Preparation and Properties of Mo/Ti/Sn Conductivity Conversion Coatings on 6063 Aluminum Alloy

ABSTRACT Conductivity chromium‐free conversion coatings on aluminum substrates were achieved by utilizing Na 2 SnO 3 and Mo/Ti solutions. The composition and morphology of the coatings were characterized using XPS, SEM, EDS, AFM, and Raman spectroscopies. The corrosion behavior of the coatings in 3.5‐wt% NaCl solution was investigated through a dynamic potential polarization method and EIS analysis. Mott–Schottky and UV–Vis analyses were used to determine the semiconductor properties of the coatings, including carrier concentration and band gap. The results revealed that the main components of the coating were Al 2 O 3 , SnO 2 , MoO 3 , and MoO 2 and the coating presented a double‐layer structure, including a transition layer close to the substrate and a compact layer on the surface. The coating also exhibited the properties of a p‐type semiconductor. The electrical contact resistance value of adding Na 2 SnO 3 decreased from 0.4331 to 0.1343 Ω/in 2 (in 200 psi), while the band gap decreased from 2.281 to 2.232 eV.