Protective Effect on Metal Substrate of Epoxy Resins Containing Corrosion Inhibitor Embedded into Suitable Nanocarriers

Abstract

The corrosion of metals is a serious technological problem and a variety of methods such as cathodic protection and insulating coatings has been developed to overcome it. However, the use of an active coating on metal substrates is proposed to be an innovative and effective approach. Although 2-mercaptobenzothiazole (MBT) is an efficient corrosion inhibitor for metals, its direct addition into the polymer coating or paintis not so much effective, because it is water-soluble, photodegradable and creates discontinuities in the coating layer, thus decreasingits barrier properties. A valuable approach to improve its anticorrosion performance is the entrapment of MBT into nanocarriers to be used as containers and reservoir. In the present work two different types of nanocarriers on the anticorrosion effect of 2-mercaptobenzothiazole molecule have been investigated. In particular, halloysite nanotubes (HNTs),in which MBT is loaded in the inner empty lumen through a vacuum procedure,and Zn–Al-layered double hydroxides (LDHs), in which MBT is intercalated through ionic-exchange, have been evaluated. Release tests of MBT from the obtained active particles in aqueous corrosive solution have been performed. Results have been correlated with the data obtained by visual inspection of anticorrosion effect of the active nanocarriers added into epoxy coatings and used to protect commercial steel substrate during accelerated corrosion tests.