Hot corrosion is the accelerated oxidation of material exposed to high temperatures induced by a molten salt. Electrochemical techniques are used to evaluate corrosion reactions under simulated conditions. Nowadays, corrosion monitoring on real time is not available for boiling materials; therefore, it is necessary to research about EIS and its application on monitoring equipment. An electrochemic al cell was built to evaluate corrosion rate of T -22 and AISI - 304H Steels in 80% V2O5 - 20% Na2SO4 electrolyte between 550oC and 800oC, by using Tafel and EIS. The results showed that for temperatures below 750oC, steels have a diffusional control in oxide film, while above 750oC the control is by diffusion in molten electrolyte.