Micro/nanocapsules for anticorrosion coatings

Abstract

In the last decade, the interest in the self-healing and slow release coatings applied against corrosion increased dramatically as it helps to expand duration of coating and, at the same time, to increase the structural materials' life. In these types of paints are micro and nanoncapsules that enable the reparation of the coating upon exposure to external stimuli like mechanical degradation, changes in the pH and/or temperature. In spite of the extensive laboratory research work, there are many unsolved problems in understanding the function of smart coatings. To summarize the knowledge accumulated up-to-now in this topic will help both academic and industrial specialists to keep in center of interest for further research to solve problems that will result in development of more effective micro-and nanocontainers for different paints. Coatings with micro-and nano-containers/capsules improve the basic coating characteristics like anticorrosion efficiency. The chapter first discusses the importance of self-healing and slow release phenomena, and then it focuses on the basic knowledge of micro-and nano-capsule preparation techniques as well as on the importance of "filled" capsules. Advances on preparation of different types of the containers (organic, inorganic, and multilayer) are reviewed. Then the shell and wall materials, the wall thickness and its mechanical properties is discussed as one of the most important questions. One must keep in mind that the capsules must remain intact for years during storage, coating formulation and application and, additionally, in the dry coating.Experimental techniques used for characterization of micro/nanocapsules (size, size distribution, mechanical stability etc.) are discussed. Corrosion is a serious problem all over the world. The cost of corrosion includes materials for reparation of corrosion damage, the reduced capacity of equipment and the manpower to repair it increases. The corrosion problems could be solved by protective layers that ensure the integrity of the metal. However, even the best protective coatings can allow the diffusion of oxygen, the admittance of aggressive chemicals and moisture to the metal surface; the coating could delaminate from the solid surface and, as a consequence, the dissolution of metal starts. The first signs of the corrosive attack are cracks and pits formed on the solid surface. The problem could be solved or mitigated by coatings that are tailored for protection against corrosion and any other undesired external interaction. They ensure a long-term performance of solids.There are great varieties of protective coatings (metallic, inorganic, organic) which are used to protect the surface damages caused by corrosive environment.Anticorrosion coatings could be classified according to their activity, like sacrifice and barrier coatings. In the case of sacrificial coatings, an additional metal layer corrodes instead of the base metal. The barrier films should be non-porous; this is how they save the metal from corrosion.Polymers ca...

The interaction of atoms and molecules with nanocapsules and hollow nanowires

“…The ability of nanocapsule to retain helium, as well as other substances, such as drugs 9 , 10 , can be used for transportation and storage. Moreover, nano- and micro-capsules are embedded in the material matrix as an anticorrosion coating 35 , providing a recovery process 16 for materials that can partially or completely repair damage, such as cracks.…”

Nanocomposite Coatings for Anti-Corrosion Properties of Metallic Substrates

“…The encapsulation procedure must take into consideration the chemical nature of the reactive healing agent to avoid the diffusion of the liquid compound captured inside and out of the capsule shell during storage. At the same time, the microcapsule walls must be sufficiently resistant to processing conditions during their incorporation into the matrix of the host composite [107].…”

Electrospraying of Bio-Based Chitosan Microcapsules Using Novel Mixed Cross-Linker: Experimental and Response Surface Methodology Optimization

“…For instance, the self-healing performance in the anticorrosion application is influenced by the size and content of the capsule. By establishing a relationship between microcapsule size and microcapsule weight fractions, it was possible to develop self-healing systems that repaired specific types of corrosion damage [ 21 ]. Size affects the toughness of microcapsules and the interface between them and the coating matrix in which they are incorporated.…”

“…To obtain spherical capsules, sufficient polymer entanglements must be present [ 4 ]. Sphericity was a crucial requirement in self-healing applications where sphericity improved properties such as mechanical stability and strength of the microcapsules [ 21 , 26 ]. Spherical microcapsules also provided smoother surfaces [ 21 , 25 ].…”

“…Sphericity was a crucial requirement in self-healing applications where sphericity improved properties such as mechanical stability and strength of the microcapsules [ 21 , 26 ]. Spherical microcapsules also provided smoother surfaces [ 21 , 25 ]. Generally, the size, sphericity, and yield of microcapsules generated by electrospraying may be influenced by process parameters such as voltage, needle size, flow rate, and TTC distance, along with solution parameters.…”