Bio-inspired (GO plus CNTs)-PU hydrophobic coating via replication of Lotus leaf and its enhanced mechanical and anti-corrosion properties

In this paper, a novel kind of hydrophobic waterborne polyurethane (PU) composite coating is introduced via a two-step process, i.e., the graphene oxide (GO) + carbon nanotubes (CNTs) hybrids as synergistical reinforcement, and nano-casting the surface with fresh lotus leave. The experimental results reveal that: 1) Comparing with pure PU coating, the composite coating showed enhanced mechanical properties due to effect of the GO + CNTs hybrid, i.e., tensile strength were increased from 19.28 to 26.77 MPa, hardness and maximum load were increased by 60% and 100% respectively. 2) The composite coating surface exhibited an increased contact angle from 70 degrees to 121 degrees, due to the nano/micro convex structure duplicated by lotus leaf. 3) The composite coating showed a great improvement of corrosion resistance, i.e., the inhibition efficiency could maintain 98.35% after immersing in 3.5% NaCl solution for 20 days. The present work provides a simple and environment-friendly process to prepare a hydrophobic composite PU coating without any organic solvents, toxic chemicals and surfactants, which is expected to be widely used in sever corrosion prevention areas, such as marine engineering and construction industry.