It has been known that material strength used in corrosive environment will be lowered compared with structural materials used in air due to the effect of corrosion fatigue. However, there are few research data concerning fatigue tests under petrol environment assuming actual usage. In this study, fatigue tests on a type of 440C stainless steel, which has been used as a part of the automobile fuel injection system, under air and petrol environment were conducted by means of a small sized specimen and a small sized fatigue testing machine performable in corrosion and flammable liquid. The testing machine can be also used for fatigue tests under push-pull loading at high frequency region. In addition, the fracture surface was observed by SEM and EDS to confirm the difference of fracture morphology in air and corrosive environment. Additional fatigue tests were also conducted in order to investigate the mechanism of corrosion fatigue. Fatigue lives in air were on the same level as those in regular petrol while fatigue lives in deteriorated petrol focusing on corrosion were dramatically decreased due to the difference of fracture origin.
