الفهرس 
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Abstract
(1)A literature survey of the different theories of corrosion and passivation of metals and alloys is given with particular emphasis on the electro-chemical behaviour of nickel in aqueous media with particular emphasis on the effect of aggressive and inhibitive organic or inorganic compound.
(2)Under open-circuit conditions, the potential of the nickel electrode was followed in oxygenated aqueous solutions of different concentration of Na2CO3, NaHCO3, Na2SO4, Na2Cr04’ NaC1, NaBr, NaI, Na2W04, Na2B407, NaOH, H2SO4 and HNO3 untill steady-state values were reached. The steady-state potential (Est) varies with the anions concentration according to :
Est = a - b log Canion.
This group of anions promote the corrosion of Nickel and the extent of corrosion depends upon both the type and concentration of each anion in solution.
(3) In all solutions, the steady-state potential developed by nickel electrode move in the -ve direction as the concentration is increased showing the occurrance of corrosion.
(4)When the aggressive ions Cl, Br, I were added to each of H2SO4 and NaOH solutions in which the nickel electrode was previously equilibrated the steady-state varies with the aggressive ion concen-tration according to sigmoidal-shaped curve. The points of inflexion of these curves occurs at higher additions of the aggressive ions the higher the concentration of H2SO4 and NaOH in solutions. The two parameters are related as.
Log CH SO4
NaOH
= al + bl Log Cagg•
This relation is explained on the basis of the alteration of the structure of electrical double layer at the metal/solution interface by competitive adsorption of the two counteracting anions.
(5)Galvanostatic variation of anode potential with time at constant current densities measurements of nickel were performed in aqueous solutions of various concentrations of Na2SO4, H2SO4’ NaOH and NaCl at different current densities. It was found that the quantity of electricity required for the passivation of nickel electrodes in all solutions decreases with increasing the electrolyte. Concen-tration and/or the current density. The presence of chloride ions causes destruction of passivity on Ni with the initiation of visible pitting.
(6)Addition of increasing concentrations of mono-methyl-,monoethyl-, monobutyl-, dimethyl-, diethyl-, amines sod. Benzoate, causes inhibition of ’pitting corro-sion on the nickel electrode in NaC1 solutions, as revealed from the marked decrease in the quantity of electricity required to cause passivation similar results were found when some inorganic additives such as Na2WO4, Na2HPO4 and Na2CrO4, were introduced in sodium chloride solutions.
(7)Cyclic voltammograms and potentiodynamic polari-zation curves of the nickel electrode in construc-ted in NaC1 solutions were constructed as function of electrolyte bulk concentration, precathodization potential and scanning rate.
(8)Present results support remarks and mechanism suggested by previous works. The mode of influence of Cl- ions on the dissolution of nickel consists of two pathway.