The effects of KCl, NaCl and K2CO3 on the high-temperature oxidation onset of Sanicro 28 steel

A1 Journal article (refereed)


Internal Authors/Editors


Publication Details

List of Authors: Jingxin Sui, Juho Lehmusto, Mikael Bergelin, Mikko Hupa
Publisher: Springer US
Publication year: 2016
Journal: Oxidation of Metals
Journal acronym: OXID MET
Volume number: 85
Issue number: 5
Start page: 565
End page: 598
eISSN: 1573-4889


Abstract

The present study investigates the early stages in the oxidation process of Sanicro 28 (Fe31Cr27Ni) stainless steel when exposed to an alkali salt (KCl, NaCl or K2CO3) for 2 h at 450 and 535 °C. After the exposure, the oxidized samples were analyzed with a combinatory method (CA, XPS and SEM–EDX). It was found that all three salts were corrosive, and the overall oxidation reaction rate was much higher at 535 °C than at 450 °C. There were clear differences in terms of the impact of cations (Na+, K+) and anions (Cl−, CO32−) on the initial corrosion process at both temperatures. When focusing on the cations, the presence of potassium ions resulted in a higher rate of chromate formation than in the presence of sodium ions. When studying the effect of anions, the oxidation of iron and chromium occurred at higher rates in the presence of both chloride salts than in the presence of the carbonate salt, and chloride salts seemed to possess higher diffusion rate in the gas phase and along the surface than carbonate salts. Moreover, at the higher temperature of 535 °C, the formed chromate reacted further to chromium oxide, and an ongoing oxidation process of iron and chromium was identified with a significantly higher reaction rate than at 450 °C.


Keywords

Alkali salts, Corrosion onset, High temperature oxidation, Sanicro 28

Last updated on 2019-18-06 at 06:28