An Investigation of Galvanised Iron and Iron Alloy Anodic Electrodes Performance Used for Corrosion Protection of Crude Oil Storage Tanks

Crude oil can carry various high–impurity products which are inherently corrosive. Such highly corrosive media are Sulfur (S) and free water (H2O).These materials degradation in the mechanical properties of the crude oil storage tanks walls leads to reduction in thickness.

There are two basic methods used to provide cathodic protection (C.P) to steel tanks. By far the most common and simplest method of protection is a “sacrificial anode system” and “impressed current system”. Aluminum (Al), Zinc (Zn) and Magnesium (Mg) anodes are commonly used in the sacrificial anode system method.

In this work, two laboratory experiments are conducted by using two samples: (A)- anode electrode of Galvanized iron and (B)- anode electrode of iron alloy metal while the cathode electrode of carbon steel are used for both experiments. The electrodes are immersed in an electrochemical corrosion cell containing crude oil taken from the West Qurna oil field in Basra Governorate, southern of Iraq, for the purpose of measuring the corrosion rates of the anode electrodes and then compare the result with the corrosion rate of Zinc electrode, which is mainly used for cathodic protection of oil storage tanks.

Results showed that the corrosion rate of the iron anodic electrode is (0.56 mm/y) which is higher than the corrosion rate of Zinc electrode is (0.365 mm/y), while the corrosion rate for Galvanized iron electrode is (0.01 mm/y).

Conclusion confirmed that the anode electrode of iron alloy metal can be used in the manufacture for the cathodic protection (C.P) of oil storage tanks, which is much cheaper than the Zinc electrode is currently used.