Galvanized Steel Research Articles

Hardness and corrosion resistance of Zn coatings on mild steel obtained by electrodeposition and hot-dip galvanization

The purpose of this work is a comparative study of the characteristics of the layers of Zn on a substrate of mild steel from two different processes (electrodeposition and galvanizing), and to review the progress that has been made in understanding the intermetallics phases’ effect on the corrosion behavior. The obtained Zn-containing film was investigated using diverse instrumental methodologies such as microhardness, X-ray diffraction, and potentiodynamic polarization measurements. This study allows the conclusion that the layers of Zn developed have: a homogeneous structure and good hardness. The corrosion test results showed an improvement in corrosion resistance for electrodeposition coatings compared with galvanizing coatings. XRD results identify that the electrodeposition and the galvanizing coatings have similar phases and the maximum hardness is obtained for the galvanizing process. Intermetallic phases were found to influence the corrosion behavior of mild steel. The results show that the size of Fe–Zn particles gradually decreases with the immersion time.

Rapid quantitative analysis of three elements (Al, Mg and Fe) in molten zinc based on laser-induced breakdown spectroscopy combined with machine learning algorithm

Hot-dip galvanizing represents one of the most cost-effective methods for the prevention of metal corrosion, and is therefore employed extensively across a range of fields. Carrying out the research and development of technology and devices for quantitative analysis of chemical elements in hot-dip galvanising process can provide theoretical basis and technical support for the efficiency of hot-dip galvanising process and reduction of energy consumption. A machine learning-assisted LIBS combined with a programmable logic controller (PLC) for simultaneous on-line/in-site monitoring of multiple elements in hot-dip galvanising solution (molten zinc) was developed in the current study. The LIBS spectral data of the on-site hot-dip galvanising solution was collected under optimised experimental conditions. In order to further reduce the influence of experimental noise on the analysis performance, the on-site LIBS spectral data were preprocessed and anomalous spectral data were screened based on normalisation and principal component analysis-mahalanobis distance (PCA-MD). On the basis of the optimised data, component prediction models for three key elements of on-site hot-dip galvanising solution were constructed. The storage and re-call of the model was achieved based on python combined with LabVIEW, thus real-time prediction of the on-site component content of hot-dip galvanising solution was achieved. The results show that the random forest model presents the best prediction results, in which the R2 is 0.9978 and the RMSE is 0.0013% for Al, the R2 is 0.9984 and the RMSE is 0.0011% for Mg, and the R2 is 0.9932 and the RMSE is 0.0001% for Fe. From the on-site analysis results of the constructed model, its MRE of Al, Mg and Fe is 0.0098, 0.0236, and 0.2102, respectively. In summary, the in-situ/on-line analysis system of hot-dip galvanising solution combined with machine learning constructed in this study shows excellent performance, which can satisfy the needs of hot-dip galvanising solution production site. This study is expected to provide theoretical basis and technical reference for quality control and process optimisation in other production sites in the metallurgical field.

Study of Flow and Zinc Dross Removal in Hot-Dip Galvanizing with Combined Traveling Magnetic Field

The removal of zinc dross, which continuously generates and partially floats on a molten zinc surface, has been a persistent challenge during hot-dip galvanizing. Herein, a three-dimensional mathematical model coupled with the electromagnetic field, flow field and air-knife jet flow was established to investigate the flow and zinc dross removal in a zinc pot. Two types of traveling magnetic field combined modes (Mode 1 and Mode 2) were compared. The surface dross removal efficiency was introduced to evaluate the ability of the zinc flow field to compel the movement of zinc dross. The research findings indicate that, in comparison to the influence of strip steel line speed, both the electromagnetic field and air-knife jet have a more pronounced effect on altering the flow characteristics of a molten zinc at surface. The dross removal efficiency for Mode 1 is much far superior to that of Mode 2. With an increase in the driving current, the dross removal efficiency increases while the excessive driving current cannot promote the dross removal efficiency significantly.

Comparative Study for Corrosion Resistance of Ferrous and Non-ferrous Pipes Immersed in Magnetized Water

This study aims to investigate the corrosion resistance of galvanized steel (GS) and AZ31 pipe materials immersed in a magnetized water treatment (MWT) applied river water source. The potentiodynamic corrosion test results showed that a better corrosion rate is obtained by the AZ31(corr.rate: 0.0442 mm/y) specimen than GS (corr.rate: 0.0764 mm/y) due to the passivation efficiency resulting from the calcite and MgO particles on the surface.

On the statistical assessment of the EN 1993-1-9 detail categories for hot dip galvanised steel

This paper provides the final developments regarding the fatigue life prediction of hot dip galvanised (HDG) steel details. The background information that has led to the definition of new S-N curves based on fatigue tests is firstly discussed, in accordance with the third draft revision of the EN 1993-1-9 and comparative guidelines. Using relevant statistical distributions and probability of survival levels, a statistical evaluation of all data retrieved from the literature is carried out. The two-parameter Weibull distribution, often used for reliability analysis in different areas of expertise, is also discussed. Finally, the overall impact of this assessment on the latest design rules from EN 1993-1-9 is discussed and guidance is given for an accurate determination of S-N curves for HDG steel details, based on the lessons learned.

Low-Carbon Steel Formed by DRECE Method with Hot-Dip Zinc Galvanizing and Potentiodynamic Polarization Tests to Study Its Corrosion Behavior

The use of low-carbon unalloyed steel with minimal silicon content is widespread in structural steel and automotive applications due to its ease of manipulation. The mechanical properties of this steel can be significantly enhanced through severe plastic deformation (SPD) techniques. Our study focuses on the practical benefits of the dual rolling equal channel extrusion (DRECE) method, which strengthens the steel and has implications for material hardness and the thickness of subsequently applied hot-dip zinc galvanizing. Furthermore, the steel’s corrosion potential and current are investigated as a function of material hardness and thickness. The findings show a 20% increase in hardness HV 30 after the first run through the forming machine, with an additional 10% increase after the second run. Subsequent galvanizing leads to a further 1–12% increase in HV 30 value. Notably, the DRECE hardening demonstrates no statistically significant effect on the corrosion potential and current; however, the impact of galvanizing is as anticipated.

Corrosion protection performance of stretched graphene-modified cold-sprayed zinc coating for steel rebar

The cold-sprayed zinc technology exhibits unique advantages in the field of metal corrosion prevention due to its environmental friendliness and convenient construction. However, compared to hot-dip galvanizing, there is still a necessity to improve its corrosion resistance. Graphene as a filler material, effectively strengthens the anticorrosive properties of the coating. Nevertheless, the resistance of graphene-modified cold-sprayed zinc coating to chloride ion induced metal corrosion remains unknown. In this study, cold-sprayed zinc coating and graphene-modified zinc coating were employed to steel rebar that was subjected to different levels of tensile stress. The passivation and de-passivation process of the stretched zinc-coated rebar in the simulated concrete pore solution were investigated with electrochemical tests and microscopic analyses. The research findings reveal that compared with ordinary cold-sprayed zinc coating, graphene-modified coating can significantly improve the coating resistance and reduce the corrosion rate of rebar under different levels of tensile stress attributed to the high surface area of graphene. However, due to the discontinuity between zinc powders induced by graphene, a complete passivation film cannot form on the surface of graphene-modified zinc coating, which resulted in a lower resistance against chloride ion induced de-passivation. This study indicates that graphene-modified cold-sprayed zinc-coating is not fit for marine environment.

Enhanced corrosion protection of steel strip through advanced Zn–Mg alloy coatings manufactured by Continuous Physical Vapor Deposition: A review

The growing global consensus on the “carbon peak and neutrality” has focused on high-strength steel, highlighting its critical role in enhancing energy efficiency, reducing emissions in the steel industry, and reducing the weight of automobiles. Traditional Electro-Galvanizing (EG) and Hot-Dip Galvanizing (HDG) technologies face challenges in meeting the surface protection demands of these applications. This limitation is evident with the development of Zn–Mg coated strip steel, which offers high corrosion resistance. Continuous Physical Vapor Deposition (CPVD) effectively addresses these issues in a sealed vacuum environment, drawing significant attention in the strip coating industry owing to its superior surface quality, diverse material options, and environmental advantages. This article reviews the latest advancements and current status of Zn–Mg alloy coatings prepared using the CPVD technology. It discusses the typical thermal evaporation process used in CPVD, traces the development history of CPVD coatings on strip steel, and examines the microstructure, corrosion resistance, and adhesion performance evolution mechanisms of Zn–Mg alloy coatings. By designing multilayer structures, adjusting the Mg composition, and implementing controllable heat treatments, the overall performance of the coatings is enhanced. This study also comprehensively analyzes the feasibility of applying multilayer, highly corrosion-resistant Zn–Mg coatings. Additionally, it identifies the main challenges in applying CPVD technology to Zn–Mg coatings on strip steel, such as the large-scale, stable, and low-cost mass production of typical processes and controlling the void content at multilayer interfaces. Finally, future research directions are anticipated, underscoring the potentially significant impact of further alloying and computer simulations in advancing steel surface treatments.

Environmental prospects for galvanizing steel technologies

The article discusses the main technologies for applying zinc coatings, which make it possible to protect steel products from corrosion and thereby reduce the harmful impact on the environment. The technological features of hot, galvanic, thermal diffusion, cold and gas-thermal galvanizing are described. A comparative analysis of the considered galvanizing technologies was carried out from the point of view of their harmful effects on the environment and human health. The analysis made it possible to establish that hot-dip galvanizing is applicable to protect steel strips and wires, which has minimal impact on the environment, but the surface preparation processes for it cause significant harm to the environment and human health. Electroplating production is one of the most dangerous sources of environmental pollution, due to the fact that both in the surface preparation process and during the coating itself, reagents and electrolytes are used that have a harmful effect on both the environment and human health. Thermal diffusion, cold and gas-thermal galvanizing during surface preparation allows mechanical cleaning using abrasive materials, which significantly increases the environmental friendliness of these methods. Thermal diffusion and gas-thermal galvanizing are by far the most environmentally friendly processes and allow the application of corrosion-resistant coatings to products of complex shapes. The use of wire in gas-thermal galvanizing makes it possible to increase the economic efficiency of the process compared to powder technologies. The equipment used for thermal spraying is universal and can be used to apply various protective coatings, as well as restore worn parts. The impact of this galvanizing method on the environment is minimal and is today one of the most effective and promising methods of protecting steel products from corrosion.

Interpreting the main effects on the efficiency and morphology for establishing a procedure of electrodepositing Zn from purified chloride SPL solutions

Potentiodynamic and galvanostatic experiments have been used to investigate the electrodeposition of Zn and to develop a reliable recovery method from a purified spent pickling liquor (SPL) of hot dip galvanization. The main bjective was to find the suitable conditions to deposit high-grade Zn from the purified ZnCl2–HCl–NaCl solution in a conventional electrowinning cell holding the stationary electrolyte. The effects of pH (1.5–4.5) in and Zn concentration (30–150 g/dm3) in the stationary electrolytes were studied first by the potentiodynamic method to reveal the major characteristics of the cathodic process and to give reference for further practical examinations by the galvanostatic technique. The electrowinning experiments pointed out the effects of these major parameters, beside other practical factors, like apparent current density (c.d.) and additional NaCl concentration. The long-term galvanostatic experiments proved that the current efficiency (c.e.) increases significantly as the pH and the Zn concentration are increased. A c.e. of ~ 99% can be reached with an electrolyte of pH ~ 5, Zn concentration ~ 50 g/dm3 applying a c.d. in the 300–600 A/m2 range. Increasing the Zn concentration could considerably improve also the deposit morphology. The addition of NaCl can practically improve the c.e. if the Zn concentration is at least around 50 g/dm3. In contrast, this improvement is largely off-set by the negative effects of strong H2 evolution at low (e.g. < 10 g/dm3) Zn concentrations. Extremely high Cl− ion concentrations, however, inhibit the cathodic reaction by stronger chloro-complex formation. In this case the intensive H+ reduction causes hydroxide precipitation.

On the coupling instability of a gas jet impinging on a liquid film

We investigate the dynamics of a gas jet impinging perpendicular to a thin liquid film dragged by a rising vertical substrate. This configuration is relevant to the jet-wiping process in hot-dip galvanization and it is unstable. Previous studies analysed the dynamics of the instability in the case of liquids with low Kapitza numbers (highly viscous liquids), more amenable to experimental and numerical investigations. This work extends the previous investigations by focusing on the wiping at much higher Kapitza numbers, which are more relevant to the galvanizing process. The simulations are carried out by combining volume of fluid and large-eddy simulations, and the dynamics of the gas–liquid interaction is analysed using extended multiscale proper orthogonal decomposition. The simulations allowed for analysing the jet-wiping instability in new flow conditions. Despite the largely different conditions, the results show that the interaction between the gas jet and the liquid film is qualitatively similar, featuring two-dimensional waves in the liquid correlated with oscillations and deflections of the gas jet in all cases. The wave characteristics (e.g. frequency and propagation speed) scale remarkably well using the Shkadov-like scaling based on the liquid, suggesting a dominant role of the liquid film in the coupling, and potentially enabling extrapolation of the results to a broader range of wiping conditions. Finally, we use the numerical results to discuss the limitations of liquid-film models, which constitute currently the only possible approach to study the jet-wiping process in industrial conditions.

Synergistic photocatalytic degradation of ciprofloxacin under natural sunlight using hot dip galvanization and medical incineration waste residues

To improve the photodegradation capacity, for the first time, a simple yet efficient photocatalyst was prepared by solely employing hot dip galvanization waste (GW) and fly ash (FA) disposed from medical waste incinerators. Impressively, the as-synthesized photocatalyst (GW-FA) in the ratio 3:1 displayed an outstanding ciprofloxacin degradation efficiency of 98.3% under natural sunlight within 60 min and possessed superior reusability. Herein, adjusting the amount of GW evidenced effective tuning of the electronic band structure and increased active sites. Detailed microscopic morphology, chemical structure, magnetic, and optical properties of GW-FA were studied by UV-DRS, FESEM-EDX, HRTEM, XRD, XPS, ESR, VSM, and AFM, which confirmed the successful fabrication of GW-FA and their outstanding ability to reduce the recombination rate. Besides, the effects of crucial experimental parameters (concentration, pH, and photocatalyst loading) on ciprofloxacin degradation were examined using RSM-BBD. Further, OH• was manifested to be the main active species for the photodegradation of ciprofloxacin. Eventually, GC-MS analysis was employed to deduce plausible photodegradation pathways, and ICP-AES analysis proved that the concentration of leached heavy metals was lower than that of the standard limits for irrigation water. This work establishes a new route for effectively reutilizing waste generated from medical waste incinerators and galvanization industries as a photocatalyst, which otherwise would be disposed in landfills.

Effect of manufacturing-induced microscopic surface defects on crack initiation and fatigue mechanisms in hot-dip galvanized steel

When designing against fatigue, the surface condition of steel is of utmost importance. Since hot-dip galvanizing is a surface treatment primarily aimed at preventing corrosion, it is critical to assess its influence on the fatigue properties of steel. Given the challenges in producing large structural galvanized steel without imperfections, it is crucial to understand the influence of manufacturing-induced microscopic surface defects on crack initiation and fatigue mechanisms in hot-dip galvanized steel. In this study, to gain such insights, tension-tension fatigue testing was conducted on hot-dip galvanized steel, followed by a detailed analysis of the crack initiation sites to determine any correlation with manufacturing-induced microscopic surface defects. It was observed that under low-cycle fatigue, pre-existing surface defects did not appear to have influenced fatigue mechanisms. However, under high-cycle fatigue, crack initiation sites exhibited evidence of pre-existing manufacturing induced defects which were significantly smaller than the total crack initiation area. This indicates that the defects could not immediately penetrate the substrate but expanded within the layer and only penetrated the substrate after reaching a critical size. Therefore, it is discovered that while manufacturing-induced defects may be challenging to eradicate entirely, those below a threshold size may not immediately evolve into a stable fatigue crack. Hence, if manufacturing induced defects are kept below a critical size, they may not significantly influence the transition of stage I crack into a stable stage II crack.

High-Temperature Zn-5Al Hot Dip Galvanizing of Reinforcement Steel

High-Temperature Zn-5Al Hot Dip Galvanizing of Reinforcement Steel

Comparative Analysis of Coatings Applied for Anti-Corrosion Protection of Public Transport Vehicles' Structural Parts.

The conducted research focused on anti-corrosion systems applied for the protection of structural parts used in public transport vehicles. Detailed tests were carried out on samples taken from the brackets supporting the doors of a public transport bus. This work includes the results of the chemical analysis of the composition of snow-mud samples taken from the selected bus route and the results of laboratory tests performed on samples with various anti-corrosion coatings. Four types of samples made of S235JR steel with a zinc coating deposited by thermo-diffusion, electroplating, hot-dip zinc galvanization, and the cataphoresis method were tested. Both non-destructive tests-NDTs (the measurement of coating thickness and roughness, microscopic observations)-and destructive tests-DTs (scratch tests, salt chamber tests)-were performed. The conducted tests proved that the most effective method is the use of anti-corrosive hot-dip zinc coating.

Achieving energy efficiency and sustainability in galvanization process: A case study on Indian tower manufacturing industry

Abstract There is a significant gap between India’s energy production and its demand. Dependency on energy imports to meet the energy requirement affects the economic growth &amp; overall development. The manufacturing sector consumes a substantial portion of the country’s energy but also holds considerable potential for reducing consumption. This paper presents a case study on an Indian tower manufacturing industry, aiming to achieve energy efficiency and sustainability in the galvanization process through the application of the statistical tool Design of Experiments (DOE). By systematic implementation of 22 factorial model of DOE, the study identified that the excessive zinc coating thickness is the major cause of energy consumption in hot-dip batch galvanization process (HDBGP). It was found that average LPG consumption is minimized at moderate coating thickness. Applying DOE resulted in a 38.67% reduction in LPG consumption when the zinc coating thickness was maintained at a moderate level in HDBGP. DOE provides a systematic mechanism based on experimental data to identify potential causes of problems and offers statistical validation of results. This research focuses on creating an energy-efficient production system and demonstrates the practical application of statistical tools and techniques to achieve sustainable competitive advantages. Highlights Experimental work using the Design of Experiments tool identified excessive zinc coating thickness as the primary cause of high energy consumption in the hot-dip batch galvanization process. Validation of optimized parameters showed that average energy consumption is minimized at moderate coating thickness, resulting in a 38.67% reduction in energy usage. Design of experiments tool provides a systematic mechanism based on experimental data to identify potential causes of problems and offers successful validation of results. Discussion While the significant reduction in LPG consumption enhances energy efficiency and sustainability, excess reduction in coating thickness may compromise the quality and durability of galvanized products, potentially leading to higher long-term costs for maintenance and replacements. Additionally, the focus on statistical tools like DOE alone could divert attention from exploring alternative potential energy-saving technologies and methods that might offer greater benefits. Therefore, it is also essential to consider the broader implications and potential limitations of various approaches in the quest for sustainability and competitive advantage suitable for the existing manufacturing setups. Graphical abstract

Recovery and utilization of zinc dross for sacrificial anode cathodic protection of steel structures

Zinc dross is highly zinc-rich industrial waste produced during galvanization of steel. It is a byproduct of the reaction between molten zinc and loose iron particles in a molten zinc bath. Generally, 10–20% of galvanized zinc is converted into zinc dross. This work proposes a unique way of recycling of dross into a high value sustainable resource material leading to development of sacrificial anode used in cathodic protection of steel. The electrochemical behavior was studied in 3.5 wt% NaCl solution. The anode performance test was performed as per the standard DNV-RP-B401 in an artificial seawater solution. The performance parameters, (closed circuit potential (CCP), anode efficiency, and consumption rate) of the recovered zinc anode from dross, are close to the commercial zinc anodes. It satisfies the required anode criteria. Hence, the recovered zinc anode from dross could be used as a sacrificial anode for the cathodic protection of steel structures.

Experimental Investigation Of The Gas-Liquid Interface And Flow Field Dynamics Near The Contact Line In An Immersing Flat Surface

Dynamic wetting is fundamental to many coating processes. In hot dip galvanization, an unstable contact line can generate wetting defects and air entrainment in the coating, limiting the quality of the final product. While the literature focuses mainly on capillary-viscous flows, which are amenable to analytical treatment, some configurations, such as dip coating, operate in inertia-dominated conditions. This work presents an extensive and unprecedented experimental characterization of the interface and contact line dynamics on a surface entering a liquid bath in inertia-dominated conditions using laser-induced fluorescence (LIF). Moreover, we complement the analysis with particle tracking velocimetry (PTV) underneath the gas-liquid interface to study the interaction between the liquid flow and the free surface. Proper orthogonal decomposition (POD) of the interface displacement is presented and analyzed in combination with the velocity field dynamics, enhanced by physics-constrained Radial Basis Functions (RBFs).

Corrosion inhibition of steel rebar in chloride-contaminated concrete pore solution: Ecofriendly glutamic acid inhibitor and its synergy with galvanized coating

In this study, we explore the effectiveness of glutamic acid as corrosion inhibitor for protecting steel rebars within a concrete pore solution contaminated with chloride (CCCPS) along with its synergy with galvanized coating are investigated. The study is defined in two phases: (a) examining the inhibition efficiency (%IE) of glutamic acid at various concentrations of 0.25, 0.50, 0.75, and 1 g/L using a combination of experimental and theoretical methods, and (b) evaluating its synergistic effect with Zn present in the galvanized coating. In the first phase, various electrochemical tests and theoretical investigations are employed. The electrochemical examinations consistently demonstrated that at a concentration of 1 g/L, the maximum %IE reaches ∼ 80 %. Langmuir adsorption isotherm fitting effectively describes the relationship between inhibitor concentration and its coverage percentage. Thermodynamic data indicate the adsorption of these inhibitors on the steel surface involves both physical and chemical adsorptions with a ΔG°ads (standard free energy of adsorption) of around –23.5 kJ/mol. Moreover, the activation energy for corrosion of steel rebar increases from 55.8 kJ/mol for the blank CCCPS to 78.3 kJ/mol for the inhibited CCCPS. Molecular dynamics simulations validate the binding of glutamic acid molecules to the surface of the steel, primarily through nitrogen atoms orientation towards d-orbitals of steel substrate. In the second phase, the carbon steel rebar underwent hot-dip galvanization, resulting in a galvanized coating with a thickness of approximately 36 µm. The synergistic effect of glutamic acid at its optimum concentration (0.75 g/L) was investigated with comparison of the corrosion behavior of three samples: bare steel, galvanized steel, and scratched galvanized steel in simulated CCCPS with and without the inhibitor. Results indicate that the presence of the inhibitor significantly enhances the %IE, up to 99 %, for scratched galvanized steel. FESEM/EDS analysis further reveals a substantially lower volume of corrosion products in the scratched area of the latter sample compared to its counterpart in the inhibitor-free solution. Furthermore, as indicated by the findings from X-ray photoelectron spectroscopy (XPS), the interactions between the N and Fe atoms, acting as donors and acceptors, respectively, hold significant importance in the chemisorption process.

Fatigue resistance and reliability assessment of hot dip galvanised plates with welded transversal stiffeners

This paper investigates the effect of galvanisation on the fatigue strength of plates with welded transversal stiffeners. A series of 50 fatigue tests were carried out on welded details made of S355 structural steel. For comparison purposes, tests were performed on both hot dip galvanised (HDG) and uncoated joints. In addition, the influence of different cutting methods on the fatigue life was addressed. The experimental fatigue data was analysed, using different statistical methods commonly used in survival analysis. Both the normal distribution function, following the EN1993-1-9 approach, and the two-parameter Weibull distribution function, were considered. For the latter, different methodologies were employed to evaluate its key parameters. Finally, it was concluded that the resulting Wöhler curve for the HDG plates with welded transversal stiffeners matches the fatigue detail category80 of EN1993-1-9. The results of this study were used to propose new revisions of EN 1993-1-9, to extend its scope to galvanised steel details.