Corrosion Behavior of Cr Micro-alloyed Corrosion-resistant Rebar in Neutral Cl⁻-containing Environment

Abstract

A new low-cost corrosion-resistant rebar (HRB400R) was designed and fabricated by Cr micro-alloying. The HRB400R rebar had uniform distribution of Cr element in ferrite grains. The corrosion behavior of the rebar in the neutral Cl⁻-containing environment was studied systematically, and the improved corrosion resistance of the HRB400R rebar was revealed. According to the corrosion-morphology observation and electrochemical monitoring during the constant immersion corrosion in the 3. 5 mass% NaCl solution, the HRB400R rebar presented alleviated corrosion damage, nobler E_corr, lower I_corr, and larger R_t values, and these phenomena were more remarkable in the initial corrosion period. The elevated electrode potential of the rebar, caused by the solid-solution of Cr micro-alloying in the ferrite grains, was the key to the corrosion-resistance improvement. The HRB400R rebar also presented much lower mass-loss rate in the salt spray corrosion test. Besides the elevated corrosion resistance of the matrix, the doping and enrichment of Cr element in the rust layer was another factor for the higher corrosion resistance, which retarded the penetration of aggressive medium through the rust layer.