Preparation of ZrV conductive-corrosion resistant conversion coating on AZ91 magnesium alloy via film-forming regulation and the coupling mechanism of additives

Controlling substrate dissolution and film growth is critical to preparing high-quality coating. This study regulates surface structure and elemental composition by co-depositing elements and additives to prepare a conductive and corrosion-resistant ZrVC on AZ91 magnesium alloy. First-principles and Mott–Schottky analyses indicate that zirconium doping enhances electronic conductivity by increasing carrier concentration. The roles of co-deposited elements, oxidants, pH buffers, and promoters are evaluated through elemental composition and microstructural characterisation. The coating exhibits a contact resistance of 0.566 Ω·cm², a polarisation resistance increased by approximately 600 times, and a self-corrosion current density reduced by three orders of magnitude, with no corrosion detected after 132 h of neutral salt spray testing. The interfacial reaction mechanisms during coating formation and corrosion are further elucidated through DRT analysis.