Corrosion by naphthenic acids and sulfur compounds is a major concern for crude oil refineries. Corrosion rates in both field and laboratory studies demonstrate corrosion product scales are partially protective in ways that are difficult to predict. In prior research, a protective oxygen-containing scale in the corrosion by naphthenic acids under stagnant conditions was found. Current research expands the study on the formation of protective scales by investigating the effect of temperature under replenishing conditions. It was found that the presence of both acids and sulfur compounds was necessary to form a protective scale under replenishing conditions. The scale formed at higher temperature was more protective than that formed at lower temperature. It was postulated that the corrosion in the presence of both naphthenic acids and sulfur compounds proceeded by the solid-state diffusion of ferrous ions through the inner scale adjacent to the steel surface.