Influence of sealing treatment on the corrosion behavior of HVAF sprayed Al-based amorphous/nanocrystalline coating
By Zhang, L. M.; Zhang, S. D.; Ma, A. L.; Hu, H. X.; Zheng, Y. G.; Yang, B. J.; Wang, J. Q.
Published in Surface and Coatings Technology
2018
Abstract
Al-based amorphous/nanocrystalline coating with a low porosity (0.42%) and a high amorphous content (80.3%) was fabricated by high velocity air-fuel spraying on aluminum alloy 2024. This thin amorphous/nanocrystalline coating with ?-Al nanocrystals precipitated in amorphous matrix displays good short-term corrosion resistance, while the corrosion resistance decreases rapidly with increased immersion time. Sealing treatment can effectively close the connecting pores and reduce the porosity defects of coating, thereby improving the corrosion resistance. Among the three selected sealants, stearic acid exhibits the best sealing effect on Al-based amorphous/nanocrystalline coating due to its good impermeability and hydrophobicity, followed by potassium dichromate and nickel acetate. The sealing mechanisms of the three sealants are discussed in terms of reactions at the coating/sealant interface and hydrophobicity of stearic acid.