ELECTROCHEMICAL AND MORPHOLOGICAL STUDY OF ZN-MN ALLOYS DEPOSITED FROM BORIC ACID ELECTROLYTE ONTO THE CARBON STEEL FOR CORROSION PROTECTION

M. Y. Haciibrahimoglu, A. Yavuz

Abstract: Boric acid electrolyte was used for the deposition of zinc and Zn-Mn films from the electrolyte having variable pH onto carbon steel substrate. The deposition and dissolution mechanisms of the Zn-Mn alloys were explained. The coatings were obtained potentiostatically by applying -1.5 V, then the morphological and corrosion behaviours of resulting films were studied. There was no reduction of manganese in acidic or neutral borate solution; hence, the coating from these solutions contained only zinc metal. The film obtained from alkaline borate electrolyte was Zn-Mn alloy including around 5wt. % manganese. Zn-Mn alloy is in the form of amorphous structure and only zinc coatings have well crystalline structure. While chloride solution is accelerated the pitting corrosion on steel surface, coated steel (with either Zn or Zn-Mn films) from borate based solution, is prevented from pitting corrosion as passivation of modified electrodes occurs in artificial seawater (3.5wt. % aqueous NaCl solution). Corrosion rate of bare steel is higher than that of the modified electrodes. Electrodeposition of Zn and Zn-Mn films from boric acid solution can not only protect steel from pitting corrosion but also give higher corrosion resistivity.

Keywords: Zinc-Manganese Alloy, Electrodeposition, Boric Acid Electrolyte, Amorphous Structure, Corrosion, Passivation

DOI: https://doi.org/10.15623/ijret.2016.0511013