The influence of alloy microstructure on corrosion resistance and other properties of coatings formed by microarc oxidation

The influence of the initial microstructure of the aluminium alloy Al–12Si on the corrosion resistance of the microarc oxidation (MAO) coating has been studied. It has been established that the corrosion rate of samples with MAO-coating on an alloy with an ultrafine-grained (UFG) structure increases by 5.6 ... 11.6 times depending on the modes of the MAO process in relation to samples with a coating, but with a coarse-grained structure. It is assumed that this effect is associated with unrecorded small-scale porosity, the proportion of which in the MAO layer on samples with an UFG structure is higher. •The microarc oxidation (MAO) process have been used for forming of the coating on the aluminum alloy samples.•The samples in the initial coarse-grained (CG) state and in the ultrafine-grained (UFG) state were subjected to MAO process.•The characteristics of MAO layers largely depend on the microstructure of the base material.•The corrosion rate of coated UFG-samples is 5.6–11.6 times higher compared to coated CG-samples.