TY - GEN
T1 - The effect of HCl and SO2 on gas phase corrosion of boiler steels
AU - Tuurna, Satu
AU - Szymon, Sroda
AU - Heikinheimo, Liisa
PY - 2004
Y1 - 2004
N2 - The high temperature corrosion kinetics and mechanism of
different steel types, typically used in boiler
applications, were investigated. Materials were exposed
in simulated moist air atmosphere (8%O2 + 15%H2O) with
200 ppm SO2 and 2000 ppm HCl addition at temperatures of
500 and 600°C. The measured mass mass change for
different exposure times up to 360 h shows that in the
conditions used the oxidation rate of studied samples
obeys parabolic rate law. Corrosion products, growing on
tested materials, were analysed by SEM/EDS and XRD
techniques. The obtained results indicated a significant
influence of gas composition and temperature on the
morphology and growth rate of the corrosion product. The
presence of chlorine in simulated combustion atmosphere
accelerates the oxidation process. In general, the
oxidation layers formed in moist air with HCl addition
are more prone to spallation, exhibits large porosity and
several cracks. The observed morphology and composition
of the oxide scales suggest that in this case the
corrosion mechanism could be described as active
oxidation process. Active oxidation assumes that the
oxide scale contains physical defects through which the
gas phase chlorine and oxygen can diffuse to reach the
scale/metal interface. Then the iron is chlorinated, and
volatile or condensed FeCl2 can form. In contrast, in the
most of the studied cases the presence of sulphur seems
to slow down the corrosion rate. The growing scales are
more dense and adherent to the base metal. The sulphides,
which were formed mainly at metal/scale interface, may
play the significant role in ion transport through the
scale
AB - The high temperature corrosion kinetics and mechanism of
different steel types, typically used in boiler
applications, were investigated. Materials were exposed
in simulated moist air atmosphere (8%O2 + 15%H2O) with
200 ppm SO2 and 2000 ppm HCl addition at temperatures of
500 and 600°C. The measured mass mass change for
different exposure times up to 360 h shows that in the
conditions used the oxidation rate of studied samples
obeys parabolic rate law. Corrosion products, growing on
tested materials, were analysed by SEM/EDS and XRD
techniques. The obtained results indicated a significant
influence of gas composition and temperature on the
morphology and growth rate of the corrosion product. The
presence of chlorine in simulated combustion atmosphere
accelerates the oxidation process. In general, the
oxidation layers formed in moist air with HCl addition
are more prone to spallation, exhibits large porosity and
several cracks. The observed morphology and composition
of the oxide scales suggest that in this case the
corrosion mechanism could be described as active
oxidation process. Active oxidation assumes that the
oxide scale contains physical defects through which the
gas phase chlorine and oxygen can diffuse to reach the
scale/metal interface. Then the iron is chlorinated, and
volatile or condensed FeCl2 can form. In contrast, in the
most of the studied cases the presence of sulphur seems
to slow down the corrosion rate. The growing scales are
more dense and adherent to the base metal. The sulphides,
which were formed mainly at metal/scale interface, may
play the significant role in ion transport through the
scale
M3 - Conference article in proceedings
SN - 951-38-6291-7
T3 - VTT Symposium
SP - 233
EP - 243
BT - BALTICA VI - Life management and maintenance for power plants. Vol. 1
PB - VTT Technical Research Centre of Finland
CY - Espoo
T2 - BALTICA VI - Life Management and Maintenance for Power Plants
Y2 - 8 June 2004 through 10 June 2004
ER -