Stress corrosion cracking of carbon steel in ethanol-gasoline blends

Stress corrosion cracking of carbon steel in aerated ethanol-gasoline blend was studied using notched slow strain rate testing. Characterization of the fracture surface was made using SEM and SEM-EDS. Intergranular stress corrosion cracking (SCC) was produced in ethanol-gasoline blend with 15.5 wt% ethanol that was produced by evaporation of light C4 and C5 fractions from the ethanol-gasoline blend with 10.4 wt% of ethanol. Chloride concentration of 2 mg/L was found to cause transition from intergranular SCC to fully transgranular SCC in ethanol-gasoline blend with 85 wt% of ethanol. Transgranular SCC was found to initiate mainly at the pearlite phase and intergranular SCC initiated equally on the pearlite and ferrite phases. Chloride caused localized crystallographic pitting on the transgranular SCC fracture surfaces near the lamellar cementite left on the steel surface due to selective dissolution of ferrite from pearlite.