Optimization of the corrosion property of a high entropy alloy using response surface methodology Modupeola Dada ⇑ , Patricia Popoola, Olufemi Aramide Chemical, Metallurgical and Materials Engineering, Tshwane University of Technology, Pretoria, 0183, South Africa article info Article history: Received 8 May 2020 Received in revised form 21 May 2020 Accepted 24 May 2020 Available online xxxx Keywords: Predictive Modelling Corrosion High Entropy Alloy Laser Additive Manufacturing Sodium Chloride abstract Laser Additive Manufacturing was used to fabricate AlTiCrFeCoNi high entropy alloy and the corrosion properties of the alloy were investigated in 3.5 wt% NaCl solution. The tests were conducted via poten- tiodynamic polarization at room temperature in a three-electrode cell system with a platinum wire as the counter electrode, Ag/AgCl as the reference electrode and the high entropy alloy as the working elec- trode. The electrochemical parameters; polarization resistance and corrosion rate were determined. These parameters help decide the corrosion resistance capability of the alloy. A model was developed using response surface methodology, and central composite design tools as an optimization method. The experimental and theoretical data using design of experiment’s analysis of variance were used to pre- dict the optimal corrosion properties and determine the relationship between the laser processing parameters and the corrosion behaviour of the alloy. The electrochemical tests were carried out on sam- ples fabricated from the set of parameters; laser power and scanning velocity varied between 1400 and 1600 W at 8–12 mm/s derived from previous studies. Results from the model showed that the optimum laser parameter to yield the best corrosion properties in the 3.5 wt% NaCl medium was at 1500 W and 10 mm/s, with a corrosion rate of 0.003445 mm/yr and polarization resistance 0.00255 X.cm 2 . The the- oretical and the experimental data were in good agreement which shows that response surface method- ology is an effective tool for modelling and optimizing the high entropy alloy’s properties. Ó 2020 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International Sympo- sium on Nanostructured, Nanoengineered and Advanced Materials. 1. Introduction The surface morphology of High Entropy Alloys (HEAs) is a very important property to consider for aerospace applications because it governs the corrosion resistance of the advanced material in ser- vice. Corrosion is a material degradation process which occurs on the surface of the material because of an electrochemical reaction with the environment [1]. There are several surface engineering techniques used to inhibit corrosion such as thermal spraying, electroplating, anodizing to name a few, however, these processes are faced with limitations such as large consumption of materials, time and energy [2]. The Cu-free AlCoCrFeNi High Entropy Alloy (HEA) system has been extensively studied in literature with the addition of Ti known for its large atomic radius; the Ti alloying ele- ment has shown good influence in the system’s mechanical prop- erties. Nevertheless, this alloy system is widely fabricated using conventional methods [3–5]. Laser Additive Manufacturing (LAM), on the other hand, has been reported to be an effective technique in producing HEAs with enhanced corrosion properties attributed to its conservation of time, material and energy. Hence, in our previous work, before and after optimization of the laser processing parameters, the AlTiCrFeCoNi HEA with FCC and BCC phase structures was reported to have several attractive properties for aerospace applications such as excellent hardness and strength at elevated temperatures [6,7]. In this paper, the corrosion beha- viour of this HEA was further studied using surface response methodology. Qui et al. [8] fabricated HEAs using LAM and they reported that the alloys had good corrosion resistance in 3.5 wt% NaCl solution and recommended the alloys for coatings on Q235 steels. Cui et al. [9] mentioned that the HEAs prepared by LAM were subjected to ultrasonic surface mechanical rolling treatments which showed higher corrosion resistance than those without treatments but generally the alloys had excellent corrosion resis- tance attributed to the manufacturing technique. Sha et al. [10] argued that the HEAs prepared by LAM in different compositions https://doi.org/10.1016/j.matpr.2020.05.618 2214-7853/Ó 2020 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International Symposium on Nanostructured, Nanoengineered and Advanced Materials. ⇑ Corresponding author. E-mail address: dadadupeola@gmail.com (M. Dada). Materials Today: Proceedings xxx (xxxx) xxx Contents lists available at ScienceDirect Materials Today: Proceedings journal homepage: www.elsevier.com/locate/matpr Please cite this article as: M. Dada, P. Popoola and O. Aramide, Optimization of the corrosion property of a high entropy alloy using response surface methodology, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2020.05.618