STEEL GRIPS online - Corrosion of 12 % ferritic steel and weld joints in H2SO4 environments

STEEL GRIPS online
ISSN 1866-8453

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Feb 6, 2012

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Gadadhar Sahoo, Kilaru Ravi, and Srikanti Srikanth:
Corrosion of 12 % ferritic steel and weld joints in H2SO4 environments

Flue gas, corrosion, ferritic stainless steel, sensitization, EPR test

Plain carbon steel structures, exposed to flue gases, are often severely corroded. Sulphur dioxide (SO2) and sulphur trioxide (SO3) in the flue gas form sulphorus acid (H2SO3) and sulphuric acid (H2SO4), respectively, on contact with water vapour. In this study, a 12 % chromium (Cr) ferritic stainless steel was explored to replace plain carbon steel in corrosion prone SOx containing flue gas environment. The corrosion behaviour of 12 % Cr ferritic stainless steel was assessed and compared with that of AISI 430 and carbon steel by conducting the potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) scan in 0.5 N H2SO4. While plain carbon steel corroded actively, the passive current density of 12 % Cr ferritic stainless steel was in the similar range to that of AISI 430 stainless steel. The double loop electrochemical potentiodynamic reactivation (DLEPR) test was carried out for the heat-affected zone (HAZ) of the weld joint of 12 % ferritic stainless steel in 0.5M H2SO4 + 0.01M KSCN solution and sensitization of HAZ was not ascribed.