The Potential of Fly Ash Based Geopolymer Coatings for Steel Corrosion Protection

Nowadays, researchers are trying to understand whether geopolymers have the potential to be used as a coating material, particularly for protecting metal from corrosion attack. This study aimed to evaluate the effectiveness of fly ash-based geopolymer coatings in protecting steel by immersing the coated samples in a 3.5 wt% NaCl solution for immersion periods of 1, 7, 14, and 28 days. The uncoated steel showed the NaCl color changed to yellowish and became darker with increasing immersion time, indicating severe corrosion on the uncoated steel after 28 days. Surprisingly, with 3mm geopolymer thickness coated on the steel, NaCl solution remain unchanged until 28 days immersion period. The corrosion rate exhibits a very gradual increase, with only 0.112 mm/year recorded after 28 days of immersion. No defects such as blistering, peeling, or cracking were observed on the coated steel. These results indicate that geopolymer holds considerable promise as a coating material, warranting further investigation for its potential applications in this area.