A localized study on the influence of surface preparation on the reactivity of cast Al-7Si-1Fe and Al-7Si-2Cu-1Fe alloys and their effect on cerium conversion coating deposition

The spontaneous triggering of cerium-based conversion coating deposition occurs due to active micro-galvanic couple induced local rise in pH at cathodic sites. Since surface preparations prior treatment modify the reactivity or extent coupling between anodic and phases, they are crucial importance. While many past works have studied effect various including alkaline etching and/or acid pickling their parameters on resulting coating, very few studies focus changes from preparation. Moreover, most use high Cu containing AA2024, related work other alloys scarce. In this study, two model cast Al-7Si-1Fe Al-7Si-2Cu-1Fe been created obtain a relatively homogeneous microstructure different activity intermetallics Fe-rich IM ?-Al5FeSi Cu-rich ?-Al2Cu. Changes state each alloy monitored with AFM-SKPFM after subjecting them four specific preparations: (1) Mechanical polishing (2) NaOH (3) + HNO3 Pickling (4) H2SO4 correlations made localized deposit observations.