Corrosion Behavior of Cr-Ni Alloyed Corrosion Resistant Rebar in Chloride Environment

The corrosion resistance of a Cr-Ni alloyed corrosion resistant rebar and an ordinary rebar HRB400 was investigated by accelerated corrosion testing (salt-spray, alternate immersion) and electrochemical measurement in chloride environment. The corrosion rust layers were analyzed by scanning electron microscopy (SEM), electron microprobe analysis (EMPA) and X-ray diffraction (XRD). The results show that the alloyed corrosion resistant rebar had superior corrosion resistance to Cl^- in alkaline and neutral NaCl solutions. The corrosion rates of the alloyed corrosion resistant rebar in salt-spray corrosion test and alternate immersion test were 19.4% and 12.3% of those of HRB400 rebar, respectively. The rust layer of HRB400 was thick and loose, its major components were Fe₃O₄, α-FeOOH and β-FeOOH. The rust layer of alloyed corrosion resistant rebar were thin and dense relatively, and its major components were Fe₃O₄, α-FeOOH, β-FeOOH, γ-FeOOH, CrOOH and α-Fe₂O₃. The structures and types of rust layers were changed by adding Cr, Ni alloy elements and the corrosion resistance of steel bar in chloride environment was greatly improved by the way of reducing the corrosion sensitivity as well as improving the corrosion potential.