Cailiao gongcheng (Mar 2023)
Corrosion resistance of boron nitride nanoplatelet reinforced chemically bonded ceramic coatings
Abstract
To improve the corrosion resistance of 304 stainless steel, boron nitride nanoplatelet (BNNP) reinforced chemically bonded ceramic coatings with lateral sizes of 3 μm and 300 nm were prepared on the substrate surface by the slurry method. The surface hydrophobic properties of BNNP coatings with different lateral sizes were characterized by SEM and optical contact angle measurement. The corrosion behavior of the coatings under simulated seawater solution was revealed by an electrochemical workstation. The effects of BNNP lateral size and content on the coatings' microscopic morphology and corrosion protection properties and their mechanisms were investigated. The results show that the surface wetting angle of the coatings increases with the addition of BNNP, the coatings of both lateral sizes have excellent hydrophobicity at 1.0%(mass fraction, the same below) BNNP, and the coatings with 300 nm BNNP have significant improvement, which increase the surface wetting angle of the coatings from 38° to 96.972°. The addition of BNNP improves the coating quality, fills the pores and cracks inside the coatings, and BNNP has good hydrophobicity, which actively contributes to the improvement of the hydrophobicity of the coatings. And 300 nm BNNP has a better sealing effect, creating more nuclei and filling the voids between alumina particles and the adhesive. The coatings with the addition of 300 nm BNNP at 1.0% have the highest low-frequency impedance and corrosion potential of 22500 Ω·cm2 and 0.344 V, respectively, and the corrosion current density reaches the lowest value of 1.12×10-7 A/cm2. The coatings prepared on the surface of the substrate create a physical barrier that effectively hinders the intrusion of corrosive media into the substrate. Compared with the original coatings, the surface morphology of the coatings with BNNP is denser after corrosion, reducing the defects such as pores and cracks in the coatings. BNNP is chemically stable and has good corrosion resistance, which can further delay and retart the corrosion reaction in the coatings and prevent the contact of the substrate with the corrosive medium. The addition of 300 nm BNNP has smaller lateral sizes and a wider distribution range, thus better impeding the expansion of corrosion paths. There are fewer defects such as corrosion pits and holes on the surface. Therefore, the coatings with the addition of 300 nm BNNP have a better effect on hindering the expansion of corrosion paths.
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