Electrochemical Study of 17-4 and 17-7 PH Stainless Steels Used in the Aeronautical Industry

In the aeronautical industry, precipitation hardenable (PH) stainless steels are accessories used in aircraft, turbine blades, and other parts. These alloys are alloys of iron, chromium, and nickel, characterized by mechanical strength obtained through age hardening by heat treatment. The addition of elements such as Al, Ti, Mo, and Cu lead to the appearance of intermetallic compounds. In this work, we performed electrochemical corrosion testing of 17-4 PH and 17-7 PH stainless steels with cyclic polarization and linear polarization resistance tests, showing the susceptibly of these stainless steels to pitting and intergranular corrosion. These tests were carried out in an electrochemical cell with a saturated calomel reference electrode at room temperature. The solutions were hydrochloric acid (HCl), sodium chloride (NaCl), and neutral (H₂O) environments. The results in the neutral environment showed that 17-4 PH had more pitting than 17-7 PH; they had similar behavior in a salty environment. 17-4 PH and 17-7 PH generally presented corrosion in an acid environment. The susceptibility to corrosion of stainless steel types 17-4 PH and 17-7 PH was demonstrated; however, the environment is a vital factor in the behavior of this steel.