Elsevier

Applied Surface Science

Volume 440, 15 May 2018, Pages 861-872
Applied Surface Science

Full Length Article
Effects of sulfate and nitrate anions on aluminum corrosion in slightly alkaline solution

https://doi.org/10.1016/j.apsusc.2018.01.108Get rights and content

Highlights

  • The corrosion of Al is influenced by the anions, concentration and anodic potentials.

  • The chemical adsorption of SO42- and NO3- changes the composition of Al passive film.

  • The change of solution structure in concentrated electrolytes impedes Al dissolution.

Abstract

The corrosion mechanisms and kinetics of AA1085 in Li2SO4 and LiNO3 aqueous rechargeable lithium-ion battery electrolytes were investigated at pH 11 using chronoamperometry. The corrosion kinetics of AA1085 is controlled by the electrolyte concentration level and the anodic potentials. AA1085 is susceptible to crystallographic pitting corrosion in Li2SO4 electrolytes. The rates of pit nucleation and pit growth both decreased at higher Li2SO4 concentrations or at lower anodic potentials. AA1085 passivates against pitting corrosion in LiNO3 electrolytes due to the formation of a thick, uniform corrosion product layer. The growth rate of the passive film was slightly enhanced by increasing the electrolyte concentration and anodic potentials. X-ray photoelectron spectroscopy spectra showed the formation of a thin sulfate-incorporated passive film on the electrode, which comprises Al2(SO)418H2O, Al(OH)SO4 and Al(OH)3, before the occurrence of pitting growth in 2 M Li2SO4 electrolyte. The thick corrosion product layer formed in 5 M LiNO3 electrolyte was composed of Al(OH)3 and AlOOH. Raman spectroscopy on deionized water, LiOH solution, Li2SO4 and LiNO3 electrolytes depicted changes of solution structure with increasing electrolyte concentration. The influence of extrinsic and intrinsic factors on the corrosion kinetics of AA1085 in Li2SO4 and LiNO3 electrolytes at pH 11 are discussed in detail.

Introduction

Aluminum finds a wide range of applications due to its distinct properties such as low density, high energy density and considerable corrosion resistance. Investigating the mechanism and the kinetics of aluminum corrosion, especially the localized corrosion of aluminum, is of interest because the corrosion often leads to sudden failure or impairs the function of the component. In lithium-ion batteries, commercial purity AA1085 is widely used as a current collector material [1] and so is of particular interest. Corrosion of the aluminum current collector irreversibly increases the internal battery resistance, contaminates electrolyte, attacks the electrode material and consequently degrades the battery performance, life and even safety [2], [3], [4]. The recently developed aqueous rechargeable lithium-ion battery (ARLB) technology has raised concerns with the risk of current collector corrosion in aqueous battery electrolytes. To ensure the chemical stability of specific cathode active materials, the electrolytes of ARLB are usually adjusted to slightly alkaline conditions which are beyond the stability window of aluminum (pH 4–8) as predicated by the Pourbaix diagram [5]. Prior work identified 2 M Li2SO4 and 5 M LiNO3 aqueous solutions as high performing ARLB electrolytes [6]. The highly concentrated salt solutions add more complexities to the stability of aluminum in ARLB systems.

Attempts have been made to understand the effects of sulfate and nitrate anions on the corrosion of high-purity aluminum, but there are some discrepancies in the literature. Poggi et al. claimed that addition of 0.01 to 0.1 M SO42- mitigates the corrosion of high-purity aluminum in slightly alkaline solutions by a competitive adsorption mechanism [7]. It was claimed that the sulfate anions significantly retard the crystallization of gibbsite from amorphous aluminum oxide in aqueous solutions [8]. Using electrochemical noise analysis, Na and Pyun described that the presence of SO42- and NO3- enhances the corrosion of high-purity aluminum in aqueous alkaline solution [9]. Branzoi reported that addition of 0.05 M and 0.1 M hydroxyl anions in 1 M NaNO3 solution leads to extensive localized attack on high-purity aluminum [10]. While it was also claimed that nitrate combining with other inorganic anions effectively inhibits aluminum corrosion in alkaline solutions [11]. To the best of our knowledge, no literature has described the effects of SO42- and NO3- on the corrosion of commercial purity aluminum in slightly alkaline solutions and so the corrosion kinetics of this common aluminum current collector alloy in slightly alkaline ARLB electrolytes is not clear. The highly concentrated Li2SO4 and LiNO3 electrolytes used in ARLB, which provide desirable stability of a lithium anode and high ionic conductivity of the electrolyte, may intensify the effects of sulfate and nitrate anions on aluminum corrosion. Yamada et al. reported that highly concentrated LiFSA-based electrolytes effectively suppress aluminum corrosion up to 4.5 V versus Li+/Li [12]. The inhibiting effect of the concentrated electrolytes was explained by the declined activity of free solvent molecules. Understanding the relationship between the electrochemical stability of aluminum and the structure of concentrated aqueous electrolytes may help explain the role of SO42- and NO3- on aluminum corrosion. The purpose of the present work is to describe the influence of sulfate and nitrate anions on the corrosion kinetics of AA1085 in slightly alkaline solutions relevant to ARLB conditions. This will support corrosion management in the design of aqueous based energy storage systems and the extensive use of aluminum and aluminum alloys in many other industrial applications where exposure to similar conditions may occur.

Section snippets

ARLB electrolyte

The aqueous electrolytes were prepared by dissolving specific weights of LiOH (anhydrous, 98%, Alfa Aesar) in de-ionized water to adjust the pH to 11, followed by addition of lithium salts to target concentration of 0.1 M, 0.5 M and 2 M Li2SO4 (anhydrous, 99.7%, Alfa Aesar) and 0.1 M, 2 M and 5 M LiNO3 (anhydrous, 99.98%, Alfa Aesar) equivalent. These target compositions were based on the optimal electrolyte compositions with additional iterations at lower concentrations [5]. The solutions were

Stability window of solutions measured by LSV

The operating voltage range of ARLB is confined to the stability window of the electrolyte. The theoretical gas evolution potentials can be calculated from thermodynamic principles as EH+/H2=-0.059pH and EO2/H2O=1.23-0.059pH, where EH+/H2 is the hydrogen evolution potential and EO2/H2O is the oxygen onset potential. At pH 11, the theoretical stability window of ARLB electrolyte is 1.23 V and exists between −0.846 V and 0.384 V vs Ag/AgCl (sat’d KCl) reference electrode. The stability windows

The role of anion adsorption on corrosion kinetics

In alkaline solutions, the aluminum oxide passive film and aluminum matrix dissolve due to the attacking of hydroxyl ions by the following reactions [34], [35],Al2O3(s)+2OH-+3H2O2Al(OH)4-2Al(s)+2OH-+6H2O(l)2Al(OH)4-+3H2(g)

Pitting corrosion initiates preferably at surface defect sites and microstructural heterogeneities. The inevitable existence of Fe as impurity element in AA1085 results in the formation of Al3Fe intermetallic particles that exhibit more noble electrochemical potentials than

Conclusions

The corrosion kinetics of AA1085 in slightly alkaline ARLB Li2SO4 and LiNO3 electrolytes was investigated using chronoamperometry within the stability window of each electrolyte. AA1085 is prone to pitting corrosion in Li2SO4 electrolytes at the anodic potential of 0.85 V. In LiNO3 electrolytes, AA1085 is protected from pitting corrosion due to repassivation. The kinetics of pitting corrosion and repassivation process on AA1085 is controlled by the electrolyte concentration level and the

Acknowledgements

Electron microscopy was carried out at UW-Milwaukee Biological Sciences Microscopy Center. X-ray photoelectron spectroscopy and Raman spectroscopy was conducted at the UW-Milwaukee Advanced Analysis Facility.

References (44)

  • X.R. Yu et al.

    Auger parameters for sulfur-containing compounds using a mixed aluminum-silver excitation source

    J. Electron Spectros. Relat. Phenomena.

    (1990)
  • J.C. Klein et al.

    Surface characterization of model urushibara catalysts

    J. Catal.

    (1983)
  • M.L. Doche et al.

    Electrochemical behaviour of aluminium in concentrated NaOH solutions

    Corros. Sci.

    (1999)
  • B. Deng et al.

    Dependence of critical pitting temperature on the concentration of sulphate ion in chloride-containing solutions

    Appl. Surf. Sci.

    (2007)
  • P. Zhao et al.

    Effect of homogenization treatment conditions on the recrystalization behavior of Al-1.2Mn aluminum alloy sheets

  • T.C. Hyams et al.

    Corrosion of aluminum current collectors in high-power lithium-ion batteries for use in hybrid electric vehicles

    J. Electrochem. Soc.

    (2007)
  • A.H. Whitehead et al.

    Current collectors for positive electrodes of lithium-based batteries

    J. Electrochem. Soc.

    (2005)
  • A.M. Beccaria et al.

    Aluminum corrosion in slightly alkaline sulfate solutions

    Corrosion

    (1987)
  • F. Branzoi et al.

    The influence of different aggressive anions on the electrochemical behaviour of aluminium in sodium nitrate aqueous solutions

    Mater. Corros.

    (2000)
  • T.S. Humphries, Low Toxic Corrosion Inhibitors for Aluminum in Fresh Water, Technical report, Report No. NASA-TP-1279,...
  • Y. Yamada et al.

    Corrosion prevention mechanism of aluminum metal in superconcentrated electrolytes

    ChemElectroChem.

    (2015)
  • C. Wessells et al.

    Investigations of the electrochemical stability of aqueous electrolytes for lithium battery applications

    Electrochem. Solid-State Lett.

    (2010)
  • Cited by (19)

    • Realizing reversible storage of trivalent aluminum ions using VOPO<inf>4</inf>·2H<inf>2</inf>O nanosheets as cathode material in aqueous aluminum metal batteries

      2021, Journal of Alloys and Compounds
      Citation Excerpt :

      The galvanostatic charge/discharge tests of the VOPO4·2H2O cathode were also carried out using other aluminum salts (AlCl3·6H2O, Al(NO3)3·9H2O, Al2(SO4)3·18H2O) aqueous solutions as electrolytes (Fig. S3). The results show that the electrochemical reactions are irreversible or inactive probably due to the difficulty in achieving reversible Al platting/striping on anode in these electrolytes [55–57]. The galvanostatic charge/discharge tests using 1 and 2 mol L−1 Al(CF3SO3)3 electrolytes demonstrate that increasing the concentration of the electrolyte can improve the coulombic efficiency of the batteries since the free water molecules are less in the high-concentration electrolyte (Fig. S4) [17].

    • Electroless deposition via galvanic displacement as a simple way for the preparation of silver, gold, and copper SERS-active substrates

      2021, Colloids and Surfaces A: Physicochemical and Engineering Aspects
      Citation Excerpt :

      Only a few reports deal with the nitrate ions behavior at the open-circuit potential to the best of our knowledge. In the form of a slightly alkaline solution, it is mostly concerned as a pitting inhibitor, since corrosion of Al stops after the formation of a thick passivation layer [21,22]. However, corrosion susceptibility of metals and alloys is strongly influenced by the precipitates and/or metallic inclusions in aluminum (e.g. Cu, Fe, Zn, Mg-rich phases) as a result of distinct electrochemical properties of galvanic couples (intermetallic phases vs. surrounding matrix) under open-circuit potential [23,24].

    • A promising hybrid additive for enhancing the performance of alkaline aluminum-air batteries

      2021, Materials Chemistry and Physics
      Citation Excerpt :

      Li et al. studied the effects of sulfate anion on aluminum corrosion in slightly alkaline solution. They claimed that sulfate anion was involved in the formation of cation-selective diffusion layers on aluminum surface, which greatly retarded the pitting corrosion of aluminum [48]. Combining the advantages of zinc-type inhibitor and sulfate anion for the anti-corrosion properties of aluminum in alkaline medium, zinc sulfate (ZnSO4) is tentatively investigated in this work, aiming at the mitigation of aluminum corrosion and the promotion of the discharge performance of the battery.

    • Prominent inhibition efficiency of sodium nitrate to corrosion of Al-based amorphous alloy

      2020, Applied Surface Science
      Citation Excerpt :

      They also demonstrated that there is a threshold concentration for nitrate to inhibit the pit embryo formation rate in HCl solutions [16]. Li et al. suggested that the formation of a corrosion product layer on AA1085 is accelerated in LiNO3 electrolyte[17]. The film serves as a barrier layer which impedes the ingression of aggressive anions and protects aluminum from rapid pitting corrosion.

    View all citing articles on Scopus
    View full text