Chloride and carbonation induced corrosion of AISI 2201 duplex stainless steel rebars embedded in ordinary Portland cement mortars

摘要

Reinforced concrete structures deterioration is mainly originated by the presence of aggressive species such chlorides and pH reduction due to carbonation processes. The degradation takes places by pitting corrosion or general corrosion when chloride ingress or carbonation respectively, originate the initial activation. Among the different corrosion protection techniques that are extensively used in the construction and building sector (corrosion inhibitors, coatings, sacrificial anodes and impressed current application), the usage of stainless steel (SS) reinforcements offers a guaranty in terms of the life-time in service of the structures regardless other palliative methods. On the other hand the main issue of the SS rebars is their cost because of the Ni stock market fluctuation. In this work, new low-nickel content duplex AISI 2001 SS embedding concrete has been probed to present good corrosion behaviour. The electrochemical studies have been carried out monitoring the Ecorr and Icorr of different chloride contaminated specimens within the range comprised between 0<[CI~-]<4%. The carbonation induced corrosion behaviour has been performed by immersion of the reinforced concrete specimens to carbonated pH=9 buffer solution. Electrochemical corrosion has been monitored over one year time by means LPR and EIS techniques. XPS analysis performed on the 2001 SS reinforcements after chloride contamination and carbonation process does not reveals any corrosion product formation. The passive film composition has been evaluated and compared with the austenitic AISI 304 SS and duplex 2304 SS. It has been found that duplex AISI 2001 SS remains in the passive state even in the presence of [Cl~-]=4% and pH=9, thus probing its suitability as concrete reinforcement.