International Journal of Hydrogen Energy, Vol.45, No.32, 15805-15813, 2020
Corrosion of pure and milled Mg17Al12 in "model" seawater solution
The corrosion behavior of pure Mg17Al12 and the effect of ball milling in presence of additives (i.e. graphite (G) and magnesium chloride (MgCl2)) are evaluated in 3.5 wt% NaCl aqueous solution using electrochemical polarization and impedance measurements. Pure Mg17Al12 and milled Mg17Al12 without additives and with MgCl2 present an open current potential (OCP) of -1.2 V/SCE while Mg17Al12 + G shows a slightly higher OCP (+10% maximum). Mg17Al12 corrodes with low kinetics and an increase of corrosion rate for the milled Mg17Al12 is observed. The corrosion current densities (J(corr)) derived from the Tafel plots, exhibit their corrosion reactivity as follow: Mg17Al12 < Mg17Al12 5h < Mg17Al12 G 5h < Mg17Al12 + MgCl2 5h. Electrochemical impedance spectroscopy (EIS) results are in good agreement with the measured J(corr). Randles circuit models are established for all samples to explain their surface behavior in the aqueous NaCl solution. The variation of the fitted parameters is attributed either to the effect of ball milling or to the effect of the additive. Our results are helpful in elucidating the effect of ball milling and the additives. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.