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- 2015 (3)
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- Beitrag zu einem Tagungsband (3) (entfernen)
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- Stainless steel (3) (entfernen)
Pitting corrosion is one of the most common mechanisms of local passivity breakdown on stainless steels. Electrochemical methods have preferentially been applied for the evaluation of pitting corrosion resistance of stainless steels in laboratory. Nevertheless, some of them are not reliable enough and in general the application of electrochemical methods in the field becomes difficult because of a required deep understanding of corrosion phenomena and measurement technology. A new approach for the evaluation of the pitting corrosion susceptibility of stainless Steel surfaces in the laboratory as well as in the field is frequently demanded by representatives of the metalworking industry. Therefore, the KorroPad-test was invented and patented as part of a research project at the BAM Federal Institute for Materials Research and Testing in Germany.
Contents of deformation-induced martensite in the lattice structure of austenitic stainless steels lead to an either beneficial or detrimental change of mechanical and magnetic properties depending on the prospective application. Whereas these changes are well-known and investigated widely the influence of deformation-induced martensite on the corrosion behaviour is frequently an issue of scientific discussions. There are opposing opinions that depend on the type of corrosion mechanism being investigated for example regarding pitting corrosion resistance in Chloride containing media. In it is stated that pitting resistance is not influenced by deformationinduced martensite while in it is discussed that more pitting occurs on martensitic structure. The same conflictive opinions appear regarding active dissolution in acidic media or intergranular corrosion. In addition, when having deeper insight into literature it can be concluded that even the type of test method, i. e. dynamic or static testing, has a big influence on the obtained results concerning the influence of martensite in austenitic stainless steels.
Mit Hilfe des KorroPad-Prüfverfahrens konnten verschiedene umgebungs- sowie prozessbedingte Einflüsse in Parameterstudien gezielt untersucht werden. So konnte der negative Einfluss von korundbasierten Schleifmitteln auf die Passivschichtausbildung nachgewiesen werden. Weiterhin konnte mittels KorroPad die Wirksamkeit verschiedener Oberflächenbearbeitungsverfahren bei der Schweißnahtnachbearbeitung untersucht und daraus Erkenntnisse für die Prozessoptimierung gewonnen werden. In den hier gezeigten Untersuchungen hat sich das KorroPad-Prüfverfahren für die Beschreibung der Passivschichtstabilität als hervorragend geeignet erwiesen.