Smart nanoarchitectonics of epoxy coating: Preparation, release behavior and self-healing performance based on mesoporous silica nano-containers loaded with DMTD inhibitors

Self-healing coatings doped by nano-containers loaded with inhibitors have shown remarkable anti-corrosion efficiency and durability in extending metal life and slowing down coating failure. However, low loading capacity of corrosion inhibitors in nano-containers is a problem plaguing the further development and application of smart coatings. In this study, mesoporous silica with large pore sizes (MSN) was synthesized using the soft template method which significantly increased the loading capacity of the corrosion inhibitor, and a smart self- healing composite coating was designed, which could protect carbon steel from corrosion and provide durable protection for it. Specifically, the composite coating (EP/DMTD@MSN-PAA) was prepared by incorporating mesoporous silica nano-containers embedded with 2,5-dimercapto-1,3,4-thiadiazole (DMTD) molecules into the epoxy resin coating. The results of BET test showed that the prepared MSNs had high specific surface area (734.97 m2/g) 2 /g) and large pore volume (0.85 cm3/g). 3 /g). The thermogravimetric (TG) analysis showed 35.7% of loading amount of corrosion inhibitors in the nano-materials. Response release experiments showed that the DMTD@MSN-PAA had of acid-response release characteristics. When pH value of the system decreased from 7 to 3, the release amount of the DMTD molecules increased from 40.3% to 93.7%. The contact angle test showed that the epoxy resin (EP) coating had a contact angle value of 57.7 degrees, degrees , while those of the composite coatings doped with 1 wt%, 3 wt% and 6 wt% DMTD@MSN-PAA (EP/DMTD@MSN-PAA) were 65.1 degrees, degrees , 75.2 degrees degrees and 67.2 degrees, degrees , respectively. These results indicated that the composite coatings had better hydrophobicity compared to the EP coating, and were conducive to prolonging the coating service time. The anti-corrosion performances of both the EP and the composite coatings with different doping amounts of DMTD@MSN-PAA were evaluated by EIS measurements. The R ct value of the EP coating decreased from 190.3 to 25.1 Omega & sdot; cm2 2 within the time of 48 h of immersion in 3.5 wt% NaCl solution, while ones of the EP/DMTD@MSN-PAA coatings doped with 1 wt%, 3 wt% and 6 wt% of DMTD@MSN-PAA increased from 303.1, 720.7.7, 523.4-1426.4, 2113.8, 1066.3 Omega & sdot; cm 2 , respectively. In addition, the corrosion resistance of the EP and composite coatings were further evaluated by etching experiments. The results showed that after 35 d of immersion, compared with that of the EP coating, surface corrosion degree of the composite coatings was lower, and the scaling off speed of the coatings slowed down, which further proved that the composite coating had strong corrosion resistance and special self-healing characteristics.