In situ study of salt film stability in simulated pits of nickel by Raman and electrochemical impedance spectroscopies

Journal Article · Mon Dec 01 04:00:00 EST 1997 · Journal of the Electrochemical Society

DOI:https://doi.org/10.1149/1.1838173· OSTI ID:603744

Sridhar, N; Dunn, D S ^[1]

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1. Southwest Research Inst., San Antonio, TX (United States). Center for Nuclear Waste Regulatory Analyses

The changes in solution composition and the stability of a salt film in a 10 mm deep, simulated pit electrode made of nickel in a 0.5 M HCl solution were monitored as a function of applied potential using a 532 nm fiber-optic Raman system. Raman spectroscopy was able to clearly distinguish dissolved Ni(II)Cl species from the salt film of NiCl{sub 2}. Furthermore, the gradient of Ni(II)Cl in the pit was measured as a function of potential. At an applied potential of 1.5 V{sub SCE}, a NiCl{sub 2} salt film was observed at the bottom of the pit after about 5,200 s, corresponding to the first big drop in current density. The salt film was not observed below an applied potential of 0 V{sub SCE}. However, repassivation did not occur above a potential of about {minus}0.3 V{sub SCE}. The concentration gradient inside the pit decreased dramatically at {minus}0.3 V{sub SCE} and the chloride concentration at the bottom of the pit at repassivation was found to be about 17% of saturation value with respect to NiCl{sub 2} {center_dot} 6H{sub 2}O. Electrochemical impedance spectroscopy of the simulated pit electrode in the same solution at various applied potentials was used to determine the electronic properties of the salt film and the thickness of the film EIS suggested that the salt film had a dual structure, with a compact film underneath a thicker porous layer.

• Sponsoring Organization: USDOE
• OSTI ID: 603744
• Journal Information: Journal of the Electrochemical Society, Journal Name: Journal of the Electrochemical Society Journal Issue: 12 Vol. 144; ISSN 0013-4651; ISSN JESOAN
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CORROSION PRODUCTS
ELECTROCHEMICAL CORROSION
HYDROCHLORIC ACID
MORPHOLOGY
NICKEL
NICKEL CHLORIDES
PASSIVATION
PITTING CORROSION
STABILITY