The Influence Of Applied Load On The Corrosion Of Epoxy Coated Rebar

In this paper, the failure process of epoxy-coated rebars under different magnitudes of loads in simulated concrete pore solution with chloride ions was studied by electrochemical impedance spectrum technology. The methods including coating adhesion test and SEM were used to characterize the failure mechanism of the coating under loads. Meanwhile, two pretreatment methods on rebar were taken to improve the corrosion resistance of the epoxy-coated rebars.The main contents are listed as follows:1. The failure process of epoxy-coated rebars under applied load in simulated concrete pore solution with chloride ions was studied by EIS technology. The result showed that the coating resistance of the sample under load declined, and the water absorption increased obviously. The higher the load, the faster the failure of the sample was. The coating water absorption test result was consistent with that of EIS. The result of the coating adhesion test pointed out that the applied load made the coating adhesion decline, and the adhesion decreased more obviously under higher load. The SEM images of the tension zone of samples revealed that applied load caused the desorption of the coating, and leaded to the degradation of the coating protective performance.2. The electrochemical behavior of epoxy-coated rebars with silane pretreatmeat under applied load in simulated concrete pore solution with chloride ions was studied by EIS technology. The results indicated that the coating performance of the samples under load declined, the higher the load, the faster the coating protection performance of the samples declined. The coating adhesion test result showed that applied load leaded the drop of the coating adhesion. The comparsion of coating resistances of samples before and after silane pretreatment with immersion time revealed that silane pretreatment improved the corrosion resistance of the samples and extended failure time of the surface coating of the samples.The coating adhesion test pointed out that silane pretreatment increased the coating adhesion. Regarding related test results, silane membrane improved the corrosion resistance of the rebar substrate.3. The electrochemical behavior of epoxy-coated rebars with phosphating pretreatmeat under applied load in simulated concrete pore solution with chloride ions was studied by EIS technology. The test results showed that the coating performance of the samples under load declined, the higher the load, the faster the coating protection performance of the samples declined. The variation comparsion of coating resistances of samples before and after phosphating pretreatment revealed that phosphating pretreatment improved the corrosion resistance of the samples. the coating resistance of samples with phosphating pretreatment was much higher. The coating adhesion test pointed out that phosphating pretreatment increased the coating adhesion. The SEM test showed that the rough surface of the phosphating film improved the coating adhesion; the GuSO4 solution test and electrochemical tests revealed the phosphating film could protect the substrate.