Significance of activation of test specimens for the determination of iso-corrosion curves of stainless steels
2005 (English)In: Corrosion, ISSN 0010-9312, Vol. 61, no 6, 602-608 p.Article in journal (Refereed) Published
The general corrosion resistance of a corrosion-resistant material, for instance, in an acid L's often illustrated in iso-corrosion curves; these curves can be used as a basis for material selection. Therefore, it is important that the information given in one diagram can be compared with diagrams from other sources. Information about the activation of the test specimens is not always given, which makes comparison difficult. Activation is often used to investigate whether the material has the ability to repassivate. In this paper two different forms of activation were used. either with a zinc rod or in boiling hydrochloric acid (HCl). For three superduplex stainless steels, UNS S32750, UNS S32760, and UNS S32520, with similar chemistry except for their copper and tungsten content, the influence of the activation method was studied using general corrosion rate tests in HCL The results were also compared with earlier results in sulfuric acid (H2SO4). No major influence of the alloying with copper and tungsten was found in the range where the materials are resistant, i.e., when they have low corrosion rates. However, in the reducing environments-HCl and H2SO4 at low concentrations-the activation of the test specimens narrowed this range. In contrast, in H2SO4 at high concentrations, which is a more oxidizing acid, it was indicated that activation did not appear to influence the corrosion rates. An activation procedure with boiling HCl seems to give higher corrosion rates than for specimens activated with zinc. However, the influence on the range seems to be minor and not as profound as without activation. Despite the fact that activation may significantly influence the corrosion rate, not all iso-corrosion diagrams indicate whether the experimental procedure includes activation. As a result, a material can be selected on misleading results.
Place, publisher, year, edition, pages
2005. Vol. 61, no 6, 602-608 p.
activation, general corrosion, hydrochloric acid, sulfuric acid, superduplex stainless steels
IdentifiersURN: urn:nbn:se:kth:diva-13434ISI: 000229825900010OAI: oai:DiVA.org:kth-13434DiVA: diva2:325333