Corrosion resistance of a superhydrophobic polypropylene coating on magnesium alloy AZ31

Abstract

Purpose

To improve the corrosion resistance of magnesium alloys, the construction of protective coatings is necessary to extend the service life of Mg-based materials.

Design/methodology/approach

SiO₂ nanoparticles modified by dodecyltrimethoxysilane (DTMS) were added to the PP and a superhydrophobic Mg(OH)₂/PP-60mSiO₂ composite coating was fabricated on the surface of AZ31 magnesium alloy via the hydrothermal method and subsequently the immersion treatment.

Findings

Hydrophilic SiO₂ nanoparticles become hydrophobic after modified by DTMS, showing a higher dispersibility in xylene. By incorporating modified SiO₂ nanoparticles into the composite PP coating, the hydrophobicity of the layer was enhanced, resulting in a contact angle of 166.3° and a sliding angle of 3.4°. It also improved the water repellency and durability of the coating. Furthermore, the intermediate layer of Mg(OH)₂ significantly strengthened the bond between the PP layer and the substrate. The Mg(OH)₂/PP-60mSiO₂ composite coating significantly enhances the corrosion resistance of the magnesium alloy by effectively blocking the infiltration of the corrosion anions during corrosion. The corrosion current density of the Mg(OH)₂/PP-60mSiO₂ composite coating is approximately 8.23 × 10^–9 A·cm^-2, which can achieve a magnitude three times lower than its substrate, making it a promising surface modification for the Mg alloy.

Originality/value

The composite coating effectively and durably enhances the corrosion resistance of magnesium alloys.

Citation

Zhang, S., Li, M., Li, B., Zhao, H. and Wang, F. (2024), "Corrosion resistance of a superhydrophobic polypropylene coating on magnesium alloy AZ31", Anti-Corrosion Methods and Materials, Vol. ahead-of-print No. ahead-of-print. https://doi.org/10.1108/ACMM-03-2024-2989