Preparation and characterization of Nd-doped double-layer silane anticorrosion coating on AZ91D magnesium alloy surface

Abstract

Magnesium alloys have found widespread application as engineering and functional materials in automobile, aerospace, electronics, and biomedical industries. However, these alloys are susceptible to corrosion, and the development of new anticorrosion coatings on Mg alloys surface is urgently needed. In this work, pristine and doped double-layer silane coatings were applied to the AZ91D Mg alloy surface in order to improve its corrosion resistance properties in a 3.5% NaCl solution. The doped silane coatings consisted of KH-550 as the bottom layer and Nd(NO3)3-doped bis-(γ-triethoxysilylpropyl)-tetrasulfide (BTESPT) as the top layer. The effect of Nd(NO3)3 concentration on the corrosion inhibition properties of silane coatings was studied, and the highest corrosion resistance was achieved when the Nd(NO3)3 concentration was 5 × 10−3 mol/L. Compared to the pristine coating, the doped coating had enhanced hydrophobicity with a water contact angle of 108° and, to the best of our knowledge, one of the lowest corrosion current densities (1.51 × 10−2 μA/cm2) reported to date for treated AZ91D. These significant improvements were attributed to the presence of the Si-O-Nd network in the doped coating, leading to the uniform and homogeneous nature and excellent anticorrosion properties of Nd-doped silane coating.