Effect of ZnO on properties of metakaolin-based geopolymer anticorrosive coating

Nowadays, geopolymer coatings have been studied a lot due to their green and sustainable properties, and they have a great potential to partially replace traditional coatings in terms of corrosion resistance and economy. In this study, metakaolin-based geopolymer coating was used as the control group, and anticorrosive coatings were prepared by adding different dosages (2–8 wt%) of ZnO fillers to study the effect of ZnO on physical properties and anticorrosion properties of metakaolin-based geopolymer anticorrosive coatings. The results showed that when the mass fraction of the zinc oxide was 8%, it had the optimum effect on physical performance. The water absorption was 12.4%, and the toughness was 3 mm. In addition, the anticorrosive properties of the coating were studied by sodium chloride (NaCl) solution immersion test, wet–dry cyclic test, salt spray test, and electrochemical test. In sodium chloride (NaCl) solution immersion, wet–dry cycle, and salt spray test, a reduction of 43.8%, 50.6%, and 74.2% in corrosion area ratio, respectively, were achieved with a coating of 8% ZnO filled as compared with pure geopolymer coatings. The results indicated that the addition of ZnO enhanced the anticorrosion performance of the coating. The macroscopic test results were verified by SEM. This study lays a foundation for the subsequent research and performance improvement of metakaolin-based geopolymer anticorrosive coatings.