A comparative study of the electrochemical behaviour of Algerian zinc and a zinc from a commercial sacrificial anode

Zinc is used in the oil industry as a sacrificial anode for protecting steel storage tanks from corrosion. The behaviour of a sample of zinc from the Algerian metallurgy industry (zinc A) and a commercially available zinc (zinc B) was compared in an electrolyte from storage tank drainage water. The corrosion potential measurements for zinc A confirmed that this material could be used as a sacrificial anode. The polarization curves of the two materials (zinc A and zinc B) were different, zinc A being the least polarized. Thus, the same corrosion protection could be obtained with a lower surface ratio (S _Zn/S _Fe) for Zinc A. Cyclic voltammetry curves provided evidence of a surface layer formed by dissolution products. To provide protection over extended periods of time, the zinc anode must be oversized. The two types of zinc tested were comparable.The results of the impedance spectroscopy study confirmed the previous results. The corrosion layer formed on zinc A was not prejudicial to dissolution. Hence, the properties of this zinc were found to be satisfactory for its use as a sacrificial anode.