Nowadays, there is an effort to increase the more widespread use of biofuels that are a renewable energy source in transportation and an alternative to conventional, petroleum-based fuels. These biofuels include alcohols such as biomethanol, bioethanol, and biobutanol that have a high octane number, but generally different physical and chemical properties than petroleum fuels. The different properties of alcohols may cause low material compatibility with carbon steel. Here, we used cyclic potentiodynamic polarization (CPP) to study the behavior of carbon steel in an environment of alcohols and alcohol-gasoline blends (AGBs). Using CPP, we proved that the corrosion of mild steel can be significantly influenced by alcohol properties, such as the chain length, pK a, and solubility of oxygen and water. In the environment of pure alcohols (not blended by gasoline), a very good passivation ability of steel was proven, especially for n-butanol. In AGBs, steel corrosion can also be influenced by the gasoline amount. When these pure alcohols or their gasoline blends are contaminated by water-containing chlorides and organic acids, the corrosion rate of carbon steel can increase by up to 4 orders of magnitude. In an anhydrous environment of alcohols, the CPP can give results with a very good informative value.
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