Enhanced wettability of zinc passivation layer by coating organic–inorganic multilayers

Zinc Cr(III) passivation layer (Zn‐PL) could effectively protect NdFeB materials from corrosion. However, long‐term exposure of Zn‐PL to ambient atmosphere would reduce its wettability spontaneously, which hinders or deteriorates the adhesion of post‐deposited materials. To solve this issue, a multilayer developed by layer‐by‐layer assembly approach was designed, and alumina sol and silica sol were prepared. A polyacrylic acid (PAA) layer was firstly deposited on Zn‐PL to remove the preabsorbed organic carbon and form poly(zinc acrylate). Then, Al 2 O 3 and SiO 2 sol–gel layers were sequentially assembled on PAA‐coated Zn‐PL. As a result, the hydrophobic Zn‐PL turns into super‐hydrophilic by coating organic–inorganic multilayers, which is attributed to the surface enrichment of hydrophilic hydroxyl groups and increases surface roughness. Furthermore, the super‐hydrophilic surface displays excellent adhesion property without the negative effect on its other properties, which highlights a good prospect for a wide application of NdFeB or other potential materials.