Corrosion rate evaluation by gravimetric and electrochemical techniques applied to the metallic reinforcing structures of a historic building

•Emphasis on steel maintenance being required for successful restoration of historical buildings.•Discussion of the tests and procedures to determine the influence of neighbourhood on the corrosion of metallic reinforcing structures.•Shows the importance of understanding in detail what happens at the metal surface in contact with contaminant agents through to electrochemical techniques. This work presents the diagnosis procedure followed to determine the degree of damage of a 100-year-old reinforced concrete building located in Barcelona city, the Sant-Manuel pavilion at Hôpital de la Santa Creu i Sant-Pau. Some structural components of this building were affected by severe corrosion problems in the reinforcing steel UPN profiles. In order to obtain a representative sample set, a preliminary inspection of the macroscopic architectonic structure was applied at selected zones that exhibited the metallic backbone. Gravimetric and electrochemical techniques have demonstrated that some UPN profiles presented high corrosion rate. This was mainly due to the presence of water pipes installed beside the metallic structure, which was a source of humidity, and also to the presence of calcium carbonate, calcium silicate hydrate, and calcium chloride substances inside the cement in direct contact with the metallic structures, which were responsible for the steel depassivation. The work shows a practical example of how a suitable combination of chemical, physical and electrochemical techniques can be applied together to characterize a corrosion process, the obtained results validating and corroborating the prediction of the corrosion rate in metallic structures.