scholarly journals Electrochemical Study of Clean and Pre-Corroded Reinforcements Embedded in Mortar Samples with Variable Amounts of Chloride Ions

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 6883
Author(s):  
María de las Nieves González ◽  
María Isabel Prieto ◽  
Alfonso Cobo ◽  
Fernando Israel Olmedo
Keyword(s):  
Corrosion Potential ◽  
Cement Mortar ◽  
Electrochemical Techniques ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Corrosion Products ◽  
The Other ◽  
Steel Bars ◽  
One Year ◽  
Corrosion Of Steel

The present study investigates the possibility of re-surfacing previously corroded reinforcements and the suitability of the two electrochemical techniques that are widely used to determine the state of corrosion of steel (the corrosion potential Ecorr and the corrosion rate icorr). In order to test this, 32 pre-corroded B500SD reinforcing steel bars have been used for one year, where half of the bars have been cleaned to eliminate corrosion products. The other half have been maintained with the generated corrosion products. Subsequently, the bars have been embedded in cement mortar samples with variable amounts of chloride ion, and Ecorr and icorr have been measured for 250 days. The results showed that it is not possible to rework the reinforcement without removing corrosion products and that it is not possible to predict the passive or active state of steel by measuring Ecorr only.

Transport of Water and Chloride Ion in Cement Composites Modified with Graphene Nanoplatelet

2014 ◽  
Vol 629-630 ◽  
pp. 162-167 ◽  
Author(s):  
Hong Jian Du ◽  
Sze Dai Pang
Keyword(s):  
Chloride Ion ◽  
Chloride Ions ◽  
Chloride Diffusion ◽  
Cement Composites ◽  
Chloride Diffusion Coefficient ◽  
Barrier Effect ◽  
Graphene Nanoplatelet ◽  
Chloride Migration ◽  
Corrosion Of Steel ◽  
And Diffusion

Cement composites are vulnerable to harsh environments in which the chloride ions can ingress into concrete and thus cause corrosion of steel. In this study, the barrier effect of adding 2-D nanoparticles on the transport properties of cement-based materials was investigated. Graphene nanoplatelet (GNP), which comprises of a few layers of graphene stacked together, is chosen as a candidate in this study due to its impermeability and also its electrical conductivity which can be exploited for self-sensing functionality. Due to the large aspect ratio of the GNP, it is expected that the dispersion of these 2-D nanobarriers can contribute to the reduced permeability and diffusion of harmful agents. Experiments were carried out on cement mortar with 0%, 2.5%, 5.0% and 7.5% of GNP by weight of cement. The water penetration depth, chloride diffusion coefficient and chloride migration coefficient were reduced by 64%, 70% and 31% respectively with the addition of as little as 2.5% of GNP. This reduction can be attributed to the barrier effect of GNP which increases the tortuosity against water and chloride ions penetration, and also the refinement of the capillary pores which was revealed from the MIP tests. At GNP content exceeding 5%, the nanoparticles agglomerate, causing weak pockets which compromises the benefits of adding GNP to impede the ingress of fluids.

scholarly journals Chemical Composition of Corrosion Products of Rebar Caused by Carbonation and Chloride

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Jundi Geng ◽  
Junzhe Liu ◽  
Jiali Yan ◽  
Mingfang Ba ◽  
Zhimin He ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Corrosion Products ◽  
Chloride Salt ◽  
Oxide Content ◽  
Passivation Film ◽  
Steel Bar ◽  
Steel Bars ◽  
Main Components ◽  
Corrosion Of Steel ◽  
Peak Value

The microstructures of steel bars were studied by X-ray photoelectron spectroscopy (XPS), and the mechanism of corrosion of steel bars under the corrosion factors was elucidated. The results show that the passivation film and corrosive surface of the steel surface in the solution of the chloride-containing salt were coarser and the surface state was denser. The main corrosion products are FeOOH and FeO. The surface of the steel immersed in the simulated carbonized solution had loose pores. The main components are FeOOH, Fe3O4, and Fe2O3. The surface of the steel bar has a large amount of yellowish brown corrosion products in the simulated carbonization and chloride salt. The surface of the corrosion products was stripped and the main components are FeOOH, Fe3O4, and FeCl3, where the content of FeOOH is as high as 60%. The peak value of iron is gradually increased from the simulated chloride salt solution to the carbonized solution to the combined effect of carbonation and chloride salt; the iron oxide content is increased and corrosion of steel is obviously serious.

scholarly journals Effect of Chlorides on Conductivity and Dielectric Constant in Hardened Cement Mortar: NDT for Durability Evaluation

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Sunkook Kim ◽  
Joowon Kang ◽  
Sang-Hyo Lee ◽  
Yong Han Ahn
Keyword(s):  
Dielectric Constant ◽  
Pore Formation ◽  
Cement Mortar ◽  
Steel Corrosion ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Hardened Cement ◽  
Frequency Range ◽  
Nondestructive Technique ◽  
Normal Frequency

Dielectric constant and conductivity, the so-called EM properties (electromagnetic), are widely adopted for NDT (Nondestructive Technique) in order to detect damage or evaluate performance of concrete without damage to existing RC (reinforced concrete). Among deteriorating agents, chloride ion is considered as one of the most critical threats due to rapid penetration and direct effect on steel corrosion. In the work, cement mortar samples with 3 w/c (water-to-cement) ratios and 4 levels of chloride addition are considered. Conductivity and dielectric constant are measured in the normal frequency range. They increase with strength of mortar and more chloride ions due to denser pore formation. Furthermore, the behaviors of measured EM property are investigated with carbonation velocity and strength, which shows an attempt of application to durability evaluation through EM measurement.

Corrosion behavior of carbon steel in H2S-CO2-H2O-methyldiethanolamine (MDEA) solution under the presence of chloride ions

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Guiyang Wu ◽  
Xikui Gu ◽  
Wanwei Zhao ◽  
Rui Fan ◽  
Ting Mao
Keyword(s):  
High Temperature ◽  
Carbon Steel ◽  
Low Temperature ◽  
Corrosion Rate ◽  
Corrosion Behavior ◽  
Electrochemical Impedance ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Corrosion Products ◽  
Content Type

Purpose This paper aims to study the effect of chloride ions concentration on the corrosion behavior of carbon steel in methyldiethanolamine (MDEA) aqueous solution in the sight of different process parameters of purification plant. Design/methodology/approach Due to the decrease of filtration efficiency and separation efficiency, the chloride ion in the desulfurization solution is enriched. The corrosion behavior of carbon steel under chloride ion enrichment environment was studied by weight-loss method, electrochemical impedance spectroscopy, cyclic polarization curve, X-ray photoelectron spectroscopy and scanning electron microscopy. Findings The results show that temperature and hydrogen sulfide loads are the main factors of corrosion in CO2-MDEA-H2O-H2S environment. The enrichment of chloride ions reduces the corrosion rate at low temperature but promotes the corrosion rate at high temperature. The chloride concentration should be controlled below 3000 mg/L, and no pitting corrosion was found under the experimental conditions. Originality/value The effect of chloride ion enrichment on MDEA solution corrosion shows that at low temperature, the increase of chloride ion will reduce the acid gas load and increase the density of corrosion products, so as to reduce the corrosion; on the contrary, at high temperature, the density of corrosion products will decrease and the corrosion will be intensified as well. It is believed that the chloride ion should be controlled below 3000 mg/L according to the results of the tests.

scholarly journals Effects of Transverse Crack on Chloride Ions Diffusion and Steel Bars Corrosion Behavior in Concrete under Electric Acceleration

Materials ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2481 ◽  
Author(s):  
Fengyin Du ◽  
Zuquan Jin ◽  
Chuansheng Xiong ◽  
Yong Yu ◽  
Junfeng Fan
Keyword(s):  
Transmission Coefficient ◽  
Corrosion Behavior ◽  
Crack Width ◽  
Steel Corrosion ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Chloride Diffusion ◽  
Transverse Cracks ◽  
Steel Bars ◽  
Ion Transmission

Cracks greatly impact the durability of concrete structures due to their influence on the migration of chloride ions and the corrosion process of steel bars. This study investigates the effects of transverse cracks on chloride diffusion and the corrosion behavior of two types of steel bars (low carbon steel and corrosion resistant steel) in fly ash concrete with 1 kg/m3 solution-polymerized super absorbent polymer. Electrochemical impedance spectroscopy was used to monitor the chloride-induced corrosion behavior of steel bars in concrete. The chloride profile around cracks was tested via chemical titration. The corrosion products diffusion area was photographed and measured to evaluate the influences of cracks on the corrosion degree of steel bars. Transverse cracks greatly influence the chloride ion transport. When their width is less than 0.15 mm, cracks exert little influence on both chloride diffusion and steel corrosion. When the crack width exceeds 0.15 mm, the chloride ion transmission coefficient is significantly improved and steel corrosion is accelerated. However, when the crack width exceeds 0.20 mm, this effect is gradually weakened. Based on the experimental data, a quantitative relationship between the crack width and the chloride ion transmission coefficient in electric acceleration was established.

Chloride Ion Diffusion of Phosphoaluminate Cement Concrete

2009 ◽  
Vol 79-82 ◽  
pp. 99-102 ◽  
Author(s):  
Zhu Ding ◽  
Feng Xing ◽  
Ming Zhang ◽  
Peng Liu
Keyword(s):  
Portland Cement ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Hydration Products ◽  
Portland Cement Concrete ◽  
Ion Diffusion ◽  
Cement Concrete ◽  
Dense Microstructure ◽  
Corrosion Of Steel ◽  
Chloride Ion Diffusion

Penetration and diffusion of chloride ions in concrete can lead to the corrosion of steel bar and shorten the service life of concrete structures. Phosphoaluminate cement (PAC) is a new cementitious material which has many special properties compared to Portland cement (PC). In the study, chloride ion diffusion in PAC concrete was tested with RCM method. The phase composition and morphology of hydration products, pore volume of hardened paste cured for 28d were analyzed with X-ray diffraction (XRD) and mercury intrusion porosimetry (MIP). The results show that chloride ion diffusion coefficient of PAC concrete is much lower than that of Portland cement concrete under the same test conditions. The hydration products of PAC are main micro-crystalline phase and gel of phosphate and/or phophoaluminate, which formed a dense microstructure. There is no calcium hydroxide produced in the PAC hydration system. In hardened PAC paste, chloride ions might replace the atom group [OH] - and [PO4]3- of hydrates and become stable compounds. The resistance to chloride ion diffusion of PAC concrete will increase with the hydration age, because its microstructure becomes denser with the hydration age increasing.

scholarly journals Quantitative Non-Linear Effect of High Ambient Temperature on Chloride Threshold Value for Steel Reinforcement Corrosion in Concrete under Extreme Boundary Conditions

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7595
Author(s):  
Abdulrahman M. Alhozaimy ◽  
Mshtaq Ahmed ◽  
Raja Rizwan Hussain ◽  
Abdulaziz Al-Negheimish
Keyword(s):  
Corrosion Rate ◽  
Corrosion Potential ◽  
Electrochemical Techniques ◽  
Chloride Content ◽  
Threshold Value ◽  
Chloride Ions ◽  
Water Soluble ◽  
Linear Effect ◽  
Chloride Threshold ◽  
Exposure Temperature

This paper investigates the effect of high ambient temperatures on the chloride threshold value for reinforced concrete (RC) structures. Two commonly available carbon steel rebars were investigated under four different exposure temperatures (20 °C (68 °F), 35 °C (95 °F), 50 °C (122 °F), and 65 °C (149 °C)) using environmental chambers at a constant relative humidity of 80%. For each temperature, six different levels of added chloride ions (0.00%, 0.15%, 0.30%, 0.60%, 0.90%, and 1.20% by weight of cement) were used to study the chloride threshold value. Corrosion initiation was detected by monitoring the corrosion potential and corrosion rate using electrochemical techniques. The water-soluble (free) and acid-soluble (total) chlorides were determined using potentiometric titration according to the relevant ASTM standards. The threshold chloride content for each exposure temperature was determined by analyzing the corrosion potential, corrosion rate, and chloride content of each specimen. The results showed that the chloride threshold values were significantly temperature-dependent. At temperatures of 20 °C (68 °F) and 35 °C (95 °F), the chloride threshold value (expressed as free chlorides) was approximately 0.95% by weight of cement. However, as the temperature increased to 50 °C (122 °F), the chloride threshold decreased significantly to approximately 0.70% by weight of cement. The reduction in the chloride threshold value became more dramatic at an exposure temperature of 65 °C (149 °F), decreasing to approximately 0.25% by weight of cement. The trends were similar for the rebars from the two sources, indicating that the rebar source had little influence on the chloride threshold value.

scholarly journals Research on the Influence of Carbonation on the Content and State of Chloride Ions and the Following Corrosion Resistance of Steel Bars in Cement Paste

Coatings ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1071
Author(s):  
Hui Wang ◽  
Ailian Zhang ◽  
Linchun Zhang ◽  
Junzhe Liu ◽  
Yan Han ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Blast Furnace ◽  
Cement Paste ◽  
Blast Furnace Slag ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Slag Powder ◽  
Free Chloride ◽  
Steel Bars ◽  
Furnace Slag

In this paper, the changes of free chloride ion concentration and bound chloride concentration in cement paste with different total and proportion of mineral admixtures under carbonation were studied. Moreover, the following corrosion resistance of steel bars buried in cement paste under carbonation was researched by testing the electrical resistance and alternating current (AC) impedance spectroscopy of reinforced cement paste. Results indicated that fly ash and granulated blast furnace slag powder with the content less than 20% by mass ratio of total binder hindered the solidification of chloride ions in cement-based materials, and blast furnace slag powder with the content higher than 20% promoted the solidification of chloride ions in cement paste. The carbonation effect was able to decrease the amount of solidified chloride ion and increase the amount of free chloride ions leading to accelerating the corrosion of reinforcement. Meanwhile, the blast furnace slag powder with the content higher than 20% could effectively promote the corrosion resistance of steel bars.

scholarly journals Effects of the zinc and zinc-nickel alloys electroplating on the corrodibility of reinforced concrete rebars

2016 ◽  
Vol 9 (4) ◽  
pp. 595-605 ◽  
Author(s):  
F. A. CEDRIM ◽  
V. L. S. ALMEIDA ◽  
C. A. C. SOUZA ◽  
M. D. JESUS ◽  
D. V. RIBEIRO
Keyword(s):  
Reinforced Concrete ◽  
Nickel Alloys ◽  
Corrosion Potential ◽  
Salt Spray ◽  
Chloride Ions ◽  
Nacl Solution ◽  
Steel Bars ◽  
Quantitative Analyses ◽  
Electroplating Process ◽  
Zinc Nickel

Abstract This paper shows the analysis performed on the corrosion parameters of three groups of reinforcing steel bars, two of these coated by electroplating process with Zinc (Zn) and Zinc-Nickel (Zn-Ni), and the other without any coating. It was used reinforced concrete specimens, which ones were grouped and then subjected to two different corrosion accelerating methods: aging wetting/drying cycles and salt spray exposure. Corrosion potential was measured to qualitative monitoring of the process and, after the end of the tests, corrosion rate was estimated by measuring the mass loss, to quantitative analyses. As it was expected, coated bars presented a better performance than the average bars regarding the corrosion resistance in chloride ions containing environments. It was also observed that the drying/ NaCl solution wetting cycles seems to be more severe than salt spray fog apparatus with respect to the acceleration of corrosion process.

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