# Chloride Resistance of Assembled Bridge Piers Reinforced with Epoxy-Coated Steel Bars
## 3 Results and Discussion  
### Self-Corrosion Potential (\(E_{corr}\))  
As shown in Figure 8, the open circuit potentials of all steel bars generally decrease with the increase in migration time (excluding power-off time), indicating an increasing risk of corrosion for the steel bars. The untreated epoxy-coated steel bars also exhibit self-corrosion potential curves similar to those of metals. This is because although the epoxy coatings on these steel bars were intact along their length, their ends were not sealed with epoxy resin, which was necessary to form an electrical circuit for polarization curve testing.  
The self-corrosion potential curve of the epoxy-coated steel bar subjected to scratching treatment in Joint 1 is significantly lower than the other three curves, indicating the highest probability of corrosion. This increased risk is due to the severe surface coating damage that occurs after the scratched treatment. According to measurements (see Figure 9), the  
Figure 8: Self-corrosion potential.  
Figure 7: Schematic diagram of drilling powder.  
damaged area ratio of the scratched steel bars is above 5%, while the damaged area ratios for knocked and bent steel bars range from 3% to 4%. As shown in Figure 3, after the scratching treatment, the bright steel bar substrate was exposed, indicating deeper and more thorough damage to the epoxy coating as compared to other treatments. The self-corrosion potential curves of the steel bars subjected to bending/knocking and those with untreated coating show little difference, indicating that in Joint 1, corrosion resistance remains relatively unaffected as long as the epoxy coating damage ratio does not surpass 5%. The self-corrosion potential of steel bars in Joint 2 is lower than that in Joint 1, and the trend of self-corrosion potential decreasing over time is more pronounced. Significant defects at the interface between the pier and the grouting layer in Joint 2, which allow chloride ions to penetrate the specimen along the joint interface at a faster rate and accelerate the degradation of the passive film on the steel bar surface, are responsible for this trend. According to ASTM standard C876-22b [21], when \(E_{\text{corr}}(\text{vs.SCE})<-276\) mV, the corrosion probability reaches 90%, and when \(E_{\text{corr}}(\text{vs.SCE})<-426\) mV, severe corrosion of the steel bar is occurred. Under these criteria, the steel bars treated with scratching in Joint 1 started to corrode around 10 days of electromigration, while the remaining steel bars did not have significant corrosion risk until the end of electromigration. In Joint 2, all steel bars with damaged coatings started to corrode after 21 days of electromigration, while the untreated steel bars experienced a sharp drop in self-corrosion potential after 49 days of electromigration and maintained at a lower level, indicating that chloride ions easily reached the steel bar surface through the grouting interface. Since the criteria in ASTM C876-22b [21] are based on steel bars without coatings on the surface, there are inevitably differences in the electrochemical properties of steel bars with damaged epoxy coatings. Therefore, it is necessary to incorporate additional indicators to comprehensively assess the corrosion condition of the steel bars.