This paper examines the causes and extent of corros ion that occurs on the outside of the heat exchangers for oil automatic tr ansmission, made from stainless steel plates 304 or 410. It was determine d the corrosion rate of specimens using the technique of electrochemical li near polarization resistance, with a system of three electrodes and three media e xposure (H2O solution of OY and automotive antifreeze) 25 and 60 ° C. It was no ted that the 304 stainless steel with copper contaminated a kinetic corrosion than the steel that is not polluted and that 410 steel is not contaminated by copper.