# Special Issue: Corrosion Effects and Smart Coatings of Corrosion Protection
###### Abstract  
Materials that are capable of adapting their properties dynamically to an external stimulus are called stimuli-responsive or \"smart materials\" [1]. The development of intelligent coatings (smart coatings) originates from the research of intelligent materials. Hence, smart coating is a coating which detects and responds dynamically to the changes in its environment in a functional and predictable manner [2]. Compared with traditional organic coatings, which have better corrosion and pollution resistance [3], there are now many types of intelligent coatings, such as coatings that are self-healing, self-reporting, antibacterial, and so on. [PERSON] et al. [4] mixed mesoporous polydopamine microspheres with aqueous epoxy resin and hydrophobic silica nanoparticles to prepare a self-healing intelligent antifouling coating. Under the stimulation of the external environment, the defects in the coating can be self-headed, and the superhydrophobic and antifouling properties of the coating can be restored. [PERSON] et al. [5] designed a stimulus-responsive mesoporous silica nano-container loaded with fluorescein isothiamate and added it to the epoxy coating. Through the change in the corrosion environment at the damaged part, the fluorescent probe molecules were stimulated to release fluorescence, so as to realize the self-report function of the coating. [PERSON] et al. [6] linked poly(2-disopropylaminoethyl methacrylate)-b-poly(2-methacryloxyethyl phosphate choline) (PDPA-b-PMPC) and poly lysine (plys) on tannic acid (TA) to prepare an intelligent antibacterial coating, which showed significant antibacterial activity and adsorption to proteins. On the basis of passive barrier, these coatings achieve active protection by responding to changes in the external environment and improve the service life of the coatings [7]. Many so-called smart coatings that do not respond to changes in a dynamic and reversible manner may actually be classified as very-high-performance and novel coatings. Smart coatings can be designed and prepared in many ways such as by incorporating stimuli-responsive materials such as light, pH, pressure, temperature, etc., sensitive molecules, nanoparticles, and antimicrobial agents as additives [8]. Loading the corrosion inhibitor and the healing agent into the micro-nano-container and realizing the release of their stimulus response in the coating are conducive to maintain their long-term reactivity and stability. [PERSON] et al. [9] synthesized microcapsules containing linseed oil and then added benzimidazole between microcapsules and pH-responsive polyelectrolyte Pei layer by layer self-assembly technology to prepare a new smart coating of stimulus responsive microcapsules and proved the anti-corrosion performance of epoxy coating containing microcapsules by electrochemical impedance spectroscopy (EIS). [PERSON] et al. [10] synthesized pH-responsive polyaniline hollow microspheres encapsulating corrosion inhibitor 2-Mercaptobenzothiazzole and combined them with aqueous epoxy resin to prepare intelligent coatings, which have excellent corrosion resistance and self-healing ability. [PERSON] et al. [11] successfully prepared environmentally friendly pH-sensitive mesoporous chitosan microspheres by W/O lotion chemical crosslinking method and added them to polyacrylate coating. The self-healing performance of the coating is improved, and the furtherexpansion of corrosion is prevented due to the release of corrosion inhibitors. According to the electrochemical impedance spectrum, the release rate of the inhibitor is the fastest at pH = 9. [PERSON] et al. [12] modified mesoporous silica by 2-Diethylaminoethyl methacrylate (DEAEMA) and loaded the corrosion inhibitor benzotriazole (BTA) in the nanocontainer to prepare pH responsive nanocontainers. The pH-responsive epoxy composite coating was obtained by adding the nanocontainers to the epoxy coating. [PERSON] et al.