Susceptibility to Pitting Corrosion of AerMet 100 and 4340 Alloys for Aeronautical Applications

In the aeronautics industry, high-strength steels such as AerMet 100 and 4340 are widely used in critical structural components that must withstand extreme operating environments. These materials possess high tensile strength, fracture toughness, and fatigue resistance. The aim of this investigation is to study the susceptibility to localized pitting corrosion of two aeronautics alloys, AerMet 100 and 4340, and their immersion in H2SO4, NaCl, and HCl solutions at room temperature, using electrochemical noise (EN) according to the ASTM ASTM-G199 standard. The EN signal was filtered by two different methods, and the polynomial method was employed to obtain Rn, LI, Kurtosis, Skewness, and the potential spectral density analysis (PSD). Results indicate that AerMet 100 exhibits lower corrosion rate—up to an order of magnitude lower than 4340. The resistance noise of 1599 Ω·cm2 in NaCl is higher. This same behavior is replicated when analyzing the noise impedance response (Zn). In conjunction with the analyses of PSD slope, it is reported that localized corrosion is the predominant mechanism in the evaluated environments.