Preparation and performance of KH-SDDTC@HNTs/EP composite coatings based on magnesium alloy AZ31

This study aims to enhance the corrosion resistance of AZ31 magnesium alloy, a functionalized halloysite nanotube self-healing coating (KH-SDDTC@HNTs/EP) was fabricated on the AZ31 magnesium alloy substrate. A kind of functionalized halloysite nanotubes/epoxy composite coatings (KH-SDDTC@HNTs/EP) loaded with corrosion inhibitor was designed and prepared. Firstly, sodium diethyldithiocarbamate (SDDTC) was encapsulated in halloysite nanotubes (HNTs) by negative pressure method. Then, the functional halloysite nanotubes were hydrophobic modified by silane coupling agent. Finally, the functional halloysite nanotubes/epoxy composite coatings were prepared on AZ31 magnesium alloy surface by doping epoxy resin (EP) with SDDTC as nano filler. Experimental results show that the loading rate of SDDTC on functionalized halloysite nanotubes is 3.91%, with a release rate of 99.99% at 540 min. For the KH-SDDTC@HNTs/EP coating (20% KH-SDDTC@HNTs content) at |Z|0.01 Hz, the coating exhibits a maximum resistance of 1.27×1010 Ω·cm², a corrosion current density of 1.02×10−1 A•cm−² and a protection efficiency of 99.995%. The innovation of this work lies in constructing environmentally-friendly hydrophobic and self-healing KH-SDDTC@HNTs/EP coatings. A dual protection mechanism of “physical barrier” and “active repair” is provided for magnesium alloys, which effectively prolongs the service life of protective coatings and provides a new strategy for long-term corrosion protection of magnesium alloys.