EFFECT OF HEAT TREATMENT ON CORROSION RESISTANCE OF Al-Ni-Mn EUTECTIC ALLOY IN 3.5% NaCl SOLUTION

Abstract

In this study, the effects of solution heat treatment (SHT) on how the Al-Ni-Mn eutectic alloy reacts to corrosion were looked into. The composition of the Al-Ni-Mn eutectic alloy was chosen as Al–5.3%Ni–1.3%Mn (wt). In solution heat treatment, firstly, the samples were kept at 570oC and 600oC for 2 hours and quenched with water at room temperature. Then, artificial aging was carried out by keeping 0-2-4 and 8 hours at 180oC. The corrosion behavior of the alloy was investigated by immersion tests in a 3.5% NaCl solution and electrochemical methods such as Tafel polarization curves and Electrochemical Impedance Spectroscopy (EIS). According to the immersion test results, the heat treatment applied at 600oC took the alloy to the more noble side and further increased its corrosion resistance. The α-Al matrix phase in the Al-Ni-Mn alloy system preferentially dissolves in untreated and heat-treated samples, and SEM images reveal the presence of corrosion pits. The corrosion performance of the heat-treated sample at 570oC is the highest. Heat treatment reduced the corrosion current density, indicating a lower corrosion rate and higher corrosion resistance. Also, the open circuit potential of the Tafel polarization curves of heat-treated and unheat-treated samples at 570oC and 600oC was found to be -685 mV, -693 mV and -761 mV, respectively. Similarly, the corrosion resistance of heat-treated and untreated samples at 570oC and 600oC was found to be 58 kΩ, 433 kΩ and 408 kΩ, respectively.