The Influence of KCl and HCl on the High-Temperature Oxidation of a Fe-2.25Cr-1Mo Steel at 400 °C
Artikel i vetenskaplig tidskrift, 2019

The influence of alkali- and chlorine-containing compounds on the corrosion of superheater alloys has been studied extensively. The current paper instead investigates the corrosive effects of KCl and HCl under conditions relevant to waterwall conditions. A low-alloy (Fe-2.25Cr-1Mo) steel was exposed to KCl(s), 500 vppm HCl(g) and (KCl + HCl) in the presence of 5%O2 and 20% H2O at 400 °C. The results indicate that alloy chlorination by KCl occurs by an electrochemical process, involving cathodic formation of chemisorbed KOH on the scale surface and anodic formation of solid FeCl2 at the bottom of the scale. The process is accompanied by extensive cracking and delamination of the iron oxide scale, resulting in a complex, convoluted scale morphology. Adding 500 vppm HCl to the experimental environment (KCl + HCl) initially greatly accelerated the formation of FeCl2 at the scale/alloy interface. The accelerated alloy chlorination is attributed to HCl reacting with KOH at the scale surface, causing the cathodic process to be depolarized. A rapid slowing down of the rate of chlorination and corrosion in KCl + HCl environment was observed which was attributed to the electronically insulating nature of the FeCl2 layer which forms at the bottom of the scale, disconnecting the anodic and cathodic regions.

Corrosion mechanism

Chlorine-induced corrosion

Low-alloyed steel

KCl

Waterwalls

HCl

Författare

Erik Larsson

Chalmers, Kemi och kemiteknik, Energi och material, Oorganisk miljökemi

Jesper Liske

Chalmers, Kemi och kemiteknik, Energi och material, Oorganisk miljökemi

Amanda Persdotter

Chalmers, Kemi och kemiteknik, Energi och material, Oorganisk miljökemi

Torbjörn Jonsson

Chalmers, Kemi och kemiteknik, Energi och material, Oorganisk miljökemi

Jan-Erik Svensson

Chalmers, Kemi och kemiteknik, Energi och material, Oorganisk miljökemi

Lars-Gunnar Johansson

Chalmers, Kemi och kemiteknik, Energi och material, Oorganisk miljökemi

Oxidation of Metals

0030-770X (ISSN) 1573-4889 (eISSN)

Vol. In Press

Ämneskategorier

Annan materialteknik

Metallurgi och metalliska material

Korrosionsteknik

Infrastruktur

Chalmers materialanalyslaboratorium

DOI

10.1007/s11085-019-09943-9

Mer information

Senast uppdaterat

2019-12-03