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Mechanism of growth of the open circuit insulating Oxide films on valve metals
Author(s) -
Abd ElRahman H. A.
Publication year - 1991
Publication title -
materialwissenschaft und werkstofftechnik
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.285
H-Index - 38
eISSN - 1521-4052
pISSN - 0933-5137
DOI - 10.1002/mawe.19910220907
Subject(s) - electrolyte , oxide , ionic strength , capacitance , metal , chemistry , ionic bonding , adsorption , kinetics , materials science , salt (chemistry) , open circuit voltage , field strength , inorganic chemistry , analytical chemistry (journal) , electrode , metallurgy , electrical engineering , ion , voltage , chromatography , physics , organic chemistry , quantum mechanics , aqueous solution , magnetic field , engineering
The kinetics of growth of the open circuit insulating oxide films on Hf, Ta, Nb, Zr and Al were studies in many salt solutions using potential and capacitance measurements. The effect of salt type and concentration, oxygen concentration, temperature and surface pretreatment on the growth kinetics were also investigated. In all cases, the potential and the reciprocal capacitance were found to increase linearly with logarithm of time. It is assumed that the oxide film grows via the solid state mechanism under the influence of highly enough electric field strength to cause the ionic migration. The field is created as a result of the adsorption of the electrolyte anions onto the metal oxide surface. The estimated field strengths (H ≈ 10 6 V cm −1 ) are in favour with the proposed mechanism. The results showed also that the growth rate constant is a function of the field strength.