Corrosion Resistance of Cr-bearing Rebar in Concrete with Chloride Ion Content

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Reinforced concrete structures made using Cr-bearing rebars subject to microcell corrosion were assumed with the aim of developing Cr-bearing rebars having the required corrosion resistance in microcell corrosion environments. Their service lives were then estimated for each type of corrosion environment based on a microcell corrosion rate model, and requirements for Cr-bearing rebars to achieve a service life of over 100 years were calculated. As a result, the service lives of concrete structures reinforced with Crbearing rebars were found to increase as the Cr content increased in all types of corrosion environments. Also, Cr-bearing rebars with Cr contents of not less than 11 % and not less than 7 % ensured service lives of over 100 years in harsh and moderate chloride attack zones, respectively. In carbonation zones, a Cr content of not less than 3 % was proven to provide corrosion resistance for over 100 years.

“…We examined their relationships based on research data in the literature, 13,16,20) as well as our past studies. 9,12) The results are shown in Fig. 3.…”

Section: Formulation Of Initial Corrosion Rate (V In )mentioning

confidence: 79%

Section: Formulation Of Diffusion/penetration Rates Ofmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Service Life Estimation of Reinforced Concrete Structures Made Using Cr-bearing Rebars in Microcell Corrosion Environments

Tae

Kyung

Ujiro³

et al. 2007

Self Cite

“…[9][10][11][12] With this as a background, the authors have been investigating the corrosion resistance of Cr-bearing rebars having lower alloying elements, such as chromium, nickel, and molybdenum, than general stainless steel to allow production by processes similar to those of normal steel. [13][14][15] In this study, the service life of concrete structures reinforced with Cr-bearing rebars was investigated in macrocell corrosion environments induced by cover concrete cracking as part of a study for the development of Cr-bearing rebars having corrosion resistance suitable for the corrosive environments to which reinforced concrete structures are to be constructed. Based on the estimated service life, the Cr content of Cr-bearing rebars to achieve a corrosion resistance for up to 100 years was also calculated.…”

Section: Introductionmentioning

confidence: 99%

Service Life Estimation of Concrete Structures Reinforced with Cr-bearing Rebars under Macrocell Corrosion Conditions Induced by Cracking in Cover Concrete

Tae

Kyung

Ujiro³

2007

Self Cite

Cracked concrete members reinforced with Cr-bearing rebars were assumed for the purpose of developing Cr-bearing rebars having the required corrosion resistance in macrocell corrosion environments induced by cracking in cover concrete. The service life of concrete structures reinforced with Cr-bearing rebars was then estimated based on a macrocell corrosion rate model, and their Cr content to achieve a service life of 100 years was calculated. As a result, the service life of concrete reinforced with Cr-bearing rebars was found to increase as their Cr content increased regardless of the corrosive environment type. The calculation also revealed that Cr contents of 16 % or more and 13 % or more would lead to a service life of over 100 years in harsh and moderate chloride attack zones, respectively. In a carbonation zone, the Cr content to achieve a service life of over 100 years was calculated to be 9 % or more.KEY WORDS: Cr-bearing rebar; service life estimation; macrocell corrosion; crack.ISIJ International, Vol. 47 (2007), No. 6, Study OverviewA concrete member reinforced with a Cr-bearing rebar having a single crack was assumed. The penetration rates of Cl Ϫ and CO 2 through the cracked and sound areas were determined to express the material nonuniformity between the cracked and sound areas in terms of the difference in the chloride concentration and carbonation/uncarbonation. Also, the rates of macrocell and microcell corrosion were calculated based on the equations for calculating the polarization resistance and half-cell potential of Cr-bearing rebars, as well as an equation for calculating the concrete resistance, using the corrosion factors as parameters. The amounts of macrocell and microcell corrosion calculated from these corrosion rates were added, and the time required for the sum to reach the threshold amount of rust causing a crack in cover concrete was calculated as the service life. The use of the sum of macrocell and microcell corrosion amounts is intended to incorporate the possibility of their coexistence in rebar under cracked cover concrete. The amount of rust that would cause cracking in cover concrete was adopted as the limit state of reinforced concrete structures. The macrocell corrosion rate was determined using a model consisting of electrical circuits in concrete. Also, the polarization resistance of anodic bars in various corrosive environments was determined and substituted into the Stern-Geary equation and Faraday's law to calculate the microcell corrosion rate. On the other hand, the Cr content of Cr-bearing rebars to meet the requirement for a service life of 100 years was calculated based on the service life of concrete members estimated by the above-mentioned process. Formulation of Diffusion/Penetration Rates of Corrosion FactorsMacrocell corrosion induced by cracking in cover concrete is caused by material nonuniformity resulting from the differences in the penetration rates of Cl Ϫ and CO 2 . For this reason, it is necessary first to determine the penetration rates of Cl Ϫ ...

“…In concrete, the alkaline pore solution passivates the metal surface so that it does not rust/corrode. 8) Due to the carbonation reaction, the pH of the concrete environment decreases with time 9) and the steel converts from the passive to the active state. Coastline structures are deteriorated drastically due to the corrosion of the embedded steel, in spite of the alkaline nature of the concrete environment.…”

Section: Introductionmentioning

confidence: 99%

Electroless Nickel Coating Kinetics on TMT Rebar Surface and Coating Characterisation

Manna

Bandyopadhyay

2010

The corrosion resistance Ni-P-Fe alloy coating was obtained on rebar surface by an electroless process using glycolic acid as a complexing agent. During dipping of the iron scale free rebar in electroless solution, Fe first dissolves and the surface is activated. Subsequently, Ni, P and Fe are co-deposited by an autocatalytic process. The coating was characterised using SEM, EDS and XRD techniques. The weight percentage of Ni, P and Fe in the coating showed a relationship with the coating time. The Tafel and salt spray tests were conducted to find out corrosion resistance performance of coated samples. Electrochemical behavior of the coated rebar in simulated concrete environment is influenced by the pH of the concrete pore solution and the P content in the coating. Corrosion potential and the corrosion rate of the coatings increased with the increase in P content in the coating and pH of the pore solution whereas the resistance against chloride attack increased with increase in P content in the coating. Coated rebars showed reduction in bond strength in the range of 8 to 14 % compared to the bare rebars. The maximum (ϳ14 %) drop in bond strength was observed for longer coating time. This can be attributed to the smoother coating surface. The coating obtained under longer coating time showed higher amount of P which contributed to maximum surface smoothness. However, this bond strength was much above the necessary strength requirement according to Indian standard specification.