Design of a smart protective coating with molybdate-loaded halloysite nanotubes towards corrosion protection in reinforced concrete

Abstract

Using protective coatings is widely acknowledged as an effective strategy for preventing the corrosion of reinforcing steel and improving the durability of reinforced concrete structures. Nevertheless, a common challenge faced by the traditional coatings lies in the significantly reduced corrosion resistance due to its damage and cracking during the service life. Accordingly, a smart protective coating with active anti-corrosion performance was successfully designed and synthesised in this study, including a PA-polyvinyl alcohol (PVA) pretreatment layer and the molybdate-loaded etched halloysite nanotube (EHNT@MO). The PA-PVA grafting solution could fix EHNT@MO on the steel surface due to its strong chelating ability, resulting in an increased thickness of the pretreatment layer (∼5 μm) and exceptional barrier properties. Moreover, the release of molybdate from EHNT enables the smart protective coating to actively repair corrosion pits, thereby exhibiting excellent anti-corrosion performance. As a newly developed smart protective coating, it is expected to confer multifunctional properties to reinforcing steel in cementitious materials when subjected to aggressive environments.