A facile method for constructing a superhydrophobic zinc coating on a steel surface with anti-corrosion and drag-reduction properties

Highlights: • A geopolymer based zinc coating with micro rough structure was prepared by sand particles. • Nano silicon filaments can in situ grow on geopolymer to form a superhydrophobic surface. • Geopolymer as binder enhance the anti-abrasion and durability of the coating. • Superhydrophobic zinc coating can be readily applied for steel. • The prepared coating possesses drag reduction, corrosion protection and repairable ability. Superhydrophobic surfaces are expected to be an effective technology for protecting marine metals. However, most of the reported methods are difficult to apply on steel surfaces. Herein, this study proposes a facile method of constructing a composite coating consisting of a zinc coating and superhydrophobic surface on a steel surface. A geopolymer-based zinc coating was precoated on the steel surface, and sand particles were used to form a rough micro structure. Then, the inherent alkaline species existing in the pore solution of the geopolymer trigger the hydrolysis-polymerization reaction of poly(methylhydrogen)siloxane (PMHS). After thermal curing, a superhydrophobic interface with a hierarchical micro/nanostructure can be assembled in situ on the coating surface. The prepared mechanism of the coating was characterized by SEM/EDS, XRD, CLSM, XPS, and the superhydropohocity performances were tested by water contact angle, drag reduction measurement and electrochemical analysis. The results show that the designed steel coating displayed a 45% drag reduction rate, 98% superhydrophobic repairable ability and excellent corrosion protection.