Jie Wei

Corrosion Evolution of Reinforcing Steel in Concrete under Dry/Wet Cyclic Conditions Contaminated with Chloride

The corrosion evolution of rebar in concrete was monitored by electrochemical impedance spectroscopy (EIS) under dry/wet alternated accelerated corrosion test. Four stages with different dynamic characteristics were observed during the corrosion evolution. They were passive stage, local corrosion controlled by the charge transfer step, accelerated corrosion controlled by the mass transfer step, and constant rate corrosion controlled by the mass transfer step through a barrier layer. X-ray diffraction (XRD) analysis showed that the corrosion product of rebar in mortar was composed of alpha-FeOOH, gamma-FeOOH and Fe3O4. The corrosion mechanisms of all four stages were discussed and the corrosion reactions were proposed according to the corrosion product and corrosion evolution characteristics.

EIS study on corrosion evolution of chemical quenched rebar in concrete contaminated with chloride

Abstract The corrosion evolution of scaled rebar cooled by a chemical reagent FM in concrete immersed in 3·5%NaCl aqueous solution was studied by electrochemical impedance spectra and compared with bare rebar. The results show that the corrosion evolution process of FM cooled rebar consists of three stages during the immersion: the passive stage, the accelerated corrosion stage dominated through the charge transfer step and the steady corrosion stage dominated through the mass transfer step. The corrosion rate of FM cooled rebar reaches a steady rate (<0·7 μA cm−2) after 80 days. However, the corrosion rate of bare rebar always increases at all immersion times. After immersion for ∼1 year, the corrosion rate of bare rebar is nine times larger of that of FM cooled rebar. Therefore, the corrosion resistance of the rebar has been improved significantly by applying the FM cooling process.

The corrosion inhibition effect of phytic acid on 20SiMn steel in saturated Ca(OH)2 solution with 1 mol L−1 NaCl

ABSTRACT A wise strategy to hinder the degradation of the steel rebar in concrete is finding a corrosion inhibitor to resist pitting corrosion at passive state as well as the general dissolution at active dissolution state. In this paper, the corrosion inhibition effect of phytic acid (IP6) on 20SiMn steel was investigated in the simulated concrete solution with chlorides, Sat.Ca(OH)2+1 mol/L NaCl(pH=12.9), by electrochemical methods and surface analysis techniques. The results show that IP6 could prolong the incubation time of 20SiMn steel from passive to pitting corrosion and enhance the charge-transfer resistance to a certain extent with the inhibition efficiency of around 30~50%. This is ascribed to the preferential adsorption of IP6 over chloride ion on the passive film through PO4 functional groups, which lead to the formation of a compact chelation film.

Crevice Corrosion of Several Supper Stainless Steels in the Simulated LT-MED Environment

Susceptibility and morphological characteristics of crevice corrosion for SS316, SS904L, SS254sMo and SS2507 in the simulated low-temperature multi-effect distillation environment were investigated by cyclic polarization test, scanning electron microscope and laser microscope. The results show that the crevice corrosion resistance of four kinds of stainless steel is ranked as SS254sMo ≈ SS2507 > SS316 > SS904L. There are “cover” structures over the edge of active crevice corrosion regions of SS904L, SS254sMo and SS2507, but SS316 is an exception. Galvanic corrosion characteristics appeared in the crevice of duplex supper stainless steel SS2507.