Evaluering av alternative test metoder til ASTM G-48 for bestemmelse av kritisk grop og spaltkorrosjons temperatur for rustfrie stål og nikkel legeringer
Master thesis
Permanent lenke
http://hdl.handle.net/11250/241529Utgivelsesdato
2011Metadata
Vis full innførselSamlinger
Sammendrag
Pitting corrosion and crevice corrosion can be a problem for stainless steels and nickel-based alloys in seawater. In order to test materials for resistance against these types of corrosion, the standard ASTMG48 method is often used. However, this method is time consuming. In this work, it is evaluated if the standard ASTM G48 method can be replaced by one of the following test methods; the modified ASTM G48 method, the SINTEF method or the Zero Resistance Amperometry (ZRA) method. All these methods use continuous measurements to determine initiation of corrosion, which can give significant time savings compared to the standard method.
Existing experimental setups for the SINTEF method and the modified G48 method were used. The experimental setup for ZRA was built and tested, and was found to work satisfactorily.
Tests were performed with all four methods on 904L stainless steel (SS) and super duplex stainlesssteel (SDSS). The alternative methods gave a critical crevice temperature (CCT) for SS of 27 °C and for SDSS the CCT was found to be 56 °C. With the standard method, a CCT of 22 ºC was found for SSand 56 ºC for SDSS. The ZRA method was found to be the most promising, but due to issues with the current measurements for the SINTEF method more tests need to be performed before drawing a final conclusion.