Study On Protective Coatings To Steel Rebars

Abstract

This paper investigates the performance of various types of protective coatings to steel rebars such as passivating, barrier cum passivating and metallic type of coatings. The performance of Inhibited and Sealed Cement Slurry Coating (passivating type), Cement Polymer Composite Coating (passivating cum barrier type) and Galvanized rebars (metallic coating) were studied. The tests such as Chemical resistance test, Impressed voltage test, Anodic polarization test, Bond strength to concrete test, Impact test and Coating flexibility tests were conducted as per IS and ASTM Standards. Chemical resistance test and Impressed voltage test conducted on coated specimens revealed that, Inhibited cement slurry coating and Cement polymer composite coating possesses the necessary corrosion resistance properties as per IS and ASTM. Although Galvanization offers excellent sacrificial protection to steel rebars in the tested mediums except 3M NaOH, the performance of galvanized rebar under accelerated corrosion condition is for a limited period. A durability factor of 30 was observed in Anodic Polarization test for Inhibited cement slurry coating and cement polymer composite coating. Pull out test conducted on coated rebars showed that all the coating systems possess the necessary bond strength as required by the Indian Standards. All the coating systems offered excellent Impact resistance properties. Based on Coating flexibility test, it was suggested that the Inhibited cement slurry coating has to be applied over rebars after cutting and bending operation is over.