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Investigation of Galvanic Corrosion between Graphite Gaskets and Stainless Steel Flanges
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
2015 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

At Forsmark, several cases of suspected galvanic corrosion have been detected and

believed to be caused by an inappropriate use of graphite gaskets in brackish water.

This report studies the likelihood of galvanic corrosion between the graphite gasket

and stainless steels and aims to be a reference when investigating galvanic corrosion in

the future. To evaluate galvanic corrosion, several electrochemical experiments were

studied, such as galvanic series, polarization curves, and galvanic current

measurements with a ZRA.

The electrochemical results showed that when immersing the stainless steel (254

SMO) and the graphite gasket (Novatec) into brackish water, there was a current

flowing between the electrodes. However, the current was very small, which could be

explained by the protection from a passive film on the stainless steel. The difference

in corrosion potential between the two materials was measured and compared to

results from polarization curves. It appeared that 254 SMO would be protected by a

passive film at the measured potential. Galvanic current measurements also indicated

the presence of a passive film under the investigated conditions.

The results indicate that galvanic corrosion itself should not have caused the

corrosion attacks at Forsmark. The found corrosion is more likely due to crevice

corrosion that was accelerated by the combination of a crevice, a welded flange

surface, chlorides in water and possibly a graphite gasket.

Place, publisher, year, edition, pages
2015.
Series
UPTEC Q, ISSN 1401-5773 ; 15007
Keyword [en]
Galvanic Corrosion
National Category
Corrosion Engineering
Identifiers
URN: urn:nbn:se:uu:diva-261888OAI: oai:DiVA.org:uu-261888DiVA: diva2:851449
Subject / course
Chemistry
Educational program
Master Programme in Materials Engineering
Supervisors
Examiners
Available from: 2015-09-07 Created: 2015-09-04 Last updated: 2015-09-07Bibliographically approved

Open Access in DiVA

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