Open Circuit potential for metals

[Mrinet]

Anyone know where I could get open circuit potential values for materials like 254SMO, SAF2507, SAF2205, coated Carbon steel agaist Calomel or AG/Agcl electrodes?

 

[CoryPad]

Politely asking Outokumpu:

http://www.outokumpu.com/

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[EdStainless]

All high performance stainless grades are grouped closely. There is not much difference because the passive film is very similar in composition. The entire range from 317 (or 2205), up through the high alloy grades(super-austenitic and super-duplex) is less than 0.2V.

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Plymouth Tube

 

[SJones]

In what environment?

Steve Jones
Materials & Corrosion Engineer

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

 

[Mrinet]

Thanks for repsonses. We noticed severe corrosion (within one year) to the duplex pump which was galvanically coupled with 254SMO, medium was sea water. Since these high performance SS have very close potential difference, corrosion rate must be longer...Any idea?

Steve,
In sea water.

 

[strider6]

In this article you can find Cyclic polarization curves of high alloy stainless steels in seawater (Fig 26).

CREVICE CORROSION OF HIGH ALLOY STAINLESS STEELS IN SWRO PILOT PLANT

http://www.swcc.gov.sa/files\assets...F HIGH ALLOY STAINLESS STEELS IN SWRO PIL.pdf

are you sure that the corrosion mechanisms is a galvanic corrosion? Maybe i'm wrong but in my opinion there should be no problem in coupling these materials.

S.

Corrosion Prevention & Corrosion Control

 

[TVP]

I doubt that this is galvanic corrosion. Is the temperature elevated above ambient? What is the possibility of surface contamination? Crevice corrosion?

 

[EdStainless]

I am also guessing that if your duplex was 2205 it simply failed by pitting/crevice corrosion. You really need a super-austenitic or super-duplex in order to stand up in seawater.

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Plymouth Tube

 

[Mrinet]

Thanks for all the responses.

TVP:- Temperature is not above ambient.. we operate in NS (Danish) so below 18C.

Plymouth Tube/TVP:- I observed some crevice but also hypochlorite being circulated in regular basis.

Mrinet

 

[strider6]

if it's a 2205 then is not the correct materials for a seawater service. You've to use at least a 2507 (pren >40). the corrosion could be a crevice corrosion or pitting.

Corrosion of Duplex Stainless Steels in Seawater

http://www.outokumpu.com/applications/upload/acom_10292653.pdf?docid=681

S

Corrosion Prevention & Corrosion Control