EIS study of oxidation heat‐treatment effects on corrosion behavior of Ni10Cu11Fe6Al metallic inert anode inside molten calcium chloride salt

Abstract

In this research, the effects of oxidation heat‐treatment on the high‐temperature corrosion behavior of Ni10Cu11Fe6Al (wt%) alloy was investigated as a new inert anode in titanium electrolytic production. The alloys were prepared using vacuum induction melting (VIM) process and then exposed to the electrolysis in calcium chloride molten salt at 900 °C at −1.6 V versus graphite reference electrode for different immersion times. The cross‐section and surface of the alloys were characterized using scanning electron microscope (SEM), and their electrochemical behavior was investigated by electrochemical impedance spectroscopy (EIS). The results showed that the oxidized alloys have the greater number of porosities compared to those of the unoxidized alloys. Thus, the nickel‐based alloy became more sensitive to pitting resulting from oxidation. The corrosion penetration depth reached about 400 µm after 16 h of electrolysis for the oxidized alloys while being nearly 213 µm for the unoxidized alloys, which indicates the corrosion penetration depth increased by oxidation. Therefore, the oxidation during the electrolysis inside the molten salt offers better results for this alloy.

Impact of NaCl impurity on corrosion of 316 L steel in molten nitrate salts for thermal energy storage: An electrochemical study

“…Furthermore, electrochemical techniques have been widely used in the study of molten salt corrosion, [ 16–22 ] and have been proved to be effective in understanding corrosion mechanisms, kinetics, and corrosion process. Fernández et al [ 23 ] investigated the positive effect of alumina‐forming on corrosion behavior of austenitic stainless steel using EIS method in molten nitrate salts.…”

“…Apart from this, the evaluation of the corrosion behavior of SS in molten nitrate salts containing high-content chloride impurity is limited. There are few investigations on the corrosion behavior of austenitic SS in molten nitrate salts containing chloride higher than 1 wt% by electrochemical measurements, especially electrochemical impedance spectroscopy (EIS), which is regarded as the effective and reliable technique for corrosion monitoring in CSP plants according to Encinas-Sánchez et al [16] Furthermore, electrochemical techniques have been widely used in the study of molten salt corrosion, [16][17][18][19][20][21][22] and have been proved to be effective in understanding corrosion mechanisms, kinetics, and corrosion process. Fernández et al [23] investigated the positive effect of alumina-forming on corrosion behavior of austenitic stainless steel using EIS method in molten nitrate salts.…”

Localized Heat Treatment to Improve the Formability of Steel Pipes for Hydraulic Applications: Process Design and Mechanical Characterization

“…Microstructural and mechanical properties were similarly modified and improved on other types of materials, like nickel-based coatings [14] and titanium alloys [15,16]. Furthermore, several other types of applications different from the heat treatments were carried out by means of the induction heating, like melting and casting of copper [17] and nickel alloys [18], technological processes implying large deformations [19,20], and innovative welding processes [21,22]. By the present paper, authors proposed experimental methods to quantify the impact on the mechanical properties of a localized induction heat treatment performed on steel hose fittings for hydraulic applications.…”