Galvanized Steel Reinforcement Research Articles

Electrochemical Assessment of Galvanized Steel Corrosion in Alkaline Sulfate Solution

Corrosion of steel prestressing strand in bonded post-tensioned bridge tendons have been associated with elevated concentrations of sulfate ions in deficient grout that can develop due to grout segregation [1]. Previous research indicated that the early presence of elevated sulfate ion concentration in the deficient grout in contact with the embedded steel can impair steel passivity. Metastable pitting was observed for steel in saturated calcium hydroxide solutions with sulfate ion concentrations greater than 1,300 ppm and pitting was observed in solutions above 20,000 ppm [2-4]. In addition to steel strand corrosion, galvanized steel ducts in direct contact with the deficient grout with elevated sulfate ion concentrations were also observed to have severe localized corrosion [1]. Galvanized steel in alkaline solutions, such as in cement pore water, have been characterized to have greater resistance to chloride-induced corrosion with chloride threshold concentrations as much as 2.5 times greater than carbon steel [5]. Information relating to sulfate concentrations is less available. Electrochemical testing including the electrochemical noise (EN) technique was conducted to identify the role of early sulfate ion presence on corrosion of galvanized steel.EN provides a test method to assess the corrosion modality without the influence of an external excitation that can affect the electrode surface and electrolyte chemistry (such as metal oxidation and oxygen reduction) [6-7]. The testing aims to identify the corrosion mitigation characteristics of the galvanized steel such as zinc activity and protective barrier surface oxide layers in presence of sulfate ions as well as combined cases with chloride ion contamination below reported threshold concentrations for galvanized steel. In the testing here, steel specimen were exposed to alkaline solutions simulating pore solutions with pH 12.6 with varying sodium sulfate levels and sodium chloride. Supplemental electrochemical experiments included the steady-state condition (open circuit potential, linear polarization test, and electrochemical impedance spectroscopy). References K. Lau, and I. Lasa. "Corrosion of prestress and post-tension reinforced-concrete bridges." Corrosion of steel in concrete structures. Woodhead Publishing, 2016. 37-57. DOI: https://doi.org/10.1016/B978-1-78242-381-2.00003-1.S. Permeh, K. K . Krishna Vigneshwaran, K.Lau., and I.Lasa. “Corrosion of Post-Tensioned Tendons with Deficient Grout. Part 3: Segregated Grout with Elevated Sulfate and Vestigial Chloride Content.” Corrosion 75 (2019) pp.848-864.S. Permeh, K. Lau, M. Duncan, and R. Simmons. “Initiation of localized steel corrosion in alkaline sulfate solution.” Materials and Structures, 54 (2021), pp.1-17.S. Permeh, K. Lau, M. Duncan, and R. Simmons. “Identification of steel corrosion in alkaline sulfate solution by electrochemical noise.” Materials and Corrosion, 72(2021), pp.1456-1467.S. Yeomans. Galvanized steel reinforcement in concrete. Elsevier, 2004.S. Permeh, and K. Lau. "Electrochemical Behavior of Steel in Alkaline Sulfate Solutions with Low Level Chloride Concentrations." ECS Meeting s. No. 10. IOP Publishing, 2021.K. Lau, S. Permeh. “Assessment of durability and zinc activity of zinc-rich primer coatings by electrochemical noise technique.” Progress in Organic Coatings, 167(2022): 106840.

Electrochemical Corrosion of Galvanized Steel in Binary Sustainable Concrete Made with Sugar Cane Bagasse Ash (SCBA) and Silica Fume (SF) Exposed to Sulfates

This research evaluates the behavior corrosion of galvanized steel (GS) and AISI 1018 carbon steel (CS) embedded in conventional concrete (CC) made with 100% CPC 30R and two binary sustainable concretes (BSC1 and BSC2) made with sugar cane bagasse ash (SCBA) and silica fume (SF), respectively, after 300 days of exposure to 3.5 wt.% MgSO4 solution as aggressive medium. Electrochemical techniques were applied to monitor corrosion potential (Ecorr) according to ASTM C-876-15 and linear polarization resistance (LPR) according to ASTM G59 for determining corrosion current density (icorr). Ecorr and icorr results indicate after more than 300 days of exposure to the sulfate environment (3.5 wt.% MgSO4 solution), that the CS specimens embedded in BSC1 and BSC2 presented greater protection against corrosion in 3.5 wt.% MgSO4 than the specimens embedded in CC. It was also shown that this protection against sulfates is significantly increased when using GS reinforcements. The results indicate a higher resistance to corrosion by exposure to 3.5 wt.% magnesium sulfate two times greater for BSC1 and BSC2 specimens reinforced with GS than the specimens embedding CS. In summary, the combination of binary sustainable concrete with galvanized steel improves durability and lifetime in service, in addition to reducing the environmental impact of the civil engineering structures.

Durability Assessment of Recycled Aggregate HVFA Concrete

The possibility of producing high-volume fly ash (HVFA) recycled aggregate concrete represents an important step towards the development of sustainable building materials. In fact, there is a growing need to reduce the use of non-renewable natural resources and, at the same time, to valorize industrial by-products, such as fly ash, that would otherwise be sent to the landfill. The present experimental work investigates the physical and mechanical properties of concrete by replacing natural aggregates and cement with recycled aggregates and fly ash, respectively. First, the mechanical properties of four different mixtures have been analyzed and compared. Then, the effectiveness of recycled aggregate and fly ash on reducing carbonation and chloride penetration depth has been also evaluated. Finally, the corrosion behavior of the different concrete mixtures, reinforced with either bare or galvanized steel plates, has been evaluated. The results obtained show that high-volume fly ash (HVFA) recycled aggregate concrete can be produced without significative reduction in mechanical properties. Furthermore, the addition of high-volume fly ash and the total replacement of natural aggregates with recycled ones did not modify the corrosion behavior of embedded bare and galvanized steel reinforcement.

Lime Addition Effect on Corrosion of Reinforced Mortar

This study aims to investigate the effect of lime addition in cement mortar on corrosion resistance of carbon and galvanized steel reinforcements. Mixed mortars were studied containing three contents of lime (6.7, 13.3, and 26.3 wt.%). The water retention, incorporated air, and compression strength of reinforced mortars were determined. Immersion tests were performed using the reinforced mortars consisting of 12 cycles of immersion in a solution of 3.5% (wt./v) sodium chloride and drying in a stove at 60oC. Electrochemical impedance spectroscopy was used to monitoring reinforcement corrosion after cyclic tests. These measurements were repeated after 36 months of the cyclic immersion testing. After the cyclic immersion tests in a saline solution, the polarization resistance of carbon and galvanized steel reinforcement increased as the lime content in mortar increased, demonstrating the protective effect of lime. After 36 months, the polarization resistance of steels in mixed mortars with the highest lime content was the lowest. For the carbon and galvanized steel in cement and mixed mortars, the polarization resistance increased after 36 months of the cyclic test. Keywords: Lime. Mortar. Reinforcement corrosion. Electrochemical impedance spectroscopy.

Outline of Japan Society of Civil Engineers (JSCE) Guideline on Design and Application Methods of Galvanized Steel Reinforcement for Concrete Structures

Outline of Japan Society of Civil Engineers (JSCE) Guideline on Design and Application Methods of Galvanized Steel Reinforcement for Concrete Structures

Effect of soluble inhibitors on the corrosion behaviour of galvanized steel in fresh concrete

The effect of some soluble inhibitors on the passivation time of galvanized steel reinforcements in fresh concrete was studied in order to reduce H2 evolution associated with the active corrosion. The investigation was performed by means of corrosion potential monitoring, scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction analysis. The obtained results indicate that the passivation of galvanized steel in concrete containing chromates occurs in three steps with different mechanisms and that dissolved oxygen is necessary for the beginning of passivation process. Among the inhibitors studied as alternative to Cr VI, nitrite seem the most promising one, even if it is less effective than chromate. Diethanolamine and molybdate ions do not have significant effect on the passivation time of galvanized steel in fresh concrete.

Corrosion behaviour of bare and galvanized steel in geopolymer and Ordinary Portland Cement based mortars with the same strength class exposed to chlorides

The corrosion behaviour of bare and galvanized steel reinforcements in geopolymeric and cementitious mortars, at three strength classes, has been investigated throughout the curing period and exposure to wet-dry cycles in 3.5% NaCl solution. During the curing, the high alkalinity of geopolymers prolongs the active state of both bare and galvanized steel. During the chloride exposure, fly ash geopolymers give the highest protection to reinforcements. The higher alkalinity of geopolymers compared to cement mortars seems to decrease the minimum free chloride threshold necessary to induce corrosion for galvanized steel, but it increases that for bare steel.

The Influence of Coating Thickness and Composition on the Corrosion Propagation Rates of Galvanized Rebar in Cracked Concrete

A study has been conducted of the chloride-induced corrosion behavior of four different batches of galvanized steel reinforcement embedded in sound and in cracked concrete. One batch of bars was of conventionally produced hot-dipped galvanized (HDG) steel, two were prototypes of continuously galvanized rebar, and the fourth was a hot-dipped bar with an experimental Zn-Al alloy coating. Carbon (black) steel bars were also tested for comparison purposes. The continuously galvanized process is aimed at producing a thinner, but more ductile coating than that formed by conventionally hot-dipped galvanizing process. Metallographic examination of the as-received galvanized bars showed a wide variation of the coating thickness around and along the bars, and the continuously galvanized coatings were consistently thinner than specified. All bars were cast in concrete which was subsequently cracked either parallel to or perpendicular to the embedded bars. Additional specimens were tested in the sound (non-cracked) concrete. All specimens were constantly exposed to a chloride brine for 64 weeks, and were electrochemically assessed bi-weekly during the exposure period. The electrochemical results and visual examination after autopsy showed that no active corrosion was initiated in either the galvanized or black rebar reinforced non-cracked concrete specimens. Therefore, the data in this project give no indication of initiation time or chloride threshold concentration for corrosion of these bars. On the other hand, in all cracked concrete specimens, corrosion initiated at the base of the crack and extended along or around the bars. In the cracked specimens, all galvanized bars exhibited lower current densities than the black bars, with the HDG being the lowest. Recommendations are given for appropriate interpretation of half-cell potentials of the galvanized bars investigated in terms of high or low probability of active corrosion.

Stainless and Galvanized Steel, Hydrophobic Admixture and Flexible Polymer-Cement Coating Compared in Increasing Durability of Reinforced Concrete Structures

The use of stainless or galvanized steel reinforcements, a hydrophobic admixture or a flexible polymer-cement coating were compared as methods to improve the corrosion resistance of sound or cracked reinforced concrete specimens exposed to chloride rich solutions. The results show that in full immersion condition, negligible corrosion rates were detected in all cracked specimens, except those treated with the flexible polymer-cement mortar as preventive method against corrosion and the hydrophobic concrete specimens. High corrosion rates were measured in all cracked specimens exposed to wet-dry cycles, except for those reinforced with stainless steel, those treated with the flexible polymer-cement coating as restorative method against reinforcement corrosion and for hydrophobic concrete specimens reinforced with galvanized steel reinforcements.

Resistivity Measurement of Backfill for Mechanically Stabilized Earth Walls

AbstractMechanically stabilized earth (MSE) walls often include galvanized steel strips as mechanical reinforcement within layers of specified backfill material. Galvanized steel reinforcement prov...

Performance of Galvanized Steel Reinforcement in Concrete in Sea and Dead Sea Water

Steel reinforcements of 8 mm diameter and 24 cm length were cut from steel and after pickling treatment of all specimens. Steel reinforcements then were galvanized by hot dipping method. The measured coating thickness by thickness gage meter of zinc coat was in the range 8 - 11 μm. Bare steel samples were also used for comparison reasons. Each steel bar was inserted in a middle of a plastic tube with 4.5 cm diameter into which concrete was cast. After proper curing, specimens were immersed into 3.5% NaCl and Dead Sea water separately. Electrochemical impedance spectroscopy measurements were performed at different time intervals. Results showed that galvanized steel was corrosion resistant in sea water, and Dead Sea water over the test period.

Pullout Resistance Factors for Steel MSE Reinforcements Embedded in Gravelly Backfill

Abstract This paper presents results from a laboratory program of 287 pullout tests of galvanized steel reinforcements used in the construction of mechanically stabilized earth (MSE) walls. Results focus on the evaluation of pullout resistance factors for ribbed steel strip and welded steel grid reinforcement embedded in gravelly backfill. This project used Texas Tech University’s large-scale MSE test box with dimensions of 3.6 × 3.6 × 1.2 m and an applied overburden capacity equivalent to 12 m of soil fill. The research design evaluated pullout resistance factors for both ribbed strip and welded grid reinforcements for a variety of independent variables, including overburden pressure, reinforcement length, grid bar size, and grid geometry including both transverse and longitudinal bar spacing. Appropriate statistical analyses were used to interpret the data within the context of published design guidance for inextensible MSE reinforcements. The results show that pullout resistance factors for both ribb...

Corrosion resistance of galvanized steel reinforcements in carbonated concrete: effect of wet–dry cycles in tap water and in chloride solution on the passivating layer

The effect of wet–dry cycles in tap water and in 3.5% NaCl solution on the passivating products of galvanized steel after concrete carbonation was investigated. The results show that carbonation destroys the passivating layer of calcium hydroxyzincate with the formation of the amorphous products ZnCO3 and Zn5(CO3)2(OH)6, which are also protective. The exposure to wet–dry cycles in tap water after concrete carbonation does not significantly increase the corrosion rate of the galvanized steel with respect to the values measured in non-carbonated concrete. On the contrary, the exposure to chloride solution after concrete carbonation leads to a marked decrease in the chloride threshold for galvanized steel corrosion with respect to that found in non-carbonated concrete.

Practical Model for Three-stage Corrosion Behaviour of Galvanized Steel Reinforcement in Soil

Practical Model for Three-stage Corrosion Behaviour of Galvanized Steel Reinforcement in Soil

Practical Model for Three-Stage Corrosion Behavior of Galvanized Steel Reinforcement in Soil

Failure of mechanically stabilized earth (MSE) walls attributed to the corrosion of galvanized steel in soil has raised concern on the adequacy of current design requirements. In this work, a numerical model was developed to calculate the corrosion rate of galvanized steel in soil at three different stages of corrosion by considering key soil corrosion parameters, such as resistivity, temperature, moisture content, pH, and oxygen availability. Results show that the proposed model is in agreement with widely accepted empirical models, and can be used for the service-life design and risk assessment of MSE walls and to determine the optimum zinc cover thickness.

Effect of de-icing salts on the corrosion performance of galvanized steel in sulphate contaminated soil

Failure of mechanically-stabilized earth (MSE) walls attributed to the corrosion of galvanized steel in soil has raised concern on the use of an appropriate type of the de-icing salt for the maintenance of the roads in the winter. This work presents the effect of commonly used de-icing salts such as sodium chloride, magnesium chloride, calcium chloride, and potassium acetate on the corrosion performance of the galvanized steel in sulphate contaminated soil. To achieve this goal, different electrochemical testing methods such as potentiodynamic polarization, Linear Polarization Resistance, and electrical impedance spectroscopy were used to determine the corrosion rate of galvanized steel reinforcement in sodium sulphate containing solution. Results showed that the presence of sulphate in the soil significantly increased the corrosion rates and, thus, it is important to consider the effect of sulphate in determining the type of de-icing salt. In sulphate-free solution, potassium acetate appeared to be the best option; while in the presence of sulphate, MgCl2 and CaCl2 had the lowest corrosion rate.

Corrosion behaviour of dual‐phase and galvanized steels in concrete

PurposeThe purpose of this paper is to present results of an evaluation of dual‐phase and galvanized steel reinforcements in corrosive environments.Design/methodology/approachLow carbon steels were intercritically annealed at 740°C followed by water quenching to obtain dual‐phase structures with 37 per cent volume fraction of martensite dispersed in ferrite matrix. Dual‐phase and galvanized steel rebars were embedded in concrete cubes and immersed in 5 per cent NaCl solution for up to 100 days. Corrosion rate, tensile and macro as well as microhardness tests were performed. The dual‐phase and galvanized zinc layers were observed under scanning electron microscopy (SEM).FindingsFrom all of the tests carried out it was found that dual‐phase steels exhibited better corrosion resistant properties and superior strength compared to galvanized steels.Originality/valueThe results reported show that dual‐phase steel can be a good candidate for reinforcement in concrete especially in aggressive and corrosive environments.

Comparison between surface and bulk hydrophobic treatment against corrosion of galvanized reinforcing steel in concrete

The effectiveness of bulk hydrophobic treatment against corrosion of galvanized steel reinforcement in concrete specimens with w/c = 0.45 and w/c = 0.75 was compared with that of surface treatment, even in the presence of cracks 0.5 and 1 mm wide in the concrete cover. In this case surface hydrophobic treatments were applied both before and after cracking as a preventive and a restorative method against reinforced concrete deterioration, respectively. The obtained results in terms of water absorption, electrochemical measurements, chlorides penetration, and visual observations carried out on reinforced concrete specimens during the exposure to wet–dry cycles in 10% NaCl solution showed that bulk hydrophobization is the most effective treatment in improving the corrosion resistance of galvanized steel reinforcements in concrete also in the presence of cracks. Surface hydrophobization is very effective just in the first few exposure cycles to the aggressive environment and when used as a restorative method which is able to cancel the deleterious effect of cracks only 0.5 mm wide.

Effect of concrete carbonation process on the passivating products of galvanized steel reinforcements

AbstractThe composition of passivating products on galvanized steel reinforcement in concrete during carbonation was studied. Cube‐shaped concrete specimens were manufactured with Portland 52.5 R cement and reinforced with hot‐dip galvanized steel sheets obtained from pure Zn and ZnSnBiNi alloy bath. The concrete specimens were exposed to air curing for 28 days and then to the carbonation chamber. Corrosion rate and potential measurements were performed both during the curing in air and exposure in a carbonation chamber. At defined periods of time, some concrete specimens were broken and the galvanized steel sheets were submitted to XRD, SEM observations and EDX analysis. The growth of the passivation products was evaluated by integrating the diffraction peaks. XRD analysis and SEM observations show that the layer of calcium hydroxyzincate (CaHZn), formed on the galvanized sheets during the air curing, is destroyed by the concrete carbonation process. However, potential measurements indicate that the galvanized steel always remains in the passive state. X‐ray diffractometry was not able to identify the new passivating product; EDX maps suggest the presence of zinc carbonates.

The effect of silane-based hydrophobic admixture on corrosion of galvanized reinforcing steel in concrete

Sound or deliberately pre-cracked concrete specimens, with 0.5 or 1 mm wide crack, were manufactured with water to cement ratios ( w/ c) of 0.45 and 0.75, both in the presence and in the absence of a silane admixture. The specimens were exposed to wet–dry cycles in a 10% NaCl aqueous solution. The results, in terms of electrochemical measurements, and visual and metallographic observations carried out on the galvanized steel reinforcement removed from the specimens, showed that the hydrophobic concrete is able to protect galvanized steel reinforcement from corrosion even in the presence of cracks in the concrete cover, especially when a high w/ c is used.