Encapsulation of active agents (corrosion inhibitors, pH indicators) has been described as a promising approach to impart controlled release and limit detrimental interactions between the active agents and the coating matrix. Mesoporous silica nanocapsules (SiNC) are engineered materials widely used for encapsulation. One synthesis route reported in the literature for these materials is based on a one-step emulsification process (oil-in-water microemulsion), using hexadecyltrimethylammonium bromide (CTAB) as emulsifier of the microemulsion. However, CTAB is also a source of toxicity to marine species, thus its replacement by other surfactants has been suggested.
This work describes the synthesis of new silica nanocapsules loaded with corrosion inhibitor 2-mercaptobenzothiazol (MBT) by using a gemini surfactant as a potential replacement for CTAB. The obtained nanocapsules were characterized by scanning electron microscopy (SEM), dynamic light scattering (DLS) and BET for pore size and surface area analysis. All the parameters were compared with those for nanocapsules based on CTAB, as well as ecotoxicity in relevant marine species. Nanocapsules were characterized by electrochemical techniques for anticorrosion applications, showing that they can be a prospective, new generation of nanomaterials with lower toxicity.
One of the most common ways to protect metals from corrosion relies on the application of protective coatings. As a passive barrier, they prevent the contact between electrolytes and the metal structure. However, any mechanical damages, temperature or UV radiation may cause the coating's deterioration, which leads to loss of protection and consequently triggers corrosion processes.1 Imparting active protection functionality in protective coatings via direct addition of corrosion inhibitors, is a common way to overcome this issue. However, when added directly to the coating, very often inhibitors not only act on the metallic substrate but also interact with the coating matrix. That undesired interaction results in inhibitor deactivation, fast coating degradation and constant leaching of inhibitor to the environment.2 In this context, encapsulation of corrosion inhibitors in an inert nanomaterial, can ultimately avoid these problems. Nanocontainers with inhibitors can be dispersed in coating formulations and the active agent is released only when the coating is damaged.3
