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Influence of annealing on the electrochemical behavior of finemet amorphous and nanocrystalline alloy

Shivaee, Hossein Asghari, Golikand, Ahmad Nozad, Hosseini, Hamid Reza Madaah, Asgari, Mehdi
Journal of materials science 2010 v.45 no.2 pp. 546-551
X-ray diffraction, alloys, annealing, corrosion, dielectric spectroscopy, differential scanning calorimetry, electrochemistry, heat treatment, nanocrystals, sodium hydroxide, temperature, thermal properties
The electrochemical corrosion behavior of finemet alloy at various heat treatment temperatures was investigated. Thermal behavior and structural changes were studied using differential scanning calorimetry and X-ray diffractometry, respectively. The electrochemical corrosion of amorphous and annealed samples was investigated in 0.10 M NaOH solution using electrochemical impedance spectroscopy and linear sweep voltammetery. Changes in morphology of the samples before and after corrosion were characterized using optical microscope. The results showed that structural relaxation and nanocrystallization during the heat treatment improved corrosion behavior of the alloy. The heat-treated alloy at 650 °C showed a corrosion rate of 1.37 × 10⁻⁸ A cm⁻² and a positive shift of +417 mV in the corrosion potential compared to the amorphous alloy. Also, the heat-treated alloy at 650 °C showed a higher charge transfer resistance up to 50 kΩ due to corrosion resistance, compared with amorphous sample that showed a charge transfer resistance of 0.5 kΩ.