# Special Issue: Corrosion Effects and Smart Coatings of Corrosion Protection
###### Abstract
[13] synthesized ZIF-8, which can explain the release of corrosion inhibitor in acidic water, by a microemulsion method, and studied the protective performance of different mass fractions of ZIF-8 on epoxy coating. The results show that the anti-corrosion performance of the modified epoxy coating is improved with the increase in the mass fraction of ZIF-8 filler. In addition, the author also pointed out that the excellent anti-corrosion performance of ZIF-8 coating may be attributed to two reasons. First, ZIF-8 as a nano filler can block the micropores generated during the preparation and curing of the coating and reduce the penetration path of corrosive electrolyte solution; secondly, the amine group in ZIF-8 reacts with the epoxy group, which not only increases the crosslinking density of the coating but also improves the dispersion of ZIF-8 in the coating. ZIF-7 has similar performance to ZIF-8, which can hydrolyze and release corrosion inhibitor under acidic conditions. [PERSON] et al. [14] studied the anti-corrosion performance of ZIF-7 and the influence of the content and size of ZIF-7 on the coating performance. The electrochemical impedance changes in the epoxy coating added with ZIF-7 and the blank epoxy coating in HCl solution were compared. The results showed that the epoxy coating added with ZIF-7 showed a good corrosion inhibition effect on the steel substrate in acidic medium. When the content of ZIF-7 was 1.7 wt.%, the corrosion resistance of the coating was the best. On the basis of [PERSON] et al., [PERSON] et al. [15] prepared BTA@ZIF-7 nanoparticles under acidic conditions. The inhibition efficiency of nanoparticles can be as high as 99.9%, and the release amount of corrosion inhibitor can reach 30 wt.% within 10 min, while the release amount of corrosion inhibitor is less than 4 wt.% under neutral conditions. Electrochemical impedance spectroscopy indicates that coatings containing BTA@ZIF-7 are impedance modulus at low frequency volumes up to 1.86 \(\times\) 10\({}^{5}\)\(\Omega\)-cm\({}^{2}\). In addition to the pH-responsive intelligent anti-corrosion coating, there are also temperature responsive intelligent anti-corrosion coatings. [PERSON] et al. [16] designed a new nano container composed of hollow silica inner wall and stimulus responsive polymer outer wall. When \(N\)-isopropylacrylamide is selected as the polymer, the nanocarrier responds to temperature, thus achieving the controllable release of benzotriazole (BTA), a corrosion inhibitor. Photoresponse self-healing coatings have the advantages of the instantaneous, remote, environmental protection, and accurate repair of damaged parts. [PERSON] et al. [17] used silica microspheres as templates to prepare hollow mesoporous silica microspheres and used azobenzene isomers to modify the inner wall of the mesoporous to obtain photoresponsive hollow mesoporous nanocarriers. The photoresponsive nanocarriers can release corrosion inhibitors under ultraviolet light and inhibit the diffusion of corrosion inhibitors under visible light, realizing the controllable release of photoresponsive corrosion inhibitors. Stimuli-responsive materials are combined with superhydrophobic materials and antifouling agents, which can achieve controllable release of antifouling agents. [PERSON] et al. [18] modified ZIF-8 nanoparticles with low-surface-energy materials 1H,1H,2H,2H-perfluorooctyltriethoxysilane and prepared a superhydrophobic coating with epoxy resin as binder. According to electrochemical impedance spectroscopy, it was found that at 3.5 wt.% after soaking in NaCl solution for 1 h, the charge transfer resistance of Q235 steel was increased by more than seven orders of magnitude, while the impedance modulus at low frequency decreased by less than one order of magnitude after soaking for 7 days. The excellent self-cleaning ability of the coating was proved by the dripping test and immersion test, which indicated the anti-corrosion performance of the superhydrophobic coating. [PERSON] et al.