Tenfold Enhancement of Wear Resistance by Electrosynthesis of a Nanostructured Self‐Lubricating Al2O3/Sn(S)MoS2 Composite Film on AlSiCu Casting Alloys

Enhancing tribological performance through nanostructure control is crucial for saving energy and improving wear resistance for diverse applications. We introduce a new electrochemical approach that integrates aluminum (Al) anodization, tin alternating current (AC) electrodeposition, and anodic MoS 2 electrosynthesis for fabricating nanostructured Al 2 O 3 /Sn(S)MoS 2 composite films on AlSiCu casting alloys. Our unique process uses Sn‐modified MoS 2 deposition to form robust solid lubricant MoS 2 –SnS electrodeposits within the nanochannels and microsized voids/defects of anodic alumina matrix films on the base materials, resulting in a bilayered Al 2 O 3 /SnSMoS 2 and MoS 2 –SnS–Sn composite film. The AC‐deposited Sn enhances conductivity in the anodic alumina matrix film, acts as catalytic nuclei for Sn@SnS@MoS 2 core‐shell nanoparticles and a dense top layer, and serves as a reductant for the direct synthesis of hybrid solid lubricant MoS 2 –SnS from MoS 3 by anodic electrolysis of MoS 4 2− ions. The resulting nanocomposite film provides a two‐fold increase in lubricity (friction coefficient (COF) μ = 0.14 ⇒ 0.07) and a ten‐fold improvement in wear resistance (COF μ < 0.2) compared to conventional Al 2 O 3 /MoS 2 film formed by anodizing and reanodizing. The effectiveness of the Al 2 O 3 /Sn(S)MoS 2 composite is further validated through real automotive engine piston tests.