Effect of the composition on the corrosion behavior of austenitic and martensitic stainless steels

The aim of this work is to study the electrochemical behavior of a series of stainless steels in NaCl solution (10000 ppm Cl-) at room temperature. Considering the differences in structures (austenitic and martensitic) and the composition of alloys, a relationship between their electrochemical behavior and PREN (Pitting resistance equivalent number) was sought. Stainless steels used were: F6NM, 17-4PH, 416 and 304. Measures of open circuit potential in function of time, cyclic potentiodynamic polarization curves, determining the polarization resistance by ASTM G59 (Tafel) and Electrochemical Impedance Spectroscopy (EIE) were carried out. These studies were complemented by observations of the specimens under optical microscopy. The analysis of the results, obtained from the electrochemical tests, allowed to find a relationship between the corrosion behavior, its composition and its PREN, independently of the microstructure that having each.