Geopolymer-based Coating Material for Metal Substrate

Coating is an applied layer on the substrate to enhance properties of the substrate.
Geopolymer is produced through geopolymerization between alumina-silicate and
alkaline solutions and has a great potential to be utilized as geopolymer-based coating
material. The aim of this study is to investigate the properties of the geopolymer and
geopolymer coated steel using microwave incinerated rice husk ash (MIRRA) and fly
ash as the source of alumina and silica for the geopolymerization process.
Characterizations were used to characterize the raw materials and geopolymers such as
chemical composition and structure while geopolymerization was done by varying the
synthesis parameters such. as solid/liquid ratio and SiOz/ Al.J<l) ratio.
The results showed that the setting time of geopolymer decreased with increasing
solid/liquid ratio, while the highest compressive strength of 31.78MPa was obtained
when the solid/liquid ratio was 3.0 with 15% MIRRA addition. It was also observed that
the change in mass of geopolymer due to water absorption ranged from 0.002% to 0.018%
only. The results also showed that the coating thickness increased with increasing
solid!1iquid ratio while the adhesive strength increased with the reduction in solid/liquid
ratio as well as the addition of MIRHA where the highest adhesive strength which was
larger than iSMPa, was achieved at solid/liquid ratio and MiRHA addition of 2.0 and
15%, respectively. Moreover. the corrosion ievei of the geopoiymer coated steel
decreased with the addition of lvHRHA and increasing solid/liquid ralio. From this srudy,
lvHRHA could be a potential raw materiailo enhance the performance of geopolymer as
a coating malenal.