Cathodic Protection of Oil Pipelines by Aluminum Alloys

In the present work, a series of aluminum alloys have produced as candidate sacrificial anodes materials to use in the protection of oil pipelines that pass through the AL-FAO region area in Southern of Iraq, where the soil is enriched with the chlorides ions. The production of these alloys consists of alloying the pure aluminum with different weight percentages of Zn and Mg. These produced alloys microstructurally and electrochemically characterized to use as cathodic protection anodes of oil pipelines. Generally, all the produced Al-alloys provide well protection for steel pipelines with different efficiencies. They give a lower current density (1.51 – 12.36 μA/cm^²) in comparison with the used Mg-alloy. The produced (C-alloy: 5.5 wt%Zn, 10wt%Mg) clearly satisfied the criteria where a uniform weight loss rate accompanied with a noticeable current density. It gives (12.36 μA/cm^²) with linear and uniform weight loss. The reason behind such behavior, was attributed to the chemical composition of this alloy that develops a set of phases such as ß(Al2Mg)-phase in addition to the τ(Mg32(AlZn)49)-phase that exists in a larger amount this time as compared with τ(Mg32(AlZn)49)- phase which developed in B-alloy (5.5 Zn + 8 Mg)%wt. The higher content of phase above plays an important role in breaking down the protective oxide film that can form on the Al-alloys surface and as a result, increasing its effectiveness as a sacrificial anode by a uniform increasing of dissolution (i.e. corrosion). The produced C-alloy was found superior than the Mg-alloy that is now originally used in cathodic protection of oil pipelines in Southern Iraq.