**1. Introduction**

Currently, cryolite molten salt electrolysis is the only method for smelting aluminum [1]. During the electrolysis of molten cryolite, the cathode carbon block exhibits some corrosion properties; especially, sodium (Na) permeates into the cathode carbon block and causes the expansion of the carbon block, which is the main cause of the cathode damage and failure [2].

Many studies on cathodic carbon blocks have focused on wettable cathodes, among which TiB<sup>2</sup> has become a research hotspot, because it is characterized by good wettability to liquid aluminum, low resolution, resistance to electrolyte erosion, and good electrical conductivity [3]. At present, many domestic and foreign studies on TiB<sup>2</sup> and its composites mainly focus on TiB<sup>2</sup> ceramic cathodes [4,5], TiB2-carbon adhesive coating [6–8], TiB<sup>2</sup> layer prepared by plating in molten salt [9–11], TiB<sup>2</sup> non-carbon adhesive coating [12], TiB<sup>2</sup> coating prepared via chemical vapor deposition [13], TiB<sup>2</sup> coating prepared via selfspreading high-temperature synthesis TiB<sup>2</sup> coating [14], and TiB<sup>2</sup> coating prepared via plasma spraying [15].

In recent years, our research group has conducted numerous studies on the TiB<sup>2</sup> coating preparation via atmospheric plasma spraying (APS) and has achieved certain results. Through several orthogonal experiments on spraying parameters, the best process conditions for the coating preparation have been obtained [16]. The influence of mechanical properties has been studied [17]. The current study mainly investigates the microstructure of TiB<sup>2</sup> coating prepared via APS under optimal process conditions and the wettability and corrosion resistance of TiB<sup>2</sup> coating in a molten-salt electrolytic aluminum system.

**Citation:** Yang, B.; Peng, R.; Zhao, D.; Yang, N.; Hou, Y.; Xie, G. Performance of TiB<sup>2</sup> Wettable Cathode Coating. *Minerals* **2022**, *12*, 27. https://doi.org/10.3390/ min12010027

Academic Editors: Kenneth N. Han, Shuai Wang, Xingjie Wang and Jia Yang

Received: 4 November 2021 Accepted: 22 December 2021 Published: 24 December 2021

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**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

#### **2. Materials and Methods**

#### *2.1. Materials*

The TiB<sup>2</sup> powder used in the experiment was obtained from a certain chemical industry research institute in Shenyang (TiB<sup>2</sup> ≥ 98.5%), with a particle size of −325–+400 mesh (38–45 µm). For aluminum electrolysis, a graphite cathode carbon block was adopted as the matrix (the specification was 100 mm × 100 mm × 30 mm); it was provided by an aluminum factory in Yunnan and needed to be polished and sandblasted in advance.
