Effect of bionic hydrophobic structures on the corrosion performance of Fe-based amorphous metallic coatings

Abstract Fe-based amorphous metallic coatings (AMCs) were prepared by the activated combustion−high velocity air fuel (AC − HVAF) coating method. A micro/nanoscale hydrophobic surface based on the lotus effect was constructed on the AMCs by chemical etching and surface modification, and the controllable preparation of bionic hydrophobic structures was realized by optimizing the chemical etching time and etching concentration. The influence of surface treatment on the corrosion resistance of the coatings was analyzed by electrochemical testing, and the correlation between the hydrophobicity of the coating structure and its corrosion resistance was determined. Results showed that the surface of the hydrophobic AMCs is composed of micro/nanoscale hierarchical structures of synapses formed by unmelted particles and corrosion products. Several pores and pits were observed after chemical etching. As the chemical etching concentration and etching time increased, the solid−liquid contact fraction and surface energy of the hydrophobic AMCs first decreased and then increased. The water contact angle peaked at 142.52° when the coatings were chemically etched in 3 mol/L HCl solution for 60 min, thereby conforming to the Cassie−Baxter model. The passivation current density and pitting tendency of the hydrophobic AMCs in 3.5% NaCl solution were closely related to the chemical etching process. The prepared hydrophobic interface could form an effective air wall that isolates the coating surface from the corrosive medium and enhances its uniform corrosion resistance. However, chemical etching aggravated the pores and intensified the dissolution of inclusions, thereby increasing the pitting sensitivity of these concavities. The construction of robust and compact bionic hydrophobic interfaces is an effective approach to enhance the uniform corrosion resistance of AMCs.