Asuncion Bautista, researcher at the Department of Science and Engineering of Materials and Chemical Engineering UC3M, confirms the use of duplex stainless steel in construction to prevent corrosion. The interest lies in investigating these materials also present alternatives at the time of building, because if you use this type of steel “structures could hardly have corrosion problems, even in harsh environments,” said the professor, an author the study.

In most cases, the deterioration of reinforced concrete structures due to the penetration of chlorides, water or carbon dioxide from the atmosphere. This causes a change in pH and thus, corrosion of stainless steel structures and reducing the service life of concrete. This leads to another problem, the economic: “There is a very high percentage of GDP spent on solving the problems of corrosion and in 20-30% of cases, it would solve if we apply the research being done,” explains scientific.

The main limitation of this type of steel is related to its high cost. However, its use is not needed throughout the structure, but only at critical points such as corners, external areas, bridges or tidal zones, ie in places where there is most likely to corrosion problems. At first, the initial expenditure by using duplex steels increases between 5 and 15%, yet its use in construction minimize maintenance costs of buildings and make him a negligible expense. To Asuncion Bautista, “the use of duplex steels is in the long run, a wise investment in environments with high chlorides and high temperatures.

A typical example where you’re using the duplex steel is in the construction of mosques in Arab countries. These buildings are intended to last for centuries in a harsh environment like the Gulf. In addition, also presented as an alternative for the repair of buildings of historic interest and, thus, increase its durability over time.

Duplex stainless steels have a structure of two phases: austenite and ferrite. This composition has a better performance against corrosion and has superior mechanical properties when compared with typical stainless steels. In this study has been demonstrated by electrochemical techniques and surface analysis of passive-layer that prevents corrosion of these steels, is more protective. It was also found that the corrosion resistance of these steels in concrete is clearly superior to austenitic which has more experience as reinforcements for concrete structures.

The study, “Passivation of duplex stainless steels in solutions simulating chloride-contaminated concrete” has been published in the journal ‘Building Materials’ by a group of researchers from the Universidad Carlos III de Madrid, Universidad Autonoma de Madrid and the CNRS-UPMC (Paris).