The protection of offshore structures and more specifically of wind turbines from marine corrosion is crucial. In order to improve the operational efficiency and the overall lifetime, protection from this harsh environment is necessary. In this work, it is presented the formation of the polystyrene shell microcapsules using 3-octanoylthio-1-propyltriethoxysilane (NXT) as a corrosion inhibitor carrier that has self-healing properties when combined with a proper catalyst on the metallic substrates. Specifically, the synthesized inhibitor is applied on the Zn85/Al15 arc spray coating on S355 J2+AR metallic substrate. With different concentrations of the applied NXT inhibitor, the corrosion properties of the Zn85/Al15 coatings were measured using Electrochemical Impedance Spectroscopy (EIS), Open Circuit Potential (OCP), Polarization Curve (PC) and Linear Polarization Resistance (LPR). Our results revealed that out of all the used concentrations, 300 ppm provides best protection. Surface morphological characterization exhibits that the coating is porous and corrodes readily, as expected to provide sacrificial protection to the underlying steel, so additional paint layer is necessary to fill the pores and provide a barrier layer. Hence, this work highlights the importance and applications of NXT based corrosion inhibitor with self-healing properties for metal structures in challenging environments.
Offshore structures are subjected to harsh and challenging environments. The combined effect of UV radiation, seawater, temperature fluctuations and seaborne debris make this environment challenging for materials [1]. Therefore, installed structures such as wind turbines need extra corrosion protection for improved lifespan. The use of cathodic protection is the most common method [2] of mitigating the corrosion of offshore structures. However, in the splash and atmospheric zone, the cathodic protection systems are ineffective due to the lack of electrolytic contact (seawater) between the structure and the anode [3]. Therefore, the use of protective coatings becomes indispensable in the splash and atmospheric zone. The focus of this work is the conversion of commercially available conventional paint (epoxy) system to a novel autonomous external self-healing paint system by the addition of suitable encapsulated healing agents in the form of microcapsules. Dmitry G. Shchukin and Helmuth Möhwald has reported these new generation of coatings with improved efficiency [4]. The selection of the catalyst plays a crucial role, therefore, appropriate catalyst has been identified to polymerize and solidify the encapsulated corrosion inhibitor after the rupture of the microcapsules. The use of Zn coating for the protection of the steel structures exposed to corrosive environments is a well-known processing technique [5]. Here is reported a method to combine Zn alloy coating with the enriched paint layer to create a unique and novel self-healing system. Therefore, first part of the research is to optimize the concentrations of the corrosion inhibitor for the protection of Zn85/Al15 coating. These results are presented in this paper. The second part of this ongoing research is to prepare the microcapsules and load them with the corrosion inhibitor to mix with a marine paint and a catalyst for the application of the sacrificial layer. For any damage to the coated surface, the corrosion inhibitor will be released and the self-healing process (polymerization) will take place. Hence, the focus of this research is to develop a novel cost-effective two-layer system to prevent corrosion and related problems in the offshore sector.
