Stress Corrosion Resistance of Geopolymer Anticorrosive Coating in Chloride Saline Soil Environment
摘要
The bearing capacity and service life of anchor bars are significantly diminished in chloride saline soil environments due to the occurrence of stress corrosion cracking. In addition, the existing anticorrosive coating materials have problems such as insufficient stress corrosion resistance, complex process flow and poor environmental protection. To address these issues, this study developed a geopolymer anticorrosive coating that can improve the stress corrosion resistance of anchor bars. Through laboratory testing, in the geopolymer anticorrosive coating, the optimum content of sodium hydroxide was 8.97%, the optimum content of asphalt was 2.05%, the optimum mesh of metakaolin was 1250 mesh, and the optimum particle size of titanium dioxide was 5 nm. Analysis via SEM and EDS revealed that the geopolymer anticorrosive coating facilitated the formation of a dense, continuous, and stable passivation film, primarily composed of Fe2O3, on the steel bar surface. This passivation film, in conjunction with the geopolymer coating itself, establishes a dual protective barrier. This synergistic system effectively impedes the ingress and corrosive attack of chloride ions on the underlying steel substrate. After 240 h accelerated corrosion in 6 mc/% (Saline soil ratio) chloride saline soil corrosion solution, the yield and ultimate strengths of the geopolymer-anticorrosive-coated steel bar increased by 18.4% and 19.3%, respectively, compared to those coated with epoxy asphalt paint. This result demonstrates the superior efficacy of the geopolymer coating in inhibiting stress corrosion cracking of reinforcing steel. Consequently, these findings offer valuable insights for enhancing the corrosion protection of slope anchor rods.