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 Under-insulation corrosion as a factor in decreased service life of industrial pipelines

2020 ◽  
Vol 10 (2) ◽  
pp. 264-273
Author(s):  
Victor N. Sokov ◽  
◽  
Elena A. Shuvalova ◽  
Anatoliy S. Zemlyanko ◽  
◽  
...  
Keyword(s):  
Carbon Steel ◽  
Service Life ◽  
Corrosion Rate ◽  
Thermal Insulation ◽  
Pitting Corrosion ◽  
Chloride Content ◽  
Chloride Ions ◽  
Water Soluble ◽  
Insulation Material ◽  
Critical Depth

The effect of porosity type and residual number of water-soluble chloride ions of insulation material on the under-insulation corrosion rate in industrial pipelines is considered. For the research, standard test methods were used in accordance with current Russian and foreign regulatory and technical documentation. The dependences of the corrosion rate and the damage area of carbon steel on the structure (porosity) of the thermal insulation material (open, semi-closed, closed), the residual number of water-soluble chloride ions and water-repellent agent is established. The residual life of a carbon steel pipeline was calculated at a critical depth of pitting corrosion under a thermal insulation layer of various materials. The types of thermal insulation materials characterised with lowest under-insulation corrosion rate are determined. The maximum 0.29–0.41 mm/year corrosion rate of carbon steel under materials with open porosity was 0.53–1.8 times lower than under comparable materials with closed porosity. An increased corrosion rate is determined to be directly proportional to an increase in the number of chlorine anions in the structure of the material. The smallest area of steel surface corrosion damage is observed under materials with open porosity. Among the materials examined, the requirements of the current regulatory standards are met by materials of the stone wool group having a low chloride content and basalt super thin fibre. The longest remaining service life (11 years) of a carbon steel pipeline at hdef= 5.87 mm critical depth of pitting corrosion is obtained under a rock wool layer having a low chloride content.

scholarly journals Corrosion of Steel Rebars in Anoxic Environments. Part I: Electrochemical Measurements

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2491
Author(s):  
Elena Garcia ◽  
Julio Torres ◽  
Nuria Rebolledo ◽  
Raul Arrabal ◽  
Javier Sanchez
Keyword(s):  
Corrosion Rate ◽  
Electrochemical Impedance ◽  
Electrochemical Techniques ◽  
Chloride Content ◽  
Offshore Platforms ◽  
Anoxic Conditions ◽  
Current Limit ◽  
Anoxic Environments ◽  
Corrosion Of Steel ◽  
Steel Rebars

The number of reinforced concrete structures subject to anoxic conditions such as offshore platforms and geological storage facilities is growing steadily. This study explored the behaviour of embedded steel reinforcement corrosion under anoxic conditions in the presence of different chloride concentrations. Corrosion rate values were obtained by three electrochemical techniques: Linear polarization resistance, electrochemical impedance spectroscopy, and chronopotenciometry. The corrosion rate ceiling observed was 0.98 µA/cm2, irrespective of the chloride content in the concrete. By means of an Evans diagram, it was possible to estimate the value of the cathodic Tafel constant (bc) to be 180 mV dec−1, and the current limit yielded an ilim value of 0.98 µA/cm2. On the other hand, the corrosion potential would lie most likely in the −900 mVAg/AgCl to −1000 mVAg/AgCl range, whilst the bounds for the most probable corrosion rate were 0.61 µA/cm2 to 0.22 µA/cm2. The experiments conducted revealed clear evidence of corrosion-induced pitting that will be assessed in subsequent research.

Influencing Parameters Analysis of Chloride Threshold Value on Reinforcements Embedded in Concrete

2011 ◽  
Vol 250-253 ◽  
pp. 202-206 ◽  
Author(s):  
Wei Qun Cao ◽  
Xiao Mei Wan ◽  
Tie Jun Zhao
Keyword(s):  
Corrosion Potential ◽  
Threshold Value ◽  
Corrosion Current ◽  
Visual Observation ◽  
Cement Type ◽  
Surface Conditions ◽  
Chloride Threshold ◽  
Type C ◽  
Parameters Analysis ◽  
Definition Of

The chloride threshold to develop active corrosion of the reinforcing steel does not seem to be a unique value and it depends on several factors, such as concrete mix proportions, cement type, C3A content of cement, blended materials, water/cement ratio, temperature, relative humidity, steel surface conditions and source of chloride penetration among others. Numerous studies have been already devoted to the study of the chloride threshold value for depassivation of the steel embedded in concrete. One of the reasons found for the scatter is the large number of variables that influence the chloride amount for depassivation. The other reason is the lack of accordance for the definition of the chloride threshold itself, either on the determining parameters (visual observation, corrosion potential or corrosion current) or on the expression of the threshold (as[Cl-]/[OH-] ratio or by weight of cement or concrete). The present paper presents chloride thresholds expressed as total, free and [Cl-]/[OH-] ratio.

Corrosion Behavior of Steel Reinforcement in Simulated Concrete Pore Solutions with Various pH and Chloride Contents

2014 ◽  
Vol 629-630 ◽  
pp. 168-172
Author(s):  
Shao Heng Hsieh ◽  
Ran Huang ◽  
Mao Chieh Chi ◽  
Pokuei Liang
Keyword(s):  
Corrosion Rate ◽  
Corrosion Behavior ◽  
Pore Solution ◽  
Chloride Content ◽  
Chloride Ions ◽  
Test Results ◽  
Weight Loss Measurement ◽  
Half Cell ◽  
Cell Potential ◽  
Significant Factors

Corrosion of rebar in reinforced concrete is a major problem affecting the integrity and loading capacity of the structures. Usually concrete pore solution provides high alkaline environment to protect steel from corrosion. However, the ingress of chloride ions or carbon dioxide would reduce the alkalinity and destroy the stable oxide film which could accelerate the corrosion process of rebar. This study was aimed to evaluate the combined effect of pH and chloride contents on corrosion behavior of rebar using simulated concrete pore solutions. Weight-loss measurement were performed to obtain the corrosion rate. Meanwhile, explore the effect of carbonation and chloride contents to Half-cell potential value on mortar and concrete. Test results show that both pH and chloride content are significant factors influencing the corrosion behavior of rebar. Higher corrosion rate was found in the rebar immersed in the solutions with smaller pH and higher chloride content.

scholarly journals Corrosion potential: influence of moisture, water-cement ratio, chloride content and concrete cover

2017 ◽  
Vol 10 (4) ◽  
pp. 864-885 ◽  
Author(s):  
M. H. F. Medeiros ◽  
F. C. Rocha ◽  
R. A. Medeiros-JUNIOR ◽  
P. Helene
Keyword(s):  
Corrosion Potential ◽  
Statistical Significance ◽  
Chloride Content ◽  
Concrete Cover ◽  
Chloride Ions ◽  
Degree Of Contamination ◽  
Destructive Testing ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Cover Thickness

ABSTRACT The method of measuring the corrosion potential is used as an electrochemical tool for helping the monitoring of the corrosion of reinforcements of concrete structures. As a criterion for evaluating results it is common to use intervals of corrosion potential and their correlation with corrosion probability, as precognizes ASTM C 876:2015. With this criterion, it is possible to establish an overview of the thermodynamic situation of corrosion in the structure or in the test specimen in laboratory. However, the method is influenced by several factors related with the concrete, the environment and with procedures adopted at the moment of executing the readings. Aiming to provide information to guide the technical and scientific environment regarding the right use of this type of non-destructive testing, the objective of this work is to evaluate some possible factors influencing the reading of corrosion potential, such as: moisture content of the concrete, water/cement ratio, thickness of the concrete cover and degree of contamination by chlorides. Results indicate that moisture and degree of contamination of the concrete by chloride ions had a tendency of making the corrosion potential more electronegative. Besides, it was verified that the influence of the cover is different for the case of contaminated concrete (1% of chlorides by mass of cement) and not contaminated with chlorides: the influence of the thickness of the cover, in the case of concrete contaminated by chlorides, was inversely proportional, in other words, the greater the cover thickness is, the less electronegative the value of the corrosion potential will be. On the other hand, in cases of concretes without chlorides, the effect of the cover thickness in the readings or corrosion potential was irrelevant. All this information was proved with 95% of statistical significance.

Molybdates as Corrosion Inhibitors in the Presence of Chlorides

CORROSION ◽  
1976 ◽  
Vol 32 (7) ◽  
pp. 263-266 ◽  
Author(s):  
E. A. LIZLOVS
Keyword(s):  
Weight Loss ◽  
Corrosion Rate ◽  
Potentiodynamic Polarization ◽  
Room Temperature ◽  
Corrosion Inhibitors ◽  
Corrosion Potential ◽  
Chloride Content ◽  
Passive State ◽  
Chloride Sulfate ◽  
Polarization Studies

Abstract The effect of the molybdate ion (MoO4=) concentration on the corrosion inhibition of 1010 steel was investigated in aerated chloride/sulfate-containing solutions. The chloride content was 304 ppm Cl−, and the sulfate was 352 ppm SO4=. Weight loss measurements and electrochemical methods were employed for the investigation. The pH was controlled at 8.7. Weight loss measurements indicated that about 165 ppm of molybdate reduced the corrosion rate below 10 mg·dm−2/day at room temperature. At 160 F (71 C), about 50 ppm of molybdate reduced the corrosion rate to 4 to 5 mg·dm−2/day. The potentiodynamic polarization studies and the examination of corrosion potential and immersion time relationship disclosed that the molybdate ion acts as a passivating agent in the presence of oxygen. Passivity was also obtained under potentiodynamic polarization conditions in a nitrogenated solution. No passivation was obtained in the absence of the molybdate ion. For spontaneous passivation, both molybdate and oxygen (oxidizing agent) were needed. Corrosion rates in a passive state according to the polarization curve should be nil.

scholarly journals Modeling of Corrosion Rate and Resistivity of Steel Reinforcement of Calcium Aluminate Cement Mortar

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Cristina Argiz ◽  
Miguel Ángel Sanjuán ◽  
Pedro Castro Borges ◽  
Emiliano Álvarez
Keyword(s):  
Corrosion Rate ◽  
Calcium Aluminate ◽  
Cement Mortar ◽  
Chloride Content ◽  
Chloride Ions ◽  
Steel Reinforcement ◽  
Calcium Aluminate Cement ◽  
Ohmic Drop ◽  
Corrosion Intensity ◽  
Aluminate Cement

Calcium aluminate cement (CAC) is a binder whose hydrated compounds change over time from cubic phases to hexagonal phases, producing an increase of porosity in reinforced concretes. Thereby, chloride ions, among other steel corrosion promoters, can enter the concrete more easily leading to an increase of the reinforcement corrosion process. When such a transformation of phases is completed, a characteristic value regarding both corrosion intensity (Icorr) and resistivity (related to the ohmic drop of the cementitious material) is reached, which depends mainly on the mix proportions of the material and the curing procedure. This paper presents the characteristic corrosion intensity values of steel embedded in mortars made of CAC after five years of exposure to either a 0.5 mol/l or 1.5 mol/l NaCl solution in order to be applied to estimate the service life of reinforced concrete made of calcium aluminate cement (CAC) which is used in real construction structures. Ohmic drop measurements are also presented to support the values obtained. The aim of this paper is to model the corrosion rate and resistivity of the steel reinforcement of calcium aluminate cement mortar with regard to environmental factors (temperature and chloride content) and mortar quality (water/cement ratio).

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.

scholarly journals Combined Freeze-Thaw and Chloride Attack Resistance of Concrete Made with Recycled Brick-Concrete Aggregate

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7267
Author(s):  
Yao Yu ◽  
Jian Wang ◽  
Ninghui Wang ◽  
Chenjie Wu ◽  
Xiaojing Zhang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fly Ash ◽  
Sodium Chloride ◽  
Chemical Properties ◽  
Chloride Content ◽  
Chloride Ions ◽  
Water Soluble ◽  
Concrete Aggregate ◽  
Freeze Thaw ◽  
Chloride Attack

The objective of this study was to investigate the physico-chemical properties of concrete made with recycled brick-concrete aggregate, which was the mixture from waste concrete and waste clay brick in a 7:3 ratio. Specifically, this paper investigated the mechanical properties, freeze-thaw resistance, and distribution of water-soluble chloride ions of concrete containing RBCA and fly ash (FA) against combined freeze-thaw and sodium chloride attack. Concrete containing RBCA replacement of natural coarse aggregate and fly ash replacement of Portland cement was subjected to 45 freeze-thaw cycles containing sodium chloride solution. It was discovered that the mechanical properties and freeze-thaw resistance to sodium chloride attack gradually decreased with increasing RBCA content. At the same time, a replacement level of 15% FA by weight resulted in significant improvements in compressive strength and resistance to combined freeze-thaw and chloride attack. Furthermore, using a replacement of 30% FA by weight markedly improved the resistance to chloride ion penetration of concrete due to the lowest water-soluble chloride content.

The Effect of Trace Boron Element on Local Corrosion Resistance of Casted 0.04C-16Cr Ferritic Stainless Steel

2011 ◽  
Vol 415-417 ◽  
pp. 800-806 ◽  
Author(s):  
Tie Ming Guo ◽  
Ding Cang Zhang ◽  
Zhi Hui ◽  
Chang Song Han ◽  
Li Ming Zhao
Keyword(s):  
Stainless Steel ◽  
Corrosion Resistance ◽  
Nitric Acid ◽  
Corrosion Rate ◽  
Ferritic Stainless Steel ◽  
Pitting Corrosion ◽  
Intergranular Corrosion ◽  
Corrosion Potential ◽  
Chloride Ions ◽  
Curve Method

0.04C-16Cr and 0.04C-16Cr containing 26ppm B ferritic stainless steels were smelted by using a vacuum induction furnace. Then 65% boiling nitric acid method and the electrochemical potentiokinetic reactivation method (EPR) were used to research their intergranular corrosion sensitivity. Meanwhile, electrochemical test method (Tafel polarization curve method, the anode circular polarization curve method) and chemical immersion method were used to research their pitting corrosion resistance. The results showed that the corrosion rate of 0.04 C-16Cr stainless steel containing 26ppm B in 65% boiling nitric acid is lower than that of 0.04 C-16Cr stainless steel. The reactivation rate of 0.04C-16Cr containing 26ppm B in dilute sulphuric acid medium significantly reduced compared with that of 0.04C-16Cr. The pitting corrosion potential, self-corrosion potential and the value of (Eb-Ep) of the stainless steel containing with 26ppm B in chlorideions medium reduced, while the corrosion rate increased compared with the stainless steel without B addition. It indicates that trace boron addition improves the intergranular corrosion resistance and repair ability of the passive film of the 0.04C-16Cr ferritic stainless steel after pitting corrosion process in chloride ions medium, but it also promotes the pitting corrosion tendency of the steel. Besides, introduction B to 0.04C-16Cr ferritic stainless steel reduces the steel’s corrosion resistance in active dissolved zone and promotes its intergranular corrosion tendency in chloride ions medium. The electrochemical characteristics of local corrosion are consistent with the results of chemical immersion test.

Sign in / Sign up

Export Citation Format

Share Document