الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
1-The introduction included a literature survey of the different theories of corrosion and corrosion inhibition. The electrochemical behaviour of aluminium and aluminium alloys in neutral solutions was given with particular emphasis on the effect of aggressive as well as inhibitive anions.
2-Cyclic galvanostatic polarization curves were constructed for aluminium and its four alloys (samplesl, II, III and IV, whose compo-sition is given in table 1) in 0.1M Na2SO4 solutions devoid of and containing aggressive Cl ions as well as inhibitive inorganic
Cr042’ HPO42’ Mo042- and HCO3 anions.
a-The presence of the alloying elements affects the rate of the anodic dissolution of aluminium in 0.1M Na2SO4 solutions, and shifts the oxygen evolution potential to lower values.
b-The thickness of oxide films formed on the
different electrodes surface at a potential
Summary and conclusion 114
of 1.OV and before oxygen evolution decreases in the order:
sample IV > sample III > Al > sample I > sample II This indicates that Cu is superior to Mg (at percent composition used) as an alloying element for retarding the anodic dissolution of Al 0.1M Na2SO4 solution.
C- The concentration of Cl ions required to,
just, initiate pitting corrosion of Al and its alloys increases in the order:
sample III <sample I <sample IV <Al <Sample II This reflect the order of increased tenden-cies to resist pitting corrosion of the diff-erent electrodes.
d- The concentration of the inhibitive anions required to recall the polarization curves that reported in Cif-free 0.1M Na2SO4 solutions increases inthe order:
Cr042- >HPO42> Mo042- >HCO3
This indicates that Cr042- has the higher inhibiting efficiency, while HCO3 is the least effective inhibitor.
Summary and conclusion 115
The extent of inhibiting action of these anions depends upon the electrode type and alloy composition.
3-Potentiodynamic anodic polarization curves of Al and its four alloys were reported in 0.1M Na2SO4 solutions devoid of and containing increasing concentrations of Cl ions. It was found that at a certain Cl ion concen-tration, which depends on the quantity and nature of the alloying element, the current flowing the passive range, increases sudd-enly at some definite potentials indicating the destruction of the passivating oxide film and the intiation of pitting. The pitting corrosion potential varies with the logarithm molarity of Cl- ion according to:
= a1 - b2 log C Epitt. agg.
4-Inhibition of the pitting corrosion of alloy (sample IV) was tried by using the sodium salts of chromate, molybdate, mono-hydrogen phosphate and bicarbonate. These anions causes the shift of the critical pitting
Summary and conclusion 116
potential into the noble direction according
to:
Epitt•= a3 + b3 log Cinh
5-Cyclic voltammograms were constructed for Al and its four alloys electrod in Na2S°4 solution as a function of electrolyte concen-tration and voltage scanning rate.
6-Increasing the sulphate ion concentration causes:
a-Shift of the peak potential (peak A) of alloys (samples I and II) towards more positive values; while the peak potential (Epeak) of the main anodic peak (peak D) of alloys (samples III and IV) is shifted into the negative direction, according to the equation:
Epeak = a4 + b4 log C.
b-Shift of the peaks current (ipeak) of alloys (samples I and II) towards more negative values, according to the equation:
log Speak r al - Si log C.
Summary and conclusion 117
while the peaks current of alloys (samples III and IV) have the reverse order according to the equation:
log132 log C. ipeak a2
The above findings may be expected, taken into consideration the standard potentials of aluminium and the alloying elements Mg and Cu.
7- Increasing the sweep rate results in a marked enlargement of the current densities flowing along the whole range of the CVs, for all the cases studied.