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A new approach was adopted to improve the corrosion behavior of the chromium nitride (CrNx) hard coating through magnetron sputtering deposition at different nitrogen flow rates. The influence of the nitrogen flow rates on the chemical composition, microstructure, mechanical property and corrosion behavior in artificial seawater of the CrNx coatings was investigated. The results show that with the increase of the nitrogen flow rates, the growth structure of the coatings varied from dense granular growth to coarse columnar growth. Increasing the nitrogen flow rates was helpful to decrease the Cr/N ratio and induce the phase transforming from mixed hexagonal Cr2N and face-centered cubic CrN to single CrN. However, the coatings under different nitrogen flow rates significantly improved the corrosion resistance and hardness of the steel substrate. Furthermore, at high nitrogen flow rate, the coating had high corrosion velocity and low protective capability against the substrate corrosion due to the fast corrosion channels acted by the columnar grain boundaries. While at the middle nitrogen flow rate, the coating with CrN phase, densely granular growth structure and moderate grain size resulted in excellent corrosion resistance and highest hardness. [ABSTRACT FROM AUTHOR]

Superhydrophobic coatings often face challenges related to poor friction and corrosion resistance. In this study, composite coatings were developed, featuring a top layer of SiO 2 nanoparticles and a bottom layer of epoxy resin (EP) and polydimethylsiloxane (PDMS). As the number of SiO 2 nanoparticles layers increased, surface roughness escalated, and the coating structure transitioned from SiO 2 nanoparticles entirely encapsulated by EP and PDMS to a small fraction of SiO 2 exposed on the coating surface. Leveraging the rough surface and low-free-energy properties endowed by Si-(CH 3) 2 and Si-O-Si hydrophobic groups, coatings comprising 3–5 layers SiO 2 nanoparticles exhibited superhydrophobicity and self-cleaning capabilities. These coatings retained their superhydrophobic properties even after enduring heavy friction from sandpaper, and demonstrated robust corrosion resistance over extended periods. Increasing the number of SiO 2 layers not only enhanced superhydrophobicity, corrosion and friction resistance, but also improved the coating-substrate adhesion. The designed coating structure exhibited superior corrosion resistance and coating-substrate adhesion compared to those of EP/PDMS + SiO 2 double-layer and EP + PDMS + SiO 2 mixed coatings. Moreover, the coatings displayed a self-healing ability, regaining superhydrophobicity following O 2 or Ar etching, facilitated by the upward movement of hydrophobic groups/bonds and intensity recovery. Coatings subjected to Ar etching exhibited better self-healing properties due to higher Si-O-Si and lower C-C/C-H bond intensities. This research presents novel insights for the practical application of superhydrophobic coatings. • Coating structure with all or a part of SiO 2 surrounded by EP and PDMS was designed. • Rough surface with low surface energy led to coating superhydrophobic and self-clean. • Improving SiO 2 layers number achieved good adhesion, corrosion and friction durability. • Coatings present better corrosion durability and adhesion than other structure design. • Hydrophobic groups floating up and intensity recovery were coating self-heal reason. [ABSTRACT FROM AUTHOR]