The interest in terms of fuels who are based on ethanol, as a total or partial substitute for fossil fuels. In this research, three concentrations of water (0.5, 5 and 10%) by volume were evaluated, in ethanol-gasoline blends at 95% by volume of ethanol, using cyclic polarization curves (CPC) on API-5L X52. As a complementary technique, weight loss (WL) was monitored with exposures of 30, 60 and 90 days of immersion. The objective of this investigation is to determine the mechanism of corrosion and the measurement of the effect of the water related to the WL of steel, regardless to the ethanolic mixtures. The result obtained from the mass loss was increased when the water concentration was less than 5% by volume. The CPC showed that blends with low water content there is a tendency to the formation of corrosion by pitting, which was corroborated by scanning electron microscope (SEM).