الفهرس 
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Abstract
Aluminum anodes have been widely used as sacrificial anodes in the cathodic protection of on-shore and off shore structures. However there are conditions in which these anodes become passivated or become susceptible to some localized or unwanted corrosion, which influences their efficiency. Addition of alloying elements such as Zn, Si, Sn and In have improved the efficiency of the anodes.
In the present Work, the effect of Indium and Zinc addition on the electrochemical properties of the Aluminum will be investigated. Indium addition helps to maintain the satisfying performance of the aluminum sacrificial anodes. PMI (Positive Material Identification) was used to check the chemical composition of the aluminum anodes after casting. Electrochemical tests according to NACE standard methods were carried out to evaluate the anodic behavior, potential and current capacity of the anodes.
Ten Aluminum alloys with different chemical composition were produced, all the produced alloys were submitted to investigations in the present work. The aluminum alloy containing the following composition (Al+4.5% Zn+0.02 In) showed the maximum current capacity of 2120 A.H/Kg, So when comparing the current capacity of this alloy to the current capacity obtained from Aluminum commercial pure anode, which gave 1221 A.H/Kg, we found that the current capacity has increased with 73%. But when increasing the amount of indium beyond (0.02% In) the current capacity starts to decline and the anode starts to dissolve, and small particles from the anode starts to disintegrate hence these particles doesn’t participate in the cathodic protection reaction and the anode loses its efficiency. Also increasing the amount of Zinc beyond 4.5% doesn’t have a major effect on the current capacity of the anode. So the best aluminum anode alloy was produced was the alloy with chemical composition (AL-4.5% Zn- 0.02% In). Microstructure investigation revealed the presence of second phase precipitates in the grain boundaries and inside the grain itself, which is inferred to be responsible for the increase of the current capacity of the Al anode by creating defects in the formed oxide layer.