not the right selection,stagnant conditions, temperature above a certain limit, but under other condition it could be a good choice.
The final selection of a material is not simply is good or is not good, but it will make the work i'm asking for or not, and a lot of parameters have to be considered: criticality of the service, cost, possibility to inspect...
I think this is the correct approach of a corrosion engineer  when selecting a material.

regards

Strider

http://www.corrosionist.com

0707 (Petroleum)
19 Jul 07 14:30
strider6


I was answering to a generalise question, but I keep on thinking that the referred materials are not the adequate ones for seawater services.

Please go to

http://www.swcc.gov.sa/files%5Cassets%5CResearch%5CTechnical%20Papers%5CCorrosion/Electrochemical%20Studies%20on%20the%20Corrosion%20Behavior1of%20Convent.pdf


Cheers

Luismarques
strider6 (Materials)
20 Jul 07 5:59
0707

I agree with you that as a general rule  316L could not be the perfect choice, but for certain components, pumps impeller for example, SS 316 can be used.
Seawater service includes so many equipment, components and so on that is not always possible to generalize.
This is my opinion.

regards

Strider

http://www.corrosionist.com

EdStainless (Materials)
20 Jul 07 8:49
316 works in seawater pumps when the cases provide galvanic protection.
Even boat rails made from 316 need to be washed and cleaned to prevent pitting.

= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection
http://www.trent-tube.com/contact/Tech_Assist.cfm

mthakur (Mechanical) (OP)
21 Jul 07 23:53
Dear All,
Thankf ro your feed back, its is clear that low carbon help in getting better protection beacuse of sensitization issues if exposed to elvetated temperature. My question was if there no such issues with carbide precipitation, will there any preference of using 316L over 316?

regards
strider6 (Materials)
22 Jul 07 6:07
No, if u don't have to weld it, is the same thing.

regards
Strider

http://www.corrosionist.com

arunmrao (Materials)
22 Jul 07 6:39
In reality the distinction between 316/316L is not going to be distict,as often one would  end up buying dual certified 316. Even 316 grades quite often contain 0.03% C thanks to AOD and other refining techniques.

" All that is necessary for triumph of evil is that good men do nothing".
Edmund Burke

mcguire (Materials)
22 Jul 07 18:20
There is a small beneficial effect on both yield strength (higher) and pitting resistance from higher carbon levels as long as it's quenched into solid solution.

Michael McGuire
http://stainlesssteelforengineers.blogspot.com/

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