Passivity and pitting of single-phase FeCoNi-Cr-Al compositionally complex alloys: An Al-Cr Third Element Effect in sulfuric acid containing chloride

Debashish Sur; Kaitlyn L. Anderson; Junsoo Han; John R. Scully

doi:10.1016/j.corsci.2025.113402

Passivity and pitting of single-phase FeCoNi-Cr-Al compositionally complex alloys: An Al-Cr Third Element Effect in sulfuric acid containing chloride

Debashish Sur
, Kaitlyn L. Anderson
, Junsoo Han
, John R. Scully

Corrosion Science & Technology

Research output: Contribution to journal › Article › peer-review

3 Scopus citations

Abstract

The synergistic effects of Al on Cr(III) passivation in a family of single phase FCC (FeCoNi)_100-x-yCr_xAl_y (at%) compositionally complex alloys (CCAs), where x = (10, 13, 16) and y = (0, 3, 6, 9) were investigated for both passivation and resistance to chloride induced local breakdown of the passive film. Homogenized solid solution alloys containing Cr and small amounts of Al achieved excellent passivation compared to Cr containing CCAs alone by enriching both Cr and some Al on the surface in chloride containing sulfuric acid solutions. For example, an alloy containing 10 at% Cr and 9 at% Al demonstrated better repassivation as well as resistance to chloride induced pitting corrosion than a CCA containing just 10 at% Cr. Further, compared to 304L stainless steel containing 20 at% Cr, a CCA containing 16 at% Cr and 3 at% Al attained better passivation and improved pitting resistance in 1 M NaCl + 0.1 M H₂SO_4(aq.) solution. Two underlying mechanisms are proposed to explain the beneficial effects on passivity. The observed Al-Cr synergy can be understood as a type of third element effect. Enhanced passivation is enabled by surface enrichment of Cr promoted by Al enrichment, resulting in mixed solid-solution Al(III)-Cr(III) oxides. Further, the study also considers the influence of Cr–Cr pairs brought about be Al addition, facilitated by chemical short-range ordering.

Original language	English
Article number	113402
Journal	Corrosion Science
Volume	258
DOIs	https://doi.org/10.1016/j.corsci.2025.113402
State	Published - Jan 2026

Funding

The authors gratefully acknowledge partial funding from the Office of Naval Research (ONR) through the Multidisciplinary University Research Initiative (MURI) program (award: N00014–20–1–2368) with program manager Dr. D. Shifler. Thanks to J.P. Couzinie at Institut de Chimie et des Matériaux Paris-Est (ICMPE) for casting and B. Redemann at Johns Hopkins University (JHU) for solution heat treating these alloys. D.S. extends his gratitude to the UVA-SEAS Endowed Olsen Graduate Fellowship (2024) as well as the UVA-DMSE Endowed Olsen Graduate Fellowship (2020) for partial funding of this work. J.H. and AESEC experiments conducted by D.S. were also supported by the French government's “France 2030” initiative through the PEPR-DIADEM (Priority Research Programs and Equipment - Integrated Devices for Accelerating the Deployment of Emerging Materials) program, managed by the French National Research Agency (Agence Nationale de la Recherche, ANR), n◦ANR-23-PEXD-0006. The authors gratefully acknowledge partial funding from the Office of Naval Research (ONR) through the Multidisciplinary University Research Initiative ( MURI ) program (award: N00014–20–1–2368 ) with program manager Dr. D. Shifler. Thanks to J.P. Couzinie at Institut de Chimie et des Matériaux Paris-Est (ICMPE) for casting and B. Redemann at Johns Hopkins University (JHU) for solution heat treating these alloys. D.S. extends his gratitude to the UVA-SEAS Endowed Olsen Graduate Fellowship (2024) as well as the UVA-DMSE Endowed Olsen Graduate Fellowship (2020) for partial funding of this work. J.H. and AESEC experiments conducted by D.S. were also supported by the French government’s “France 2030” initiative through the PEPR-DIADEM (Priority Research Programs and Equipment - Integrated Devices for Accelerating the Deployment of Emerging Materials) program, managed by the French National Research Agency (Agence Nationale de la Recherche, ANR), n◦ANR-23-PEXD-0006 .

Keywords

AESEC
CCAs
EIS
Passivity
Pitting
Third element effect

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title = "Passivity and pitting of single-phase FeCoNi-Cr-Al compositionally complex alloys: An Al-Cr Third Element Effect in sulfuric acid containing chloride",

abstract = "The synergistic effects of Al on Cr(III) passivation in a family of single phase FCC (FeCoNi)100-x-yCrxAly (at\%) compositionally complex alloys (CCAs), where x = (10, 13, 16) and y = (0, 3, 6, 9) were investigated for both passivation and resistance to chloride induced local breakdown of the passive film. Homogenized solid solution alloys containing Cr and small amounts of Al achieved excellent passivation compared to Cr containing CCAs alone by enriching both Cr and some Al on the surface in chloride containing sulfuric acid solutions. For example, an alloy containing 10 at\% Cr and 9 at\% Al demonstrated better repassivation as well as resistance to chloride induced pitting corrosion than a CCA containing just 10 at\% Cr. Further, compared to 304L stainless steel containing 20 at\% Cr, a CCA containing 16 at\% Cr and 3 at\% Al attained better passivation and improved pitting resistance in 1 M NaCl + 0.1 M H2SO4(aq.) solution. Two underlying mechanisms are proposed to explain the beneficial effects on passivity. The observed Al-Cr synergy can be understood as a type of third element effect. Enhanced passivation is enabled by surface enrichment of Cr promoted by Al enrichment, resulting in mixed solid-solution Al(III)-Cr(III) oxides. Further, the study also considers the influence of Cr–Cr pairs brought about be Al addition, facilitated by chemical short-range ordering.",

keywords = "AESEC, CCAs, EIS, Passivity, Pitting, Third element effect",

author = "Debashish Sur and Anderson, \{Kaitlyn L.\} and Junsoo Han and Scully, \{John R.\}",

note = "Publisher Copyright: {\textcopyright} 2025 Elsevier Ltd",

year = "2026",

month = jan,

doi = "10.1016/j.corsci.2025.113402",

language = "English",

volume = "258",

journal = "Corrosion Science",

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publisher = "Elsevier",

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T1 - Passivity and pitting of single-phase FeCoNi-Cr-Al compositionally complex alloys

T2 - An Al-Cr Third Element Effect in sulfuric acid containing chloride

AU - Sur, Debashish

AU - Anderson, Kaitlyn L.

AU - Han, Junsoo

AU - Scully, John R.

PY - 2026/1

Y1 - 2026/1

N2 - The synergistic effects of Al on Cr(III) passivation in a family of single phase FCC (FeCoNi)100-x-yCrxAly (at%) compositionally complex alloys (CCAs), where x = (10, 13, 16) and y = (0, 3, 6, 9) were investigated for both passivation and resistance to chloride induced local breakdown of the passive film. Homogenized solid solution alloys containing Cr and small amounts of Al achieved excellent passivation compared to Cr containing CCAs alone by enriching both Cr and some Al on the surface in chloride containing sulfuric acid solutions. For example, an alloy containing 10 at% Cr and 9 at% Al demonstrated better repassivation as well as resistance to chloride induced pitting corrosion than a CCA containing just 10 at% Cr. Further, compared to 304L stainless steel containing 20 at% Cr, a CCA containing 16 at% Cr and 3 at% Al attained better passivation and improved pitting resistance in 1 M NaCl + 0.1 M H2SO4(aq.) solution. Two underlying mechanisms are proposed to explain the beneficial effects on passivity. The observed Al-Cr synergy can be understood as a type of third element effect. Enhanced passivation is enabled by surface enrichment of Cr promoted by Al enrichment, resulting in mixed solid-solution Al(III)-Cr(III) oxides. Further, the study also considers the influence of Cr–Cr pairs brought about be Al addition, facilitated by chemical short-range ordering.

AB - The synergistic effects of Al on Cr(III) passivation in a family of single phase FCC (FeCoNi)100-x-yCrxAly (at%) compositionally complex alloys (CCAs), where x = (10, 13, 16) and y = (0, 3, 6, 9) were investigated for both passivation and resistance to chloride induced local breakdown of the passive film. Homogenized solid solution alloys containing Cr and small amounts of Al achieved excellent passivation compared to Cr containing CCAs alone by enriching both Cr and some Al on the surface in chloride containing sulfuric acid solutions. For example, an alloy containing 10 at% Cr and 9 at% Al demonstrated better repassivation as well as resistance to chloride induced pitting corrosion than a CCA containing just 10 at% Cr. Further, compared to 304L stainless steel containing 20 at% Cr, a CCA containing 16 at% Cr and 3 at% Al attained better passivation and improved pitting resistance in 1 M NaCl + 0.1 M H2SO4(aq.) solution. Two underlying mechanisms are proposed to explain the beneficial effects on passivity. The observed Al-Cr synergy can be understood as a type of third element effect. Enhanced passivation is enabled by surface enrichment of Cr promoted by Al enrichment, resulting in mixed solid-solution Al(III)-Cr(III) oxides. Further, the study also considers the influence of Cr–Cr pairs brought about be Al addition, facilitated by chemical short-range ordering.

KW - AESEC

KW - CCAs

KW - EIS

KW - Passivity

KW - Pitting

KW - Third element effect

UR - https://www.scopus.com/pages/publications/105019368678

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DO - 10.1016/j.corsci.2025.113402

M3 - Article

AN - SCOPUS:105019368678

SN - 0010-938X

VL - 258

JO - Corrosion Science

JF - Corrosion Science

M1 - 113402

ER -

Passivity and pitting of single-phase FeCoNi-Cr-Al compositionally complex alloys: An Al-Cr Third Element Effect in sulfuric acid containing chloride

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