الفهرس 
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Abstract
A survey is given which summarises the previous studies on the electrode behaviour and corrosion phenomena associated with AZ91 alloy, the behaviour of AZ91 alloy was studied in 0.1 M hydrochloric acid solution free and containing different inhibitor concentrations.
Different techniques were applied to study the effect of the inhibitors ethylenediamine (EDA), propylamine (PA), diethylamine (DEA), and ethylamine (EA) on the corrosion behaviour of AZ91 alloy in 0.1 M HCl solution.
The first technique, involved the direct determination of the corrosion rate from the loss in weight of AZ91 alloy sheets immersed in 0.1 M hydrochloric acid solution free and containing different inhibitor concentrations were studied in the temperature range 20-50○C.
The second technique, potentiodynamic polarization curves of AZ91 alloy in 0.1 M hydrochloric acid in the absence and in the presence of the different organic inhibitors under investigation.
The third technique is SEM measurements. The morophological surface image of AZ91 alloy after 30 minutes dipping in 0.1 M hydrochloric acid solution free at 20○C and with 1M of EDA, PA, DEA and EA.
The individual tasks undertaken and the conclusions arrived can be classified into the following:
1) The corrosion rate decreases with increasing the inhibitor concentrations.
2) The protection efficiency increases with the increase of the inhibitor concentrations at constant temperatures.
3) The protection efficiency increases appreciably with decreasing the temperature. This means that the inhibitive action of these substances results from the physical adsorption. The weight loss of AZ91 alloy were studied also at different temperatures in the temperature range 20-50○C.
4) The calculated equilibrium constant k of the adsorption reaction for AZ91 alloy is 7500, 6900, 6250 and 2500 L mol-1 which lead to ∆G◦ = -32.50, -32.40, -32.40, and -29.88 KJ mol-1 in EDA, PA, DEA, and EA respectively. The negative value of the standard free energy of adsorption indicates the spontaneous adsorption of these inhibitors on AZ91 alloy take place.
5) Cathodic current potential curves give rise to parallel Tafel lines indicating that the hydrogen evolution reaction is activation controlled and the addition of the studied inhibitors does not modify the mechanism of this reaction.
6) The adsorbed molecules of studied compounds have no effect on the mechanism of AZ91 alloy dissolution or (hydrogen evolution reaction).
7) The value of the corrosion potential (Ecorr) is modified by the addition of compounds studied.
8) The addition of compounds studied decreases the current densities in a large domain of anodic and cathodic potentials.
9) It is clear that the corrosion attack was more pronounced in absence of additives, while by the addition of different inhibitors the film formed on AZ91 alloy surface become more protective.
10) The protective film is more pronounced for EDA, PA, DEA then EA.
The general conclusion is that all inhibitors used are excellent inhibitors for protecting for AZ91 alloy in hydrochloric acid. The sequence of the different inhibitor for protected AZ91 alloy is EDA> PA> DEA >EA.