Fig. 13

a, b The schematic presentation of the as-prepared PEHA-SS coating and Zr-CrCC+PEHA-SS coating deposited on the Al-Si7-Mg0.3 surface. c, d Schematical presentation of the corrosion along the scribe of the PEHA-SS-coated sample and Zr-CrCC+PEHA-SS-coated sample after prolonged exposure in the salt spray chamber. While the scribe on the PEHA-SS coating was filled with corrosion products, the Zr-CrCC coating redeposited within the scribe, and no corrosion attack was observed. e Schematical presentation of the chemical composition of the PEHA-SS and the interface with the substrate showing the formation of the corrosion products within the scribe. f Schematical presentation of the Zr-Cr-CC + PEHA-SS multilayer chemical composition and interface with the substrate showing the mechanism of enhanced adhesion, redeposition of Zr-CrCC and consequent repassivation along the scribed area. For the sake of simplicity, the heterogeneity of the substrate comprising matrix with eutectic phase with IMPs was not considered here since it was already described in section Deposition and characterisation of Zr-Cr conversion coating.