The nature of rusts and corrosion characteristics of low alloy and plain carbon steels in three kinds of concrete pore solution with salinity and different pH

Correlation of corrosion characteristics and nature of rusts on low alloy (LA) and plain carbon (PC) steels exposed in simulated concrete pore solution of different pH is studied. Rusts formed under wet/dry conditions are examined by Raman spectroscopy and X-ray diffraction. LA rust is more adherent compared to PC as confirmed by measurement of weight in gain and electrochemical studies. EIS results show improvement in protective properties of steels with passage of time. Both steels are found prone to pitting attack in chloride contaminated pore solution. Rebars embedded in concrete exhibit same trend as recorded in solution exposure tests.

► LAS rebars corrode 2–3 times slower than PCS in concrete pore solution and mortars.
► Raman and XRD studies show that goethite and maghemite phases of rusts formed on LAS.
► On PCS unstable phases of lepidocrocite and akaganite are formed.
► EIS confirms more stable rust on LAS than on PCS.
► A model is proposed to explain formation of passive film on surface of steels.