Surface Of Steel Bar Research Articles

Investigation of corrosion mechanism of ribbed mild steel bars coated with magnesium potassium phosphate cement paste

This study investigated the anti-corrosion performance of magnesium potassium phosphate cement (MKPC) paste applied to the surface of ribbed mild steel bars – which was exposed to simulated accelerated corrosive environment. Four electrochemical approaches were used including open-circuit potential (OCP), electrochemical impedance spectroscope (EIS), polarization resistance (PR) and potentiodynamic polarization (PDP) over a period of 5376 h (224 days). Moreover, visual inspection, optical microscope, and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) were used to assess the extent of corrosion on the samples. To understand the mechanism of corrosion protection of the coating system, X-ray photoelectron spectroscopy (XPS) was employed to characterize the chemical groups on the surface of mild steel, and the chemical changes in the coating layer were characterized using thermogravimetric/differential thermal analysis (TG/DTA) and X-ray diffraction (XRD). The MKPC paste coated bars were compared with not only uncoated bars, but also bars coated with ordinary Portland cement (OPC) that is known to passivate steel due to its high alkalinity. Results indicated that MKPC paste coating layer could effectively protect the ribbed mild steel bars, and its protectiveness significantly surpassed that of OPC. Both the de-passivation effects of chloride ions and carbonation of the OPC resulted in relatively severe corrosion of the OPC coated bars during the long exposure duration; while the anti-corrosion merit of the MKPC paste coating layer could be attribute to a double-protection system– the dense microstructure of MKPC and the formation of an iron (III) phosphate passivation layer between the substrate steel and the MKPC paste coating layer.

Enhancing the corrosion resistance of recycled aggregate concrete by incorporating waste glass powder

Conventional supplementary cementitious materials would decrease the alkalinity of pore solution, which is not beneficial for the stabilization of passive film on the surface of steel bars in the marine environment. By leverage of the alkali-rich and pozzolanic characteristics, this study first valorized waste glass powder (GP) to enhance the corrosion resistance of recycled aggregate concrete (RAC). The results showed that partially replacing cement with GP could improve the steel corrosion resistance of RAC to a level better than conventional concrete prepared with natural aggregates. Moreover, the presence of 20% GP significantly enhanced the chloride penetration resistance at a later age without sacrificing the compressive strength. The enhanced corrosion resistance of GP-RAC was attributed to two main reasons: i) the refined pore structure by the formation of secondary C-(N)-S-H gels with a lower Ca/Si ratio; ii) the increased alkalinity of pore solution due to the depolymerization of GP and the released Na+ from GP. As a result, the use of GP in low-carbon cement was able to compensate for the inferior durability of RAC. The proposed corrosion-resistant concrete with low ecological and economic costs has a promising application potential to promote the wider use of GP and RAC in the construction sector.

Improved interfacial interactions and corrosion resistance of epoxy coated reinforcement by pre-electrodeposited silane layer

Epoxy coating is one of the most useful measures for corrosion protection of steel bar due to the facile operation and excellent barrier property. However, the high brittleness and porosity of epoxy coating as well as the weak interface bonding properties between epoxy and steel bar greatly limited its protective performances. In this work, a uniform silane layer was prefabricated on the surface of steel bar by electrodeposition to enhance the interfacial interactions between steel bar and epoxy, and thus enhance the protective properties of the coating. The surface features and corrosion resistance of the prepared silane-epoxy composite coatings were studied by means of scanning electron microscope, Fourier transform infrared spectroscopy, Raman analyses, electrochemical and Machu tests. The results show that the presence of the electrodeposited silane layer significantly increases the chemical bond between carbon steel and epoxy resin, thereby enhance the adhesion between epoxy resin and carbon steel. In addition, the network structure formed by silane acts as a physical barrier to the corrosive medium, improving the corrosion resistance of single epoxy coating, thereby delaying the corrosion of carbon steel.

Effect of recycled aggregate and supplementary cementitious material on the chloride threshold for steel bar corrosion in concrete

Under marine environment, the passive film on the surface of steel bar embedded in reinforced concrete structures will be broken once a threshold value of chloride, i.e., chloride threshold (Cth), is reached at the rebar-concrete interface by diffusing through the concrete cover. The value of Cth is essential for determining service life of concrete structures. In this investigation, the effect of recycled aggregate (RA, i.e., recycled coarse aggregate) and supplementary cementitious material (SCM), including ground granulated blast furnace slag, red mud and glass powder, on the value of Cth was investigated. A chloride threshold test method for accurate determination of Cth was proposed by the alternation of accelerated chloride migration test and artificial-natural diffusion test, which can simulate the marine environment and accelerate the diffusion of chloride. The corrosion activity of steel bar was monitored using two electrochemical methods, including linear polarization resistance method and macro-cell corrosion method, to detect the initiation of corrosion. Immediately after the corrosion initiation, corresponding specimen was taken out to measure the chloride content of concrete adjacent to the surface of steel bar. A calculating method of chloride threshold Cth was presented considering the actual distribution of coarse aggregate in concrete adjacent to the surface of steel bar. The results of the chloride threshold tests show that RA and SCM have a significant influence on the protective properties of passive films, and it is worth noting that the positive effect of RA on the quality of passive film has been observed. For concrete with the same substitution level of SCM, the chloride threshold Cth increases linearly with RA content. Subsequently, the suggested values of Cth for natural aggregate concrete (NAC) with different substitution level of SCM are given, and the suggested values of Cth for corresponding recycled aggregate concrete can be given by an amplified factor kRA multiplied by Cth for NAC with ± 10% relative error.

Comparison of erosion performance of uncladded and WC-based laser cladded SS304 and SS410 steels

Myriad hydro materials have been encountered with the severe attacks of eroded particles during the operation, leading to degradation of target material and economic loss. In this study, Colmonoy-6+WC powders were deposited with the help of the laser cladding method on the bare SS304 and SS410 steel surfaces. Distinct properties of cladded surfaces, such as mechanical as well as metallurgical properties, were investigated. The influence of slurry erosion parameters like angle of impact and impact velocity of eroded particles on the cladded as well as uncladded steel specimen was analysed. Under all slurry erosion conditions, there was an escalation in slurry erosion resistance in the case of cladded steel as that of as-received steel specimens. In slurry erosion, the influence of the impact velocity of erodent particles is more against the impact angle. The scanning electron microscopy images of eroded uncoated steel specimens represent ductile behaviour along with the formation lip, ploughing etc., while eroded cladded steels exhibit brittle behaviour.

Environmental effects on condition assessments of concrete structures with ground penetrating radar

Reflection amplitude from rebar is the most commonly used parameter for condition assessment of concrete structures using Ground-Penetrating Radar (GPR). However, it was reported that such amplitudes might affect by several factors, including the chloride content, rust accumulated on the surface of steel bars due to corrosion, and the environmental conditions at the time of GPR data collection. The objectives of this study were to observe the change of GPR signals over time and to evaluate the effects of those factors on the reflection amplitude of steel bars. A series of six reinforced concrete slabs were fabricated with identical configurations but for different chloride contents. Two testing phases with the multiple GPR measurements were conducted both outside and inside an environmental chamber. In the first testing phase, the development of GPR signals was daily obtained from day one to day 90 in the laboratory conditions. In the second testing phase, the GPR data were collected inside the environmental chamber at an interval of 24 h. Relative Humidity (RH) was set at three levels of 55%, 70%, and 85%, respectively, while the temperature was varied between 5 °C and 40 °C. The test results from the first testing phase showed that the GPR signals developed at an exponential rate during the first three months. In addition, results from the second testing phase revealed that both the added chloride and the rust on the surface of steel reinforcement reduced the amplitude of rebar reflection. Regarding the effects of temperature, for sound (i.e., non-contaminated) concrete, the reflection amplitude decreased approximately 0.05 dB for every 1 °C increments. For the contaminated concrete, such ratio was found to increase proportionally to the chloride levels. Finally, the RH was observed to have insignificant effects on the amplitude of rebar reflection.

Influence of Rust Inhibitors on the Microstructure of a Steel Passive Film in Chloride Concrete

To compare the corrosion inhibition behaviors of rust inhibitors with different mechanisms on steel bars, the rust resistance effect of sodium molybdate (Na2MoO4), sodium chromate (Na2CrO4), benzotriazole (BTA), N-N dimethyl ethanolamine, sodium molybdate (Na2MoO4) + benzotriazole (BTA), and sodium chromate (Na2CrO4) + benzotriazole (BTA) on steel bars in a simulated chloride concrete pore solution was studied. The rust resistance effects of different types of rust inhibitors were assessed by electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The effects of different types of rust inhibitors on the film formation characteristics of a passive film on a steel bar surface were expounded. The results show that: When sodium molybdate (Na2MoO4) and benzotriazole (BTA) acted together, the impedance value and the capacitive reactance arc radius were the largest, and the density of the passive film and the inhibition efficiency were the highest. The composition of the passive film was primarily composed of iron compounds, and it also contained oxide and adsorption films that were formed on the steel bar surface by the rust inhibitors. The rust resistance effect was proportional to the compactness of the passive film.

Engineering of corrosion product-polymer hybrid layers for enhanced CO2 corrosion protection of carbon steel part two: Computational investigation and surface characterisation

Carbon dioxide internal corrosion of carbon steel pipelines remains a major issue that is typically mitigated via the addition of corrosion inhibitors. In specific operational environments, a protective natural corrosion product layer known as iron carbonate (FeCO 3 ) can evolve on internal pipeline walls, providing comparable corrosion inhibitionefficiency to that achieved from surfactants. However, in some instances, incomplete corrosion product coverage can initiate localised corrosion. In our previous work, we demonstrated the ability of Poly (allylamine hydrochloride) (PAH) to act synergistically with FeCO 3 when the corrosion product exhibits partial coverage of ×65 carbon steel surfaces in an aqueous CO 2 corrosion environment. In this work, we employ density functional theory (DFT) to show that PAH is able to coordinate with both FeCO 3 and the bare carbon steel surface, producing a FeCO 3 -PAH hybrid structure. The surface and chemical properties of a naturally formed FeCO 3 and the FeCO 3 -PAH hybrid layers are characterised employing scanning electron microscopy (SEM) coupled with focused ionic beam (FIB), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD) and X-ray photoelectron spectroscopy (XPS). • The PAH molecules adsorb onto the carbon steel surface and corrosion product (FeCO 3 ) via chemisorption and physisorption. • The PAH molecules interact with FeCO 3 through coordination and hydrogen bonding producing a hybrid layer. • The PAH centres of interaction with film-free carbon steel and FeCO 3 film are protonated and neutral amine groups. • The crystal structure and layer thickness of FeCO 3 and FeCO 3 -PAH hybrid layers are characterised and compared.

Investigation of Various Coating Resins for Optimal Anticorrosion and Mechanical Properties of Mild Steel Surface in NaCl Solution

The primary objective of the research was to investigate the ideal resin coating on the mild steel surface among various resin coatings which are in use. These resin coatings are used as an anti-corrosive material for mild steel surfaces with enhanced mechanical properties. The resins (epoxy, polyurethane, polyester, and phenolic) on mild steel surface were applied by the pneumatic spray coating method. In addition, immersion test and salt spray test methods were followed using sodium chloride (NaCl) solution. Furthermore, the rate of corrosion and mechanical properties of mild steel coated with different resins was evaluated by conducting various experiments (immersion test, salt spray test, tensile strength test, and scratch hardness test) and was compared with a bare mild steel surface. The results of the current research showed that the mild steel surface coated with epoxy resin was found to be the most effective corrosion resistance material with better mechanical properties compared to other tested mild steel resin-coated surfaces.

Engineering of corrosion product-polymer hybrid layers for enhanced CO2 corrosion protection of carbon steel part one: Corrosion study and mechanical property investigation

The role of Poly (allylamine hydrochloride) (PAH) is investigated when applied in-situ during different stages of evolution of an iron carbonate (FeCO3) corrosion product on X65 carbon steel surfaces in a CO2 corrosion environment. We show that PAH adsorbs onto both FeCO3 and the bare carbon steel surface, producing a FeCO3-PAH hybrid structure that reduces both localised and general corrosion. The thickness and mechanical properties of naturally formed FeCO3 and FeCO3-PAH hybrid layers are characterised. The hybrid layers are shown to offer superior adhesion, as well as increased elasticity and delamination resistance compared with the naturally formed FeCO3 layer.

Study on the bond behavior between steel bar with different derusting methods and concrete

In this paper, three different derusting methods: angle grinder, rust remover and shot blasting machine were selected to remove the corrosion products on the surface of steel bars with different corrosion ratios. The bond behavior between steel bars and concrete after different derusting methods was experimentally studied. To carry out this study, deformed steel bars with diameters of 14 mm, 18 mm, 22 mm and 25 mm were selected to conduct corrosion in the natural environment and 36 center-pulled specimens were cast. The following contents were studied during the test: (1) the weakening of the surface rib height of steel bar after various derusting methods; (2) the effects of derusting methods, corrosion ratio and steel bar diameter on the bond strength and peak slip were studied, the influence mechanism of various factors on the bond performance of specimens was revealed, and the influence law of various factors on the bond performance of specimens was summarized; (3) the bond-slip constitutive relation between steel bar and concrete with different diameters after different derusting methods were studied.

Ceria particles synthesized via combustion method to inspire active protection for epoxy coating on mild steel

This research aims to study the effect of fuel type in the combustion synthesis of CeO2 particles on their corrosion inhibitive activity in an epoxy coating. For this purpose, four different types of CeO2 particles were prepared using urea, glycine, glucose, and citric acid as the fuel source. The release of Ce4+ cations from CeO2 particles in 3.5% NaCl solution was assessed by inductively coupled plasma (ICP) analysis. The results indicated that CeO2 particles synthesized by urea (URE) released about ten times more cerium cations compared to the CeO2 particles synthesized by other fuels. The corrosion behavior of bare steel in saline solution in the presence and absence of released Ce4+ cations and the corrosion inhibitive performance of scratched coatings containing CeO2 particles were assessed by electrochemical techniques. Results showed considerable improvement in the impedance values in both solution and coating phases, specifically in the presence of URE. Besides, field emission scanning electron microscopy (FESEM) and energy dispersive spectroscopy (EDS) were utilized to characterize the bare steel surface and the scratched area of coated samples after exposure to the test solutions. Surface analysis results showed that the least corrosion products were formed on the URE sample, confirming its highest inhibitive activity. The adhesion and protective behavior of epoxy coatings were also determined by pull-off and salt spray tests, respectively. Overall, the results revealed that the CeO2 particles synthesized by urea showed the highest anti-corrosion properties due to their highest capability to release the Ce4+ cations.

Corrosion behavior of HRB400 and HRB400M steel bars in concrete under DC interference

The influence of direct current interference on the corrosion behavior of HRB400 and HRB400M steel bars in simulated concrete solution was studied using methods such as weight loss experiment, electrochemical experiment, surface technology and product analysis. The research results showed that with the increase of DC interference voltage, the corrosion rates of HRB400 and HRB400M steel bars would increase. The corrosion resistance of HRB400M steel bars was better than HRB400 steel bars under the experimental conditions. In addition, direct current interference could cause damage to the corrosion product layer on the surface of HRB400 steel bars and HRB400M steel bars. And the corrosion form and corrosion product types of HRB400 and HRB400M steel bars would be affected by direct current interference. The main corrosion products of HRB400 steel bars included γ-FeOOH and Fe2O3 when it was not interfered by DC. When DC interference was applied, the main corrosion products included Fe3O4 and Fe2O3. The corrosion products on the surface of HRB400M steel bars were mainly Fe3O4 and Fe2O3, and the types of products increased to form Cr2O3 and MnFe2O4.

Experimental study on multi-component corrosion inhibitor for steel bar in chloride environment

This paper investigates one type of multi-component corrosion inhibitor for steel bars in chloride environment. Triethanolamine (TEA), tri-isopropanolamine (TIPA), sodium monofluorophos-phate (MFP) and sodium molybdate (T-4) were proportioned to prepare this multi-component corrosion inhibitor. Corrosion behavior of steel bar was evaluated using the polarization curve, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The polarization curves were fitted using the adsorption isotherm models. Experimental results indicated that the steel bar corrosion in chloride solution can be reduced by the addition of either organic or inorganic corrosion inhibitors. This is attributed to the fact that organic corrosion inhibitor can form an adsorption film on the steel bar surface and inorganic corrosion inhibitor abates electrochemical reaction of steel bars. Compared to single component corrosion inhibitors, the corrosion rate of steel bars in simulated pore solution was significantly restrained by the multi-component corrosion inhibitor. The adsorption of multi-component corrosion inhibitor on the surface of steel bar can significantly reinforce the passive film by means of physical (organic) or chemical (inorganic) process. For all the investigated corrosion inhibitors, the adsorption isotherms were in good agreement with experimental results. The EIS result and equivalent electrochemical circuit confirmed the chemical reaction and physical adsorption process of the multi-component corrosion inhibitor. Therefore, the chloride induced corrosion of steel bars can be effectively controlled by the multi-component corrosion inhibitor.

Interfacial assembled mesoporous polydopamine nanoparticles reduced graphene oxide for high performance of waterborne epoxy-based anticorrosive coatings

Embedding two-dimension micro/nanocontainers containing corrosion inhibitors into organic coating is a well-established concept to impart the coating with enhanced barrier and self-healing feature. Herein, a versatile nanoemulsion assembly approach was used to synthesis nanocarriers combing mesoporous polydopamine nanoparticles (MPDA) with reduced graphene oxide (GO), which was employed to encapsulate corrosion inhibitors (benzotriazole, BTA) to improve the anticorrosion performance of waterborne epoxy coating. The BTA release profiles from synthesized GO with MPDA (PDAG) demonstrated the rapid pH-triggered activities to acidic corrosion environment. With the addition of BTA-loaded PDAG, the composited epoxy coatings presented self-repairing behavior and enhanced corrosion resistance during long-term immersion. The outstanding anticorrosion performance is attributed to dual-protection mechanism provided by BTA-loaded PDAG: (1) MPDA endows GO with satisfactory interface compatibilities and thus provides impermeable barrier to delay the penetration process of corrosive electrolyte; (2) corrosion inhibitors including BTA and polydopamine form the adsorption layers on bare steel surface to resist continuous corrosion at metal/coating interface.

Experimental investigation of crack width variation along the concrete cover depth in reinforced concrete specimens with ribbed bars and smooth bars

Crack width variation along the concrete cover depth has been studied from the past for better understanding of the cracking phenomenon in reinforced concrete (RC) structures. Previous studies have highlighted important cracking behaviors like internal cracks. The behavior of ‘slip’ between the reinforcement and concrete and the formation of a nonuniform crack face along the concrete cover depth are still not very clearly understood. An experimental program has been conducted to study the crack width variation along the cover depth in concrete prisms reinforced with a central ribbed bar and smooth bar, by varying the concrete cover depths. Both in specimens with smooth bars (SS) and specimens with ribbed bars (SR), crack width is larger on the concrete surface than at the steel bar surface. The crack width at the reinforcement is considerably larger in the SS than in the SR. In the SR, the crack width increases from the reinforcement along the cover depth bi-linearly, while, in the SS, it increases linearly. For the SR, the aforementioned behavior is due to the occurrence of internal cracks. In the SS, significant slip has been identified at the reinforcement and concrete interface, whereas negligible slip has been observed in the SR. A surface crack width calculation model has been developed, considering both the strain difference and the effect of the nonuniform crack face along the concrete cover depth. Its predictions showed good agreement with the experimental surface crack widths from the conducted study and with the results from the experiments in literature.

Restriction of Cl- and SO4 2- Ions Transport in Alkali Activated Slag Cement Concrete in Seawater

The relevance of alkali activated slag cement (AASC) concretes for structures operated in seawater is due to their enhanced resistance in aggressive environments. The application of high consistency fresh concretes is accompanied by negative changes in their structure with higher penetration of aggressive environments. Thus, the methods to prevent corrosion of steel reinforcement in plasticized AASC concrete are actual for investigations. It is shown, that modification of plasticized AASC concrete (consistency class S4) by the complex «alumina cement - portland cement - clinoptilolite - trisodium phosphate (Na3PO4·12H2O)» restrict the transport of aggressive Cl- and SO4 2- ions. The results of DTA, XRD, electron microscopy, microzond analysis show that mentioned complex limits transport of the mentioned aggressive ions due to their binding by AFm phases in hydration products, exchange with OH- ions in the structure of clinoptilolite, formation of hydrated products of apatite group Ca5(PO4)3(OH, Cl). This was confirmed by qualitative reaction on Cl- and SO4 2- ions in concrete structure, as well as by assessing of surface and mass loss of steel bars embedded in AASC concrete after 9 months in seawater. It was ensured the advanced crystallization with densification of microstructure, which increases corrosion resistance of artificial stone.

Chloride corrosion resistance of double-layer anticorrosive coating in simulated concrete pore solution

Steel reinforced concrete structures are widely used in construction projects due to their low cost and high load-bearing capacity. The service life is inevitably reduced because of the steel corrosion during service. Here, a double-layer anti-corrosion strategy was proposed for the low carbon steel used in chloride corrosion environment. A super-hydrophobic anti-corrosion coating was fabricated on the surface of low carbon steel bars by an environment-friendly and safe method. The corrosion resistance of super-hydrophobic low carbon steel was studied in a chlorine-containing simulated concrete pore solution. Electrochemical test results showed that super-hydrophobic low carbon steel had better chlorine corrosion resistance than ordinary low carbon steel. Moreover, the effects of three different modification methods on the chloride corrosion resistance of super-hydrophobic low carbon steel were compared. The results of electrochemical tests and corrosion immersion experiments showed that the super-hydrophobic surface obtained through a combination of physical and chemical modification had good corrosion resistance. The corrosion inhibition rate of the super-hydrophobic samples was up to 97.1%. It is expected that the super-hydrophobic low carbon steel with a dual anti-corrosion layer will play a significant role in the corrosion protection of steel reinforced concrete structures.

Numerical study on the effect of transverse crack self-healing on the corrosion rate of steel bar in concrete

Reinforced concrete is subject to degradation by cracking of the concrete and corrosion of the steel reinforcing bars. This study explores the influence of transverse crack self-healing on the corrosion rate of steel bars by developing a deformed mesh model. The dynamics of transverse cracking and steel bar surface potential distributions are also explored, and parameter sensitivity analysis of the corrosion current density is conducted. The results show that steel bars have a lower surface potential at transverse cracks than in non-cracked areas, which decreases with exposure time. Crack self-healing not only reduces the corrosion rate and surface potential of steel bars but also reduces the rate of chloride-ion diffusion into concrete. Increasing the thickness of the concrete's protective layer is an effective way to slow the corrosion of steel bars.

A mussel-inspired delivery system for enhancing self-healing property of epoxy coatings

Dopamine (DA), one type of mussel-inspired biological molecules with adhesive nature and corrosion inhibitor property, are often used to functionalize the surfaces of various materials. Herein, we report the application of polydopamine (PDA) microcapsules as novel nanocontainers for the purpose, loading corrosion inhibitor (benzotriazole) in its shell structure, and then were embedded into epoxy coatings to provide self-healing and anti-corrosion protection for carbon steel. Fast release of benzotriazole in acidic environment caused by local corrosion and the chelating effect of PDA-Fe3+ can synergistically promote the formation of protective film on bare steel surface, which endows coatings with self-healing functionality. Electrochemical impedance spectroscopy (EIS), local electrochemical impedance spectroscopy (LEIS), and spray tests were conducted to evaluate the active inhibition and corrosion resistance of the loaded coatings. The scratched coating with incorporation of nanocontainers presented better protection performance, exhibiting increased Ro (oxide layer resistance) and Rct (charge transfer resistance) during initial immersion periods. The EIS tests in long-term immersion were also performed to confirm the anti-corrosion effect of composited coatings. These results demonstrated that benzotriazole-decorated PDA capsules dramatically enhanced the self-healing properties and anti-corrosion performance of epoxy coatings with the synergistic help of PDA and benzotriazole.