Optimal condition for fabricating mechanically durable superhydrophobic titanium surface by rapid breakdown anodization: Self cleaning and bouncing characteristics

In this paper, we describe a simple, cost effective, fast, scalable and sustainable method for fabrication of mechanically durable superhydrophobic (SHP) surface of titanium by a rapid breakdown anodization (RBA) followed by molten stearic acid (MSA) chemical modification. In this new approach, the preparation time is only a minute. Instead of stearic acid-ethanol solution, molten stearic acid is the post surface modification, which made the preparation process rapid and simple. The anodized samples showed islands of TiO2 microclusters with complex hierarchical structures with nano pores uniformly distributed in the passive TiO2 matrix. Laser Raman spectroscopy (LRS) analysis revealed the TiO2 microclusters are polycrystalline in nature. The applied voltage, anodization time, immersion time and MSA bath temperature are optimized to obtain a robust mechanically durable SHP surface. FESEM images showed that both anodization and immersion parameters have significant effect on the surface morphology of microclusters. A maximum water contact angle (WCA) of 167.8 degrees with a sliding angle of 6 degrees was obtained for a Ti sample anodized at 50 V for 10 min after molten stearic acid immersion at 125 degrees C for 30 min. The prolonged anodization for 10 min promoted microcluster growth in all dimensions to form a highly hierarchical micro-nanostructure. The prepared samples showed vertical micro plate-like crystals of stearic acid on the micro clusters, which enhanced the very high WCA. The FTIR results revealed multiple bonding modes of stearic acid with TiO2 microclusters through surface hydroxyl groups. The prepared super-hydrophobic samples showed excellent self-cleaning and abrasion resistance.

Automated summary

This paper presents a simple, cost-effective, fast, scalable, and sustainable method for fabricating mechanically durable superhydrophobic surfaces on titanium. By utilizing rapid breakdown anodization and molten stearic acid chemical modification, the preparation time is reduced to just one minute. The optimized process results in a highly hierarchical micro-nanostructure with excellent superhydrophobic properties and abrasion resistance.