STUDIES ON THE ElECTROCHEMICAl BEHAVIOR OF AlUMINUM AND ALUMINUM AlLOYS IN DIFFERENT MEDIA

Abstract

This Thesis is aimed at studying the electrochemical and corrosion behavior of aluminum metal (99.92%) that produced by Egyptalum. The addition of nickel as alloying element due to its high corrosion resistance and mechanical properties, was expected to improve the aluminum mechanical properties, which plays an important role in its corrosion behavior. Since the addition of element to another may obeys the phase diagram, which determines the kind of the phases that present from the change of the percentage of the alloying elements at different temperatures. So specific percentages were taken into account that cause deferent effects in the behavior of the resulted alloys. These percentages, represent the following areas of the phase diagram of aluminum- nickel system: . 1 - below solid solubility region, up to 0.03% Ni. 2 - above solid solubility region

3 -the eutectic region with 6% Ni at 913° kin which, NiA13 phase (p phase) is present together with aluminum (a phase). NiAh phase make as a fiber, which improve the mechanical properties of aluminum. 4- above the eutectic region, in which the percentage ofNiAb increases.

The following measurements were performed on the studied alloys:

-The uniform corrosion behavior of pure aluminum and pure nickel in NaOH solution was studied by the potentiodynamic techniques. In this solution the anodic sweep of pure aluminum exhibits passive region for long rang of the otential. This is due to the formation of passive layer of aluminum oxide.