The protective effectiveness of oil compositions in the presence of sulfur dioxide was studied. The moisture permeability of oil films and the corrosion rate of steels both protected and unprotected by oil films increase with increasing relative humidity and initial sulfur dioxide concentration in the atmosphere. The contribution of individual components to the protective effect of a film of synthetic Mobil-1 oil inhibited by the additive Emulgin in the presence of sulfur dioxide is considered. The total protective effectiveness of the system can reach 93-96% after one day in 0.5 M sodium chloride solution containing sulfur dioxide and the products of its interaction with water. The slowdown of steel corrosion under a layer of inhibited and non-inhibited oil film is mainly due to retardation of the cathodic process with slight inhibition of the anodic reaction.