A review on Corrosion of High Entropy Alloys: Exploring the Interplay Between Corrosion Properties, Alloy Composition, Passive Film Stability and Materials Selection

Nascimento, Camila Boldrini; Donatus, Uyime; Ríos, Carlos Triveño; Oliveira, Mara Cristina Lopes de; Antunes, Renato Altobelli

doi:10.1590/1980-5373-MR-2021-0442

Camila Boldrini Nascimento

Universidade Federal do ABC, Centro de Engenharia, Modelagem e Ciências Sociais Aplicadas, Av. Dos Estados, 09210-580, Santo André, SP, Brasil.

Uyime Donatus

Brunel University London, Brunel Centre for Advanced Solidification Technology, Uxbridge, Middlesex UB8 3PH, England.

Carlos Triveño Ríos

Universidade Federal do ABC, Centro de Engenharia, Modelagem e Ciências Sociais Aplicadas, Av. Dos Estados, 09210-580, Santo André, SP, Brasil.

Mara Cristina Lopes de Oliveira

Universidade Federal do ABC, Centro de Engenharia, Modelagem e Ciências Sociais Aplicadas, Av. Dos Estados, 09210-580, Santo André, SP, Brasil.

Renato Altobelli Antunes ^**e-mail: renato.antunes@ufabc.edu.br

Universidade Federal do ABC, Centro de Engenharia, Modelagem e Ciências Sociais Aplicadas, Av. Dos Estados, 09210-580, Santo André, SP, Brasil.

https://orcid.org/0000-0003-1540-6495

*e-mail: renato.antunes@ufabc.edu.br

Alloy composition	Structure	E_corr (mV_SCE)	i_corr (µA.cm^-2)	i_pass (µA.cm^-2)	E_pit (mV_SCE)	Additional comments	Reference
CoCrFeNi	FCC	161	15.8	4.5	244	Electrolyte: 0.5 mol.L^-1 H₂SO₄ solution at RT	²⁶26 Kao Y, Lee T, Chen S, Chang Y. Electrochemical passive properties of AlxCoCrFeNi (x = 0, 0.25, 0.50, 1.00) alloys in sulfuric acids. Corros Sci. 2010;52:1026-34. ^-a
AlCoCrFeNi	FCC + BCC	148	13.1	13.9	252	Electrolyte: 0.5 mol.L^-1 H₂SO₄ solution at RT	²⁶26 Kao Y, Lee T, Chen S, Chang Y. Electrochemical passive properties of AlxCoCrFeNi (x = 0, 0.25, 0.50, 1.00) alloys in sulfuric acids. Corros Sci. 2010;52:1026-34. ^-b
Co_1.5CrFeNi_1.5Ti_0.5	FCC	150	30	9	1089	Interdendrites rich in Ti and Ni; dendrites rich in Fe and Cr; Electrolyte: 0.5 mol.L^-1 H₂SO₄ solution at RT	²⁸28 Chou YL, Yeh JW, Shih HC. The effect of molybdenum on the corrosion behaviour of the high-entropy alloys Co1.5CrFeNi1.5Ti0.5Mox in aqueous environments. Corros Sci. 2010;52:2571-81. ^-a
Co_1.5CrFeNi_1.5Ti_0.5Mo_0.8	FCC + Cr and Mo-rich sigma phase	172	69	22	1089	Interdendrites rich in Cr and Mo; dendrites rich in Co and Ni; Electrolyte: 0.5 mol.L^-1 H₂SO₄ solution at RT	²⁸28 Chou YL, Yeh JW, Shih HC. The effect of molybdenum on the corrosion behaviour of the high-entropy alloys Co1.5CrFeNi1.5Ti0.5Mox in aqueous environments. Corros Sci. 2010;52:2571-81. ^-b
CoCrFeNiMo_0.4	FCC + Cr and Mo-rich sigma phase	-289	0.712	6	88.5	Electrolyte: 0.5 mol.L^-1 H₂SO₄ solution at RT	³⁰30 Shang X, Wang Z, Wu Q, Wang J, Li J, Yu J. Effect of Mo addition on corrosion behavior of high-entropy alloys CoCrFeNiMox in aqueous environments. Acta Metall Engl Lett. 2019;32:41-51.
CoCr₂Ni₂AlTi	Two BCC phases + Al_xCo	-240	7.24	2.45	886	Electrolyte: 0.5 mol.L^-1 H₂SO₄ solution at RT	⁴²42 Huang L, Wang X, Zhao X, Wang C, Yang Y. Analysis on the key role in corrosion behavior of CoCrNiAlTi-based high entropy alloy. Mater Chem Phys. 2021;259:124007. ^-a
Co₂Cr₂Ni₂AlTi	FCC + BCC + NiCoCr + Al_xCo	107	0.654	1.54	901		⁴²42 Huang L, Wang X, Zhao X, Wang C, Yang Y. Analysis on the key role in corrosion behavior of CoCrNiAlTi-based high entropy alloy. Mater Chem Phys. 2021;259:124007. ^-b
CoCr₂Ni₃AlTi	Two BCC phases + FCC + Al_xCo	-102	4.3	2.23	936		⁴²42 Huang L, Wang X, Zhao X, Wang C, Yang Y. Analysis on the key role in corrosion behavior of CoCrNiAlTi-based high entropy alloy. Mater Chem Phys. 2021;259:124007. ^-c
Fe₄₀Ni₂₀Co₂₀Cr₂₀	FCC	34	----	4.7	862	Electrolyte: 0.1 mol.L^-1 H₂SO₄ solution at RT	⁴⁵45 Wu P, Gan K, Yan D, Fu Z, Li Z. A non-equiatomic FeNiCoCr high-entropy alloy with excellent anti-corrosion performance and strength-ductility synergy. Corros Sci. 2021;183:109341.
Alloy composition	Structure	E_corr (mV_SCE)	i_corr (µA.cm^-2)	i_pass (µA.cm^-2)	E_pit (mV_SCE)	Additional comments	Reference
AlCuCoFeNi	FCC + BCC	-58	7.9	----	----	Cu-rich FCC phase; Al and Ni-rich BCC phase; Ti and Cr promoted grain refinement; Electrolyte: 0.5 mol.L^-1 H₂SO₄ solution at RT	⁵⁵55 Xiao DH, Zhou PF, Wu WQ, Diao HY, Gao MC, Song M, et al. Microstructure, mechanical and corrosion behaviors of AlCoCuFeNi-(Cr,Ti) high entropy alloys. Mater Des. 2017;116:438-47.-a
AlCoCuFeNiCr	BCC + FCC	-75	5.1	----	----		⁵⁵55 Xiao DH, Zhou PF, Wu WQ, Diao HY, Gao MC, Song M, et al. Microstructure, mechanical and corrosion behaviors of AlCoCuFeNi-(Cr,Ti) high entropy alloys. Mater Des. 2017;116:438-47.-b
AlCoCuFeNiTi	FCC+BCC+Laves	-253	44.8	----	----		⁵⁵55 Xiao DH, Zhou PF, Wu WQ, Diao HY, Gao MC, Song M, et al. Microstructure, mechanical and corrosion behaviors of AlCoCuFeNi-(Cr,Ti) high entropy alloys. Mater Des. 2017;116:438-47.-c
AlCoCuFeNiCrTi	FCC+BCC+Laves	-256	39.6	----	----		⁵⁵55 Xiao DH, Zhou PF, Wu WQ, Diao HY, Gao MC, Song M, et al. Microstructure, mechanical and corrosion behaviors of AlCoCuFeNi-(Cr,Ti) high entropy alloys. Mater Des. 2017;116:438-47.-d
AlCoCrFeNi	FCC + BCC + B2 (ordered BCC)	-188	30.4	2.12	1008	Annealed at 1100°C for 48 h and quenched in water; Cr enriched in the BCC phase; Electrolyte: 0.5 mol.L^-1 H₂SO₄ solution at RT	⁵⁶56 Yen C, Lu H, Tsai M, Wu B, Lo Y, Wang C, et al. Corrosion mechanism of annealed equiatomic AlCoCrFeNi tri-phase high-entropy alloy in 0.5 M H2SO4 aerated aqueous solution. Corros Sci. 2019;157:462-71.
FeCoCrNiAl_0.3	FCC	-294	17.93	2.58	901	Electrolyte: 0.5 mol.L^-1 H₂SO₄ solution at RT	⁵⁷57 Fu Y, Dai C, Luo H, Li D, Du C, Li X. The corrosion behavior and film properties of Al-containing high-entropy alloys in acidic solutions. Appl Surf Sci. 2021;560:149854.
AlCoCrFeNiTi_0.5	----	-100	0.57	26	950	Electrolyte: 0.5 mol.L^-1 H₂SO₄ solution at RT	⁵⁸58 Zhang JJ, Yin XL, Dong Y, Lu YP, Jiang L, Wang TM et al. Corrosion properties of AlxCoCrFeNiTi0.5 high entropy alloys in 0.5 M H2SO4 aqueous solution. Mater Res. 2014;18(suppl. 4):S4756-S4759.
CoFeCrNi	FCC	-250	----	4.63	----	Mn degraded passive film stability; Electrolyte: 0.1 mol.L^-1 H₂SO₄ solution at RT	⁵⁹59 Yang J, Wu J, Zhang CY, Zhang SD, Yang BJ, Emori W, et al. Effects of Mn on the electrochemical corrosion and passivation behavior of CoFeNiMnCr high-entropy alloy system in H2SO4 solution. J Alloys Compd. 2020;819:152943.-a
CoFeCrNiMn	FCC	-320	----	4.37	----		⁵⁹59 Yang J, Wu J, Zhang CY, Zhang SD, Yang BJ, Emori W, et al. Effects of Mn on the electrochemical corrosion and passivation behavior of CoFeNiMnCr high-entropy alloy system in H2SO4 solution. J Alloys Compd. 2020;819:152943.-b
(CoFeNiMn)₇₅Cr₂₅	FCC	-310	----	4.33	----		⁵⁹59 Yang J, Wu J, Zhang CY, Zhang SD, Yang BJ, Emori W, et al. Effects of Mn on the electrochemical corrosion and passivation behavior of CoFeNiMnCr high-entropy alloy system in H2SO4 solution. J Alloys Compd. 2020;819:152943.-c
(CoFeNi)₈₀Cr₂₀	FCC	-240	----	3.59	----		⁵⁹59 Yang J, Wu J, Zhang CY, Zhang SD, Yang BJ, Emori W, et al. Effects of Mn on the electrochemical corrosion and passivation behavior of CoFeNiMnCr high-entropy alloy system in H2SO4 solution. J Alloys Compd. 2020;819:152943.-d
CrMnFeNi	FCC	26	191	----	1568	Homogeneous element distribution in dendrites and interdendrites; Electrolyte: 0.5 mol.L^-1 H₂SO₄ solution at RT	⁶⁰60 Sun YP, Wang Z, Yang HJ, Lan AD, Qiao JW. Effects of the element La on the corrosion properties of CrMnFeNi high entropy alloys. J Alloys Compd. 2020;842:155825.-a
CrMnFeNiLa_0.1	FCC	73	338	----	1346		⁶⁰60 Sun YP, Wang Z, Yang HJ, Lan AD, Qiao JW. Effects of the element La on the corrosion properties of CrMnFeNi high entropy alloys. J Alloys Compd. 2020;842:155825.-b

Alloy composition	Structure		E_corr (mV_SCE)		i_corr (µA.cm^-2)		i_pass (µA.cm^-2)		E_pit (mV_SCE)		Additional comments		Reference
CoCrFeNi	FCC		-234		----		4.0		----		Electrolyte: 3.5 wt.% NaCl solution at RT		¹⁷17 Nascimento CB, Donatus U, Ríos CT, Antunes RA. Electronic properties of the passive films formed on CoCrFeNi and CoCrFeNiAl high entropy alloys in sodium chloride solution. Journal of Materials Research and Technology. 2020;9:13879-92. ^-a
CoCrFeNiAl	BCC + B2 (ordered BCC)		-300		----		6.3		667		Electrolyte: 3.5 wt.% NaCl solution at RT		¹⁷17 Nascimento CB, Donatus U, Ríos CT, Antunes RA. Electronic properties of the passive films formed on CoCrFeNi and CoCrFeNiAl high entropy alloys in sodium chloride solution. Journal of Materials Research and Technology. 2020;9:13879-92. ^-b
Al_0.3CoCrFeNi	FCC		-195		0.0835		1.24		460		Increasing Al content reduces the corrosion resistance (thicker, less stable passive film); Electrolyte: 3.5 wt.% NaCl solution at RT		²⁷27 Shi Y, Yang B, Xie X, Brechtl J, Dahmen KA, Liaw PK. Corrosion of AlxCoCrFeNi high-entropy alloys: al-content and potential scan-rate dependent pitting behavior. Corros Sci. 2017;119:33-45.
CoCrFeNiMo_0.4	FCC + Cr and Mo-rich sigma phase		-261		0.082		16		948		Electrolyte: 3.5 wt.% NaCl solution at RT		³⁰30 Shang X, Wang Z, Wu Q, Wang J, Li J, Yu J. Effect of Mo addition on corrosion behavior of high-entropy alloys CoCrFeNiMox in aqueous environments. Acta Metall Engl Lett. 2019;32:41-51.
FeCoNiCr_0.5	FCC		-319		2.36		----		453		Electrolyte: 3.5 wt.% NaCl solution at RT		³¹31 Chai W, Lu T, Pan Y. Corrosion behaviors of FeCoNiCrx (x = 0, 0,5, 1,0) multi-principal element alloys: Role of Cr-induced segregation. Intermetallics. 2020;116:106654.
AlCr_2.5FeNi₂Cu_1.6	FCC + BCC		-516		1.25		----		-21		Electrolyte: 3.5 wt.% NaCl solution at RT		³⁴34 Yang S, Yu W, Liu T, Li C, Zhang Y, Qu Y. Effect of Cr content on corrosion behavior of AlCrxFeNi2Cu1.6 high entropy alloys. Mater Res Express. 2019;6:076501.
CoCrFeMnNi	FCC		-230		0.14		----		----		Electrolyte: 3.5 wt.% NaCl solution at RT		³⁷37 Han Z, Ren W, Yang J, Tian A, Du Y, Liu G, et al. The corrosion behavior of ultra-fine grained CoNiFeCrMn high-entropy alloys. J Alloys Compd. 2020;816:152583.
Al₂CrFeCoCuTiNi	FCC + BCC		-220		13		----		----		Increasing Ni contents reduced the corrosion resistance; Electrolyte: 3.5 wt.% NaCl solution at RT		⁴⁰40 Qiu X-W, Liu C-G. Microstructure and properties of Al2CrFeCoCuTiNix high-entropy alloys prepared by laser cladding. J Alloys Compd. 2013;553:216-20. ^-a
Al₂CrFeCoCuTiNi₂	FCC + BCC		-500		67		----		----				⁴⁰40 Qiu X-W, Liu C-G. Microstructure and properties of Al2CrFeCoCuTiNix high-entropy alloys prepared by laser cladding. J Alloys Compd. 2013;553:216-20. ^-b
Al₂CrFeCo_1.0CuNiTi	----		-220		0.013		----		No passivity breakdown up to 1.2 V_SCE		Laser-cladded coatings on Q235 steel substrate; Electrolyte: 3.5 wt.% NaCl solution at RT		⁴³43 Qiu X-W. Corrosion behavior of Al2CrFeCoxCuNiTi high-entropy alloy coating in alkaline solution and salt solution. Results in Physics. 2019;12:1737-41. ^-a
Al₂CrFeCo_1.5CuNiTi	----		-510		0.074		----		No passivity breakdown up to 1.2 V_SCE				⁴³43 Qiu X-W. Corrosion behavior of Al2CrFeCoxCuNiTi high-entropy alloy coating in alkaline solution and salt solution. Results in Physics. 2019;12:1737-41. ^-b
Alloy composition	Structure		E_corr (mV_SCE)		i_corr (µA.cm^-2)		i_pass (µA.cm^-2)		E_pit (mV_SCE)		Additional comments		Reference
Co₂CrCuFeMnNi	Two FCC phases		-787		6.95		----		19		Sintered alloy; the FCC phase with higher Co content is more resistant to corrosion; Electrolyte: 3.5 wt.% NaCl solution at RT		⁴⁴44 Zhao R-F, Ben B, Cai B, Liu Z-X, Zhang G-P, Zhang J-J. Corrosion behavior of CoxCrCuFeMnNi high-entropy alloys prepared by hot pressing sintered in 3.5% NaCl solution. Results in Physics. 2019;15:102667.
CrMnFeCoNi	FCC		142.5		0.105		----		460		Cr-depleted interdendrites are the starting point for corrosion; Electrolyte: 3.5 wt.% NaCl solution at RT		⁶¹61 Ye Q, Feng K, Li Z, Lu F, Li R, Huang J, et al. Microstructure and corrosion properties of CrMnFeCoNi high entropy alloy coating. Appl Surf Sci. 2017;396:1420-6.
(CoCrFeNi)₉₅Nb₅	FCC		-128		7.23		41.3		502		Plasma sprayed coating on Q235 steel substrate; Electrolyte: 3.5 wt.% NaCl solution at RT		⁶²62 Wang W, Qi W, Xie L, Yang X, Li J, Zhang Y. Microstructure and corrosion behavior of (CoCrFeNi)95Nb5 high-entropy alloy coating fabricated by plasma spraying. Materials. 2019;12:694.
Al_0.9CoCrFeNi	FCC + BCC + B2 (ordered BCC)		-216		0.093		----		164		Electrolyte: 3.5wt.% NaCl solution at RT		⁶³63 Qiu Y, Thomas S, Fabijanic D, Barlow AJ, Fraser HL, Birbilis N. Microstructural evolution, electrochemical and corrosion properties of AlxCoCrFeNiTiy high entropy alloys. Mater Des. 2019;170:107698. ^-a
Al_0.9CoCrFeNiTi_0.5	BCC + B2 (ordered BCC) + Fe-Cr sigma phase		-347		0.310		----		184		Electrolyte: 3.5wt.% NaCl solution at RT		⁶³63 Qiu Y, Thomas S, Fabijanic D, Barlow AJ, Fraser HL, Birbilis N. Microstructural evolution, electrochemical and corrosion properties of AlxCoCrFeNiTiy high entropy alloys. Mater Des. 2019;170:107698. ^-b
CoCrFeNi₂	FCC		-290		0.129		----		320		Mo enrichment in the passive film reduces pitting corrosion susceptibility; Electrolyte: 3.5 wt.% NaCl solution at RT		⁶⁴64 Rodriguez AA, Tylczak JH, Gao MC, Jablonski PD, Detrois M, Ziomek-Moroz M, et al. Effect of molybdenum on the corrosion behavior of high-entropy alloys CoCrFeNi2 and CoCrFeNi2Mo0.25 under sodium chloride aqueous solutions. Adv Mater Sci Eng. 2018;2018:3016304. ^-a
CoCrFeNi₂Mo_0.25	FCC + HCP		-260		0.125		----		910				⁶⁴64 Rodriguez AA, Tylczak JH, Gao MC, Jablonski PD, Detrois M, Ziomek-Moroz M, et al. Effect of molybdenum on the corrosion behavior of high-entropy alloys CoCrFeNi2 and CoCrFeNi2Mo0.25 under sodium chloride aqueous solutions. Adv Mater Sci Eng. 2018;2018:3016304. ^-b
(Fe-Co-Ni)₁₅(Al-Ti-Zr)₈₅	FCC + amorphous phase		-460		2.046		----		----		Multi-component films obtained by sputtering on Si substrate; Electrolyte: 3.5 wt.% NaCl solution at RT		⁶⁵65 Wang H, Liu J, Xing Z, Ma G, Cui X, Jin G, et al. Microstructure and corrosion behaviour of AlCoFeNiTiZr high-entropy alloy films. Surf Eng. 2020;36(1):78-85. ^-a
(Fe-Co-Ni)₂₀(Al-Ti-Zr)₈₀	FCC + amorphous phase		-281		0.586		----		----				⁶⁵65 Wang H, Liu J, Xing Z, Ma G, Cui X, Jin G, et al. Microstructure and corrosion behaviour of AlCoFeNiTiZr high-entropy alloy films. Surf Eng. 2020;36(1):78-85. ^-b
(Fe-Co-Ni)₂₅(Al-Ti-Zr)₇₅	FCC + amorphous phase		-260		0.062		----		----				⁶⁵65 Wang H, Liu J, Xing Z, Ma G, Cui X, Jin G, et al. Microstructure and corrosion behaviour of AlCoFeNiTiZr high-entropy alloy films. Surf Eng. 2020;36(1):78-85. ^-c
Alloy composition	Structure		E_corr (mV_SCE)		i_corr (µA.cm^-2)		i_pass (µA.cm^-2)		E_pit (mV_SCE)		Additional comments		^Reference
Al_0.3Cr_0.5FeCoNi	FCC		-185		0.1		----		350		Increasing the Cr content in the alloy, the FCC and BCC phases became enriched with Cr; Electrolyte: 3.5 wt.% NaCl solution at RT		⁶⁶66 Yan X, Guo H, Wang W, Pang S, Wang Q, Liu Y, et al. 0.3CrxFeCoNi high-entropy alloys with high corrosion resistance and good mechanical properties. J Alloys Compd. 2021;860:158436. ^-a
Al_0.3Cr₂FeCoNi	FCC + BCC + B2 (ordered BCC)		-99		0.01		----		No breakdown up to 2 V_SCE				⁶⁶66 Yan X, Guo H, Wang W, Pang S, Wang Q, Liu Y, et al. 0.3CrxFeCoNi high-entropy alloys with high corrosion resistance and good mechanical properties. J Alloys Compd. 2021;860:158436. ^-b
TiCrVNb_0.5Al_0.5	BCC		-450		0.089		----		1950		Uniform distribution of elements without segregation; Electrolyte: 3.5 wt.% NaCl solution at RT		⁶⁷67 Li M, Chen Q, Cui X, Peng X, Huang G. Evaluation of corrosion resistance of the single-phase light refractory high entropy alloy TiCrVNb0.5Al0.5 in chloride environment. J Alloys Compd. 2020;857:158278.
Al_0.5CoCrFeNi	FCC		-570		0.17		----		130		As-cast condition; Electrolyte: 3.5 wt.% NaCl solution at RT		⁶⁸68 Lin C, Tsai H. Evolution of microstructure, hardness, and corrosion properties of high-entropy Al0.5CoCrFeNi alloy. Intermetallics. 2011;19:288-94.
CoCrFeNiMo_0.2	FCC		-192		0.00184		----		827		Mo enhances passivity (passive film composition not shown); Electrolyte: 3.5 wt.% NaCl solution at RT		⁶⁹69 Wang Q, Amar A, Jiang C, Luan H, Zhao S, Zhang H, et al. CoCrFeNiMo0.2 high entropy alloy by laser melting deposition: prospective material for low temperature and corrosion resistant applications. Intermetallics. 2020;119:106727.
(CoCrFeNi)₉₈Mo₂	FCC		-191		0.07		----		----		Aging at 900 °C for 16 h, followed by water quenching; Co and Fe-rich dendrites; Cr and Mo-rich interdendrites; Electrolyte: 3.5 wt.% NaCl solution at RT		⁷⁰70 Wang W, Wang J, Sun Z, Li J, Li L, Song X, et al. Effect of Mo and aging temperature on corrosion behavior of (CoCrFeNi)100-xMox high-entropy alloys. J Alloys Compd. 2020;812:152139. ^-a
(CoCrFeNi)₉₈Mo₃	FCC + Mo-rich precipitates		-194		0.22		----		----				⁷⁰70 Wang W, Wang J, Sun Z, Li J, Li L, Song X, et al. Effect of Mo and aging temperature on corrosion behavior of (CoCrFeNi)100-xMox high-entropy alloys. J Alloys Compd. 2020;812:152139. ^-b
AlCoCrFeNiCu_0.5	FCC + BCC		-282		1.77		----		----		Equiaxed grains (grain size smaller than 30 µm); no Cu segregation in grain boundaries; Electrolyte: artificial seawater		⁷¹71 Yu Y, Xu N, Zhu S, Qiao Z, Zhang J, Yang J, et al. A novel Cu-coped high entropy alloy with excellent comprehensive performances for marine application. J Mater Sci Technol. 2021;69:48-59.
Alloy composition		Structure		E_corr (mV_SCE)		i_corr (µA.cm^-2)		i_pass (µA.cm^-2)		E_pit (mV_SCE)		Additional comments		Reference
CoCrFeNi		FCC		-238		----		----		575		Sn increases the corrosion resistance of CoCrFeNi, whereas Al and Cu decrease; Electrolyte: 3.5 wt.% NaCl solution at RT		⁷²72 Muangtong P, Rodchanarowan A, Chaysuwan D, Chanlek N, Goodall R. The corrosion behaviour of CoCrFeNi-x (x= Cu, Al, Sn) high entropy alloy. Corros Sci. 2020;172:108740. ^-a
CoCrFeNiAl		BCC + B2 (ordered BCC)		-303		----		----		316				⁷²72 Muangtong P, Rodchanarowan A, Chaysuwan D, Chanlek N, Goodall R. The corrosion behaviour of CoCrFeNi-x (x= Cu, Al, Sn) high entropy alloy. Corros Sci. 2020;172:108740. ^-b
CoCrFeNiCu		FCC (matrix) + Cu-rich FCC (Cu segregation)		-161		----		----		-50				⁷²72 Muangtong P, Rodchanarowan A, Chaysuwan D, Chanlek N, Goodall R. The corrosion behaviour of CoCrFeNi-x (x= Cu, Al, Sn) high entropy alloy. Corros Sci. 2020;172:108740. ^-c
CoCrFeNiSn		FCC + HCP		-233		----		----		1118				⁷²72 Muangtong P, Rodchanarowan A, Chaysuwan D, Chanlek N, Goodall R. The corrosion behaviour of CoCrFeNi-x (x= Cu, Al, Sn) high entropy alloy. Corros Sci. 2020;172:108740. ^-d
CoFeMn_1.2NiGa_0.8		FCC + BCC		-416		1.11		----		790		Electrolyte: 3.5 wt.% NaCl solution at RT		⁷³73 Sun X, Du L, Lan H, Cui J, Wang L, Li R, et al. Mechanical, corrosion and magnetic behavior of a CoFeMn1.2NiGa0.8 high entropy alloy. J Mater Sci Technol. 2021;73:139-134.
Al₁₀Co₂₄Cr₁₀Fe₁₅Ni₃₄Ti₆Cu₁		FCC		-63		0.022		----		----		Fe, Co and Cr enriched in the dendrite region; Al and Ti enriched in the interdendrite region; Electrolyte: 3.5 wt.% NaCl solution at RT		⁷⁴74 Sünbul SE, Için K, Seren FZ, Sahin O, Çakil DD, Sezer R, et al. Determination of structural, isothermal oxidation and corrosion properties of Al-Co-Cr-Fe-Ni-Ti-Cu high-entropy alloy. Vacuum. 2021;187:110072.
CoCrFeNiGe_0.3		FCC		-34		0.56		2.51		1410		GeO₂ oxide present in the passive film increases the corrosion resistance with respect to CoCrFeNi HEA; Electrolyte: 3.5 wt.% NaCl solution at RT		⁷⁵75 Liu H, Tsai C. Effect of Ge addition on the microstructure, mechanical properties, and corrosion behavior of CoCrFeNi high-entropy alloys. Intermetallics. 2021;132:107167.
Co₃₀Cr₂₀Fe₃₀Ni₂₀		----		12		2.32		2.01		970		Electrolyte: 3.5 wt.% NaCl solution at RT		⁷⁶76 Yang H, Shang X, Wang L, Wang Z, Wang J, Lin X. Effect of constituent elements on the corrosion resistance of single-phase CoCrFeNi high-entropy alloys in NaCl solution. Chin Shu Hsueh Pao. 2018;54:905-10. [in Chinese]
Ni₂CrFeMo_0.2		----		-179		0.896		5.404		920				⁷⁷77 Wei L, Wu Q, Shang X, Li J, Wang J. Effect of Mo element and heat treatment on corrosion resistance of Ni2CrFeMox high-entropy alloy in NaCl solution. Chin Shu Hsueh Pao. 2019;55:840-8. [in Chinese]

Design requirements
Function	Structural component
Constraints	Acidic or sodium chloride electrolytes
Objectives	To maximize the corrosion resistance
Free variables	Component size and section area; choice of material

[1] *e-mail: renato.antunes@ufabc.edu.br