Effect of pore characteristics on corrosion behavior of Al-based amorphous alloy coatings
High-velocity air-fuel spray(HVAF)technology was used to prepare two kinds of Al-based amorphous alloy coatings with high porosity(HP)of 1.36%and low porosity(LP)of 0.86%.The effects of porosities on the corrosion behavior of Al-based amorphous alloy coatings were studied.The porosities and microstructures of the coatings were analyzed by scanning electron microscope(SEM)and X-ray diffraction(XRD)combined with three-dimensional X-ray tomography(3D XRT).The corrosion properties of the coatings were studied by electrochemical testing system and contact angle measuring instrument.The passive film components of the two coatings were analyzed by X-ray photoelectron spectroscopy(XPS).The results show that the self-corrosion current density(Icorr)and pitting potential(Epit)of the LP coatings are 3.0×10-6 A/cm2 and-0.40 V,respectively.The Icorr and Epit for HP coatings are 6.0×10-6 A/cm2 and-0.47 V,respectively,signifying that the LP coating has better resistance to the localized corrosion;the charge transfer resistance(Rct)of LP coatings is about twice than that of HP coating;the LP coating has a larger contact angle,which proves that LP coating has better hydrophobicity and stronger corrosion resistance;the contents of RE2O3 in the passive film formed on the LP coating are larger,which further indicates that LP coating has better corrosion resistance.
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