THE EFFECT OF CORROSION ON THE DYNAMIC BEHAVIOUR OF AISI 4140, AISI 4340, AND AISI 5140 STEELS EXPOSED TO 3.5 wt.% NaCl ENVIRONMENT

Material loss due to corrosion can weaken the structural integrity of systems and potentially lead to failure if timely action is not taken. Such deterioration adversely affects the dynamic behavior of metals. This study deals with the post-corrosion changes in the dynamic behavior of AISI 4140, AISI 4340 and AISI 5140 metals after exposure to 3.5 wt.% NaCl for 1, 7, 15 and 30 days. Electrochemical impedance spectroscopy (EIS) and dynamic electrochemical impedance spectroscopy (Dynamic-EIS) were used to elucidate the corrosion mechanisms. Modal analysis and finite element method (FEM) were used to characterise dynamic behavior changes. In addition, scanning electron microscopy (SEM-EDS) was used to analyse changes in surface morphology after corrosion. The results show a decrease in the corrosion resistance of AISI 4140, AISI 4340 and AISI 5140 metals over time, although there is an improvement after 30 days. The electrochemical test results indicated that the metal with the highest corrosion resistance in a 3.5 wt.% NaCl environment was 4340, while the lowest was 5140. In particular, the natural frequency values showed a decreasing trend with increasing corrosion exposure time, accompanied by discernible changes in mode shapes.