Development of inorganic anticorrosive coatings for steel bars: Corrosion resistance testing and design

A densely structured three-dimensional geopolymer network could effectively impede the migration and diffusion of chloride ion. This study developed one kind of efficient and cost-effective and multi-component geopolymer coating (MGC) for inhibiting and delaying the corrosion of steel. The influence of alkali content, metakaolin replacement ratio, polyvinyl alcohol content, and titanium dioxide content on the fluidity, setting time, and rheological properties of MGC was investigated. Accelerated corrosion tests were carried out to determine the optimal formulation of MGC. The corrosion resistance of MGC prepared by different coating method was compared to commercial organic metal coatings, for which the salt spray test, adhesion test, and electrochemical impedance spectroscopy test were conducted. The results showed that the dip-coated specimen of MGC exhibited 63.8% decrease in mass loss, 59.5% decrease in adhesive strength loss, and 38.1% increase in impedance modulus compared to commercial organic metal coatings. Furthermore, the corrosion protection mechanism of MGC was elucidated by analyzing its microstructural characteristics including the functional groups formed on the surface of coated steel bars. In terms of cost, MGC reduced the total cost by about 15 times compared to commercial organic metal coatings.