Effect of Electrolyte Flow on the Corrosion Behavior of Magnesium Alloy AZ31B

Abstract

The influence of electrolyte flow (3.5 wt% NaCl) on the corrosion behavior of magnesium alloy AZ31B was investigated by using a rotating disc electrode. An increase in flow rate (wall shear stress) of the electrolyte over the alloy surface caused a sharp decrease in the corrosion resistance of AZ31B. This was due to the formation of a progressively thinner and more porous Mg(OH)2 film and due to the physical removal of the film by the flow-induced shear stress, reaching a plateau at ca. 2,500 rpm. An empirical equation that models the AZ31B corrosion rate as a function of rpm was proposed. Surface characterization indicated that the nonuniform degradation of the alloy surface was dominated by filiform corrosion and an eventual lateral growth of stable pits at higher rpms. With an increase in rpm, the surface area influenced by the corrosion also increased.