Rhamnolipids as an eco-friendly corrosion inhibitor of rebars in simulated concrete pore solution: evaluation of conditioning and addition methods

The objective of this study was to evaluate the use of rhamnolipids (RLs) extracted from Pseudomonas aeruginosa as a possible eco-friendly inhibitor for the corrosion protection of rebars in concrete. Two application methods were tested: application of RLs as a coating on the steel (conditioning method) and addition of the RLs directly to the aggressive environment (addition method). Both methods were evaluated for their ability to protect steel in simulated concrete pore solution containing 0.5 M NaCl. The results highlight a delay in the initiation of local corrosion followed by a rapid propagation rate of corrosion for conditioning method. This evolution is in relation with the heterogeneity of the formed RLs layers. The addition method provides a different film formation and better protection against corrosion. Using a 1 g·L ${}^{-1}$ concentration, the inhibition effect was observed at least for 24 h of immersion.