Preparation and application of a waterborne acrylic copolymer-siloxane composite: improvement on the corrosion resistance of zinc-coated NdFeB magnets

Abstract

In order to improve the corrosion resistance of the zinc coating on NdFeB, a novel siloxane functionalised waterborne acrylic copolymer (APC-Si) was prepared by combining the self-produced waterborne acrylic copolymer coating (APC) with the silica sol precursor. The silica sol precursor was prepared by hydrolysis from siloxane with side chains and then introduced into the APC to in situ generate the silica sol. The effect of the silica sol on the anti-corrosion property of the thin acrylic copolymer coating was investigated by potentiodynamic polarisation, electrochemical impedance spectroscopy (EIS) and a neutral salt spray (NSS) test. The morphology and composition of the coatings as well as the particle size of the silica sol were studied by scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS) and transmission electron microscopy (TEM). The results showed that the compactness and the crosslinking density of the APC-Si were improved due to the interaction of APC and the silica sol. The corrosion resistance of the APC-Si increased 5–6 times, and the corrosion current density of zinc-coated NdFeB coated with APC-Si decreased significantly compared with that coated with APC.