Corrosion behaviour of a rapidly solidified Al87.4Co7.9Ce4.7 layer prepared by large area electron beam irradiation

•Amorphous layer formed by LAEB was more corrosion resistant than as-cast alloy.•Cracks in the treated layer exposed the untreated substrate to the electrolyte.•Compositional heterogeneities in the amorphous layer caused localised corrosion.•Subsurface melting and subsequent eruption generated craters and particles. In this study, a bulk crystalline glass forming alloy with the composition of Al87.4Co7.9Ce4.7 (at.%) was rapidly solidified by large area electron beam (LAEB) surface melting of an as-cast starting material. Glancing angle XRD results show that, providing appropriate processing parameters are selected, a predominantly amorphous layer ∼5μm thick can be produced. However, under non-optimum processing conditions treated layers are compositionally inhomogeneous and comprise, in the main, crystalline regions. LAEB treated layers also exhibit a degree of surface cracking as well as micron-sized localised craters and ejected particles formed during electron beam irradiation. Potentiodynamic polarisation tests show that treated layers exhibit enhanced corrosion resistance compared to the as-cast bulk alloy; with the predominantly amorphous layer having the lowest current density. Examination of corroded samples following potentiodynamic tests reveals that cracks limit the effectiveness of the treated layer as a barrier to corrosion.