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Initiation and Inhibition of Pitting Corrosion in Alkali Solutions under potentiostatic polarization conditions
Author(s) -
Abd El Haleem S. M.
Publication year - 1979
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/maco.19790300905
Subject(s) - pitting corrosion , corrosion , ion , chromate conversion coating , inorganic chemistry , chemistry , alkali metal , halogen , polarization (electrochemistry) , materials science , metallurgy , alkyl , organic chemistry
The variation of the critical pitting potential of a zincalloy was studied in aerated NaOH solutions as a function of the concentration of the aggressive ions, Cl − , Br − and I − . Curves with segmented nature were obtained when E pitting was plotted versus logarithm of the halogen ion concentrations. Initiation of pitting corrosion was discussed on the basis of formation of complex halo‐compounds with the oxides/hydroxides that constitute the passive surface film. Addition of chromate, phosphate and carbonate ions to the halogen‐containing solutions causes the shift of the critical pitting potential in the noble direction, accounting for increased resistance to pitting attack. Nitrite‐ion additions contribute with the halogen ions in the destruction of the passive film. Sufficient concentrations of the carbonate ions cause complete inhibition of pitting corrosion.