DEGRADATION OF MILD STEEL IN ETHANOL BURNING ENVIRONMENT: OXIDATION KINETICS AND MICROSTRUCTURAL ASPECT

Abstract

The isothermal oxidation of an AISI 1005 steel (mild steel) in water vapour and CO2 mixtures
containing environments resulted from ethanol combustion had been investigated for exposure times ranging
from 1 hour to 49 hours at elevated temperatures (700 °C, 750 °C and 800 °C). The steel was also oxidized in
dry air for comparison. In water vapour and CO2 environments, mild steel underwent a significant degradation
in term of the oxidation kinetics compared with those of steel oxidized in dry air environment. This finding is
supported by a lower activation energy for steel oxidized in ethanol combustion products (199 kJ/mol) than
that of for steel oxidized in dry air (224 kJ/mol). In addition, the breakaway oxidation was found for the steel
subjected to ethanol combustion products at 800 °C. The carbon deposited in the magnetite layer was believed
to lead the breakaway oxidation after an exposure time for 4 hours. A typical iron oxide growing on steel
oxidized in ethanol combustion product is a pyramidal grain structures with compact scale but in dry air
environment the iron rich oxide growing on the steel surface is a wrinkle characteristic displaying hollow
structures at 700 °C and rough-grained oxide structures at 750–800 °C.