Stress corrosion cracking of microalloyed pipeline steel in biofuels E-10 and E-85

This paper evaluates the stress corrosion cracking (SCC) effect in gasohol E-10 and E-85 of X-70 experimental Ni-microalloyed steel, with different aging treatments (4–12?h at 600°C). The tension tests show that for all treatment periods, the samples tensile strength and elongation increase, with the largest increment exhibited by the samples undergoing 4 and 6?h of aging treatment. Microstructural analysis showed that the microstructure remains unchanged, the increase in tensile strength in the steel is directly related to the precipitation kinetics. The slow strain rate test (SSRT) shows that the steel under all conditions presents no susceptibility to SCC, thus reducing the area ranging from 83% to 90%, with predominantly ductile fractures. The results of the polarisation tests showed no signs of pitting corrosion, as well as a low corrosion rate for both media under study.