Electrochemical stability corrosion data

D. Moosbauer, S. Zugmann, M. AmereUer, H. J. Gores, J. Chem. Eng. Data 2010, 55, 1794-1798. Effect of ionic liquids as additives on lithium electrolytes Conductivity, electrochemical stability, and aluminum corrosion. 

Moosbauer D, Zugmann S, Amereller M, Gores HJ (2010) Effect of ionic liquids as additives tm lithiiun electrolytes conductivity, electrochemical stability, and alttttiinttm corrosion. J Chem Eng Data 55 1794—1798... 

Environmental tests have been combined with conventional electrochemical measurements by Smallen et al. [131] and by Novotny and Staud [132], The first electrochemical tests on CoCr thin-film alloys were published by Wang et al. [133]. Kobayashi et al. [134] reported electrochemical data coupled with surface analysis of anodically oxidized amorphous CoX alloys, with X = Ta, Nb, Ti or Zr. Brusic et al. [125] presented potentiodynamic polarization curves obtained on electroless CoP and sputtered Co, CoNi, CoTi, and CoCr in distilled water. The results indicate that the thin-film alloys behave similarly to the bulk materials [133], The protective film is less than 5 nm thick [127] and rich in a passivating metal oxide, such as chromium oxide [133, 134], Such an oxide forms preferentially if the Cr content in the alloy is, depending on the author, above 10% [130], 14% [131], 16% [127], or 17% [133], It is thought to stabilize the non-passivating cobalt oxides [123], Once covered by stable oxide, the alloy surface shows much higher corrosion potential and lower corrosion rate than Co, i.e. it shows more noble behavior [125]. 

Summary. Scanning tunneling microscopy (STM) provides new possibilities to explore the link between the structure and the properties of thin oxide overlayers (passive films) formed electrochemically on well-defined metal surfaces. Passive oxide films protect many metals and alloys against corrosion. A better understanding of the growth mechanisms, the stability, and the degradation of passive films requires precise structural data. Recently, new results on the atomic structure of passive films have been obtained by STM. The important questions of crystallinity, epitaxy and the nature of defects have been addressed. Data on the structure of passive films on Ni, Cr, Fe, Al, and Fe-Cr alloys are reviewed with enq>hasis on atomically resolved structures. Ihe perspectives of future developments are discussed. 

Because these alloys have been commercially developed, the full compositional, heat treatment and corrosion testing details are not available. It is difficult to identify the particular effects of R additions on the corrosion resistance of these alloys from the data shown, because of the absence of a systematic variation in the particular R addition or concentration. There is however, sufficient evidence in table 5 to suggest that R additions play a role in improving the corrosion resistance of Mg casting alloys, but it is difficult to draw conclusions regarding the nature of that role. As with other alloys, the corrosion resistance of Mg alloys is generally associated with the stability, solubility and defect structure of the naturally occurring oxide film, and the tendency for the various phases in the microstructure to act as local anodes and cathodes. Unfortunately there is no evidence in the literature to indicate whether or not R additions modify the properties of the surface oxide film on the cast Mg alloys or alter the electrochemical balance of the microstructure. 

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