Galvanized Steel Research Articles

Effect of prior copper-coating on the microstructural development and corrosion behavior of hot-dip galvanized Mn containing high strength steel sheet

In the present investigation, the role of copper (Cu) pre-coating has been studied for the development of good quality corrosion-resistant hot-dip galvanized (GI) coating on high strength CMn steel sheets. The Cu pre-coated GI steel has a more pronounced texture coefficient (TC) of the preferred high atomically dense (0002) crystal plane of Zn coating as compared to the GI steel without pre-coating. It has been observed that the GI coating with Cu pre-coating shows excellent surface quality in comparison to the GI coating without Cu pre-coating, which exhibits many bare spots on the final coating. Further, the Cu pre-coated GI steel has revealed the development of a continuous iron aluminide (FeAl) intermetallic interfacial layer that has a uniform distribution of dense and equiaxed FeAl crystals at its interface with the substrate. It can also be noticed that the Cu pre-coated GI steel has a superior corrosion resistance when compared to the GI steel without pre-coating. This is ascribed to the Cu pre-coated GI steel forming a continuous compact interfacial layer with the maximum atomically dense (0002) crystal plane and a high-quality defect-free coating.

Numerical Simulation of Traditional and Technological Zinc‐Based Coatings: Part I

Herein, the bending behavior of a hot‐rolled hyper‐sandelin steel subjected to hot‐dip galvanizing (HDG) is numerically simulated. Two coating types are analyzed, that is, a pure zinc coating and a zinc‐based coating with 3% Sn addition by weight. It is experimentally observed that the tin addition influences the thickness of each intermetallic phase and increases the ductility of the intermetallic phases. Therefore, the key of the numerical simulation is to assume suitable constitutive laws to phase layers, by considering that only few mechanical parameters are available in the literature. Such an approach has shown quite satisfactory results and it can be promising as a numerical tool to be used by HDG industry, being quite simple but quite accurate to estimate flexural strength and damage of Zn‐based coated steels.

Impact of pipe material on the wall reaction coefficients and its application in the rehabilitation of water supply system of San Pedro Nexapa, State of Mexico

Abstract One of the major challenges faced by water companies around the world is the high level of chlorine losses in distribution networks. This paper presents an experimental study to examine chlorine loss in different types of pipe materials and select the ones with low chlorine demand for the rehabilitation of the water distribution network of San Pedro Nexapa, State of Mexico. The materials investigated include: polyvinyl chloride (PVC), galvanized steel (GS), polypropylene (PP) and high-density polyethylene (HDPE). A 24-h chlorine consumption study was performed in a simulated water distribution network to assess the impact of wall reaction coefficient on chlorine decay. Four sets of independent pipe loops of 50 mm in diameter and 12 m in length were used. Two different scenarios were considered based on different initial chlorine concentration (1.21 mg/L and 1.60 mg/L). Samples were collected at each loop at two-hour intervals and physicochemical analyses were conducted. Results from the experimental distribution network showed that the wall coefficient values for GS, HDPE, PP and PVC were 0.165 h−1, 0.059 h−1, 0.043 h−1 and 0.026 h−1, respectively. Experimental results showed that wall reaction coefficient values depend on initial chlorine concentration and the characteristics of pipe material. The rate of free chlorine decay was found to be faster in steel pipe and slower in the plastic pipes. Based on its having the lowest chlorine demand compared with the other pipes, PVC pipe would be selected to rehabilitate Nexapa water distribution network, State of Mexico. The wall coefficients from the experimental study were incorporated into EPANET through four simulation runs to predict chorine decay of San Pedro Nexapa water distribution network, State of Mexico. In the PVC and PP pipes higher residual chlorine concentrations were observed that ranged from 0.30 to 0.90 mg/L and 0.50 to 0.95 mg/L, respectively. This study is important for utilities to operate their system effectively and protect public health.

Emissivity of hot-dip galvanized surfaces in future development of EN 1993-1-2

PurposeThis study aims to propose a new design value, based on experimental and numerical studies, for surface emissivity of zinc hot-dip galvanized members exposed to fire.Design/methodology/approachThe paper sums up experiments, used specimens and also shows results. Four experiments were performed in a horizontal furnace and one test in a fire compartment of the experimental building. Several tests were carried out for determination of the surface emissivity of galvanized steel structures in fire. The experimental and numerical studies were used for preparation of new generation of the structural steel fire standard Eurocode EN 1993-1-2:2025.FindingsHot-dip galvanizing is one of the most widely used processes for corrosion protection of steel products. The new design value for surface emissivity of zinc hot-dip galvanized members exposed to fire is determined using experimental results as 0.35. The value is proposed for next generation of EN 1993-1-2:2025. If hot-dip galvanization additionally can contribute beneficially to the fire resistance of unprotected steel members, it would be a huge economic advantage.Originality/valueExperimental studies in the past years have indicated the influence of hot-dip galvanizing on the heating of steel members. This study suggests 50% reduction of the surface emissivity of a carbon steel member. This amendment will be incorporated in future versions of Eurocodes 3 and 4 and has already been implemented in some fire design tools for steel members in order to consider the beneficial contribution of hot-dip galvanized for fire-resistance requirements of less than 60 min.

Electro-galvanization of zinc and zinc-nickel onto mild steel for improved corrosion resistance

Pure zinc was electroplated on mild steel sample at specific potential and current density from sulphate bath and its characterization was done by various techniques. Corrosion rate of coating was found using potentio-dynamic polarization technique. Corrosion rate of coating was improved using alloyed coating (zinc-nickel).The main objective was to replace hot-dip galvanization technique with electro-galvanization so as to reduce thickness of coating and also to do away with problem of heat affected zone arising in hot dip galvanization, further enhancing the corrosion resistance of electro-galvanized coating by using alloying elements.Pure zinc was deposited on mild steel via electrodeposition technique at potential and current density values of −1.45 V, −1.55 V, −76 mA/cm2, −97 mA/cm2 respectively. Thickness of coating was measured using surface profilometer. SEM images and XRD data were taken and analysed and finally corrosion rate was calculated using Tafel extrapolation. Further zinc-nickel was electrodeposited on mild steel sample at −1.45 V and −1.55 V and corrosion rate of coating was compared with pure zinc coating.It was observed that for pure zinc coating as the deposition potential increases from −1.45 V to −1.55 V, the corrosion resistance is enhanced. With addition of alloying elements such as nickel the corrosion resistance of coating was slightly increased and also coarse grain structure was obtained when SEM images were compared.

Electroplating of Zn at different current densities onto mild steel for improved corrosion resistance

The main objective was to replace hot-dip galvanization technique with electro-galvanization so as to reduce thickness of coating and also to do away with problem of heat affected zone arising in hot dip galvanization, further enhancing the corrosion resistance of electro-galvanized coating by using alloying elements.Pure Zinc was electrodeposited on mild steel (MS) sample at specific current densities i.e. at −50, −150, −250 mA/cm2 from sulphate bath and its characterization was done by various techniques. The deposition current/ potential obtained by a systematic cyclic voltammetry study. Corrosion rate of coating was found using potentio-dynamic polarization technique and corrosion mechanism was obtain by Electrochemical Impedance Spectroscopy (EIS) analysis. Thickness of coating was measured using surface profilometer and was found to be in the range of 13 µm to 29 µm. Scanning electron microscopy (SEM) images and X-ray diffraction (XRD) data were taken and analyzed and finally corrosion rate was calculated using tafel extrapolation. Best corrosion result was found at −150 mA/cm2 current density.The corrosion resistance of coating was slightly increased and also coarse grain structure was obtained when SEM images were compared.

Combination of discrete and finite element method to simulate damage in galvanised steel

In the present paper, the bending behaviour of a hot-rolled hyper-sandelin steel, subjected to hot-dip galvanizing (HDG), is numerically simulated in Ansys LS-DYNA environment by combining the Discrete Element Method (DEM) with Finite Element Method (FEM). The coating examined is composed by different layers: the layers with a ductile behaviour are modelled by using elastoplastic constitutive laws for the FEs, whereas the layers with a quasi-brittle behaviour are simulated by using DEs. Such an approach shows quite satisfactory results and it can be promising as a numerical tool to be used by HDG industry, being accurate to estimate the damage of galvanized steel.

Anion exchange separations to produce a suitable electrolyte for the electrodeposition of pure zinc

Anion exchange separations have been devised to purify model solutions of the usual pickling liquor (SPL) obtained from hot dip galvanization to produce a suitable ZnCl2 electrolyte for electrodepositing pure Zn. The method was based on the established anion-exchange distribution functions in chloride media. Both the simple batch and the more accurate chromatographic methods of separation were examined. The loaded solutions contained Zn, Fe, Mn, Ni and Pb of different concentrations with 1.8 - 2 M NaCl or HCl as the background. The resin bed primarily retained Zn while divalent Fe, Mn and Ni were removed in the loading and the continued rinsing steps with the mobile phase at the initial level of Cl- ion concentration. The elution of Zn was carried out by a significantly reduced Cl- ion concentration. The preliminary reduction of the iron to its divalent state was found of utmost importance. The only difficulty arises from the separation of Pb, which has an equilibrium distribution function comparable to the anion exchange of Zn, however in Europe this minor impurity should not be present at disturbing levels. Kinetic examination of the batch process revealed that Zn sorption is virtually complete within 20 minutes, however despite the low distribution coefficients, some 10 % of iron is also sorbed. Almost 90 % of the retained iron could be in the Fe(III) state caused by aerial oxidation. It was also found that the elution of Zn in the batch technique was not possible by just lowering the Cl- ion concentration. Therefore, the chromatographic method is the only possible way if only chloride media are to be applied.

Переработка металлической фракции изгари хлорированием

The growth in the capacity of enterprises for hot-dip galvanizing of steel products has led to the formation of large volumes of waste, which accumulate and store, occupying large areas. Further use and processing of ash is constrained by the increased content of Pb, Fe, Cu and other impurities in it, as well as the lack of rational processing technology. In this work, based on the thermodynamic analysis of the reactions of interaction of impurity metals with chlorinating reagents (CaCl2, NH4Cl), the possibility of obtaining pure zinc in the process of melting the metal component of the ash is shown. It has been established that the values ​​of the Gibbs free energy (∆G°T) of the reactions of interaction of metal-impurities with ammonium chloride in the temperature range 400...550°С are four times higher than the values ​​of ∆G°T of the reactions of interaction of metal-impurities with calcium chloride. It is shown that the use of NH4Cl as a chlorinating reagent destroys the zinc oxide film covering the surface of small drops of metallic zinc and creates favorable conditions for their enlargement. This increases the yield of zinc to the liquid metal. The influence of the consumption of CaCl2 and NH4Cl on the sublimation of lead and iron from a metallic liquid bath of zinc in the form of chlorides has been studied. It was found that when the metal component is melted together with a consumption of 2% NH4Cl based on the weight of the initial sample, the minimum content of lead and iron in liquid zinc is achieved: 0.06% Pb and 0.01% Fe. The optimal technological parameters for melting the metal component of the ash together with NH4Cl were determined: temperature of experiments 450°С; melting time 60 min; consumption of NH4Cl - 2.0% of the weight of the original sample.

Enhancement of Tribological Performance in Li2tio3/Zro2 Composite Coating Prepared by Industrial Hot-Dip Galvanization Process

Enhancement of Tribological Performance in Li2tio3/Zro2 Composite Coating Prepared by Industrial Hot-Dip Galvanization Process

A heat balance model of zinc pot and its application

In this paper, the problem of stripe temperature at the entrance of the zinc pot is addressed in a novel way. Based on in-depth analysis of thermal features of hot-dip galvanization, a generalized heat-balance mode has been established that has wider adaptivity within the production lines. The relationship between the pot load, the galvanization load and the productivity has been re-characterized by introducing a new concept of line-area ratio. Subsequently, the stripe temperature can be estimated based on the model. The effectiveness of the proposed model has been verified by real-time application to the production lines with temperature estimation error within ± 3 °C. As such, effective temperature compensation can be implemented that significantly improves the galvanization quality.

Fatigue strength of hot-dip galvanized S960 cut edges and longitudinal welds

Experimental fatigue test series were conducted for component sized hot-dip galvanized (HDG) S960 cut edges and longitudinal welds. Scanning electron microscopy (SEM) was used to identify and characterize the crack initiation location and the effects of local chemical composition. Micro-scale liquid metal embrittlement in the vicinity of the cut surface was found to slightly reduce fatigue performance of tested laser cut, machined and welded specimens. The use of ultra-high-strength steels in the HDG condition is discussed and fatigue strength guidelines are proposed for the tested details.

Enhancing adhesion and anti-corrosion performance of hot-dip galvanized steels by sandblasting/phosphating co-treatment

The substations outdoor steel structures employed in aggressive marine environments can accelerate corrosion damage and cause incredible degradation of performance. Hot-dip galvanizing and organic coating dual-coated anticorrosion system is currently the most effective and efficient protection strategy. In present paper, sandblasting and phosphating technique were applied to the surface of zinc plating, the effect of various grit-blasting and phosphating technology conditions on the adhesion performance and corrosion resistance of duplex-coated system were systematically investigated. Results revealed that the bonding strength of the duplex coating after grit-blasting and phosphating pretreatment was 3.25 and 2.71 times higher than that of the untreated, respectively. In particular, sandblasting and phosphating coprocessing of duplex coating could furtherly improve the adhesion behavior and corrosion resistance, which mainly due to their synergistic effect. Sandblasting can rough the surface of galvanized coating and generate many pits and scratches. Thus, phosphating can form more needle-like zinc phosphate crystals in those positions, anchoring and pinning firmly the interface between galvanized coating and organic coating. Meanwhile, the phosphating film still acted as an anti-corrosion physical barrier to hinder the intrusion of corrosive medium and protect galvanized steels from storage rust before painting for a long time.

Black Anodic ZnO Film on Galvanized Steel Using Mixed Electrolyte of Ca(OH)2–KOH–NaOH

Black Anodic ZnO Film on Galvanized Steel Using Mixed Electrolyte of Ca(OH)2–KOH–NaOH

Monitoring of the condition and development of package systems for continuous hot-dip galvanizing of thin-sheet steel products

The paper discusses the technical features of modern package systems for continuous hot-dip galvanizing, a distinctive feature of which is a module layout that not only ensures the timely replacement of breaking down individual sections of a continuous line, but also allows to enter/withdraw the equipment in the manufacturing process as needed, which makes it possible to produce the strip with different types of coatings on the same machine. The analysis of the main types of alloys used for hot-dip galvanizing has shown that coatings of all four types of alloys are used for products undergoing cold deformation and cold stamping. It is advisable to coat multi-phase steels for cold deformation with coatings based on Zn, ZnFe or ZnAl. The ability to deform and weldability of products is higher, the greater the thickness of the coating. Consequently, coatings based on ZnFe and ZnAl alloys with a thickness of 18.0 microns and 19.3 microns are suitable for deformable and welded products. To reduce the cost of galvanized metal by reducing the consumption of expensive zinc, one-sided galvanizing of steel sheet is promising. The chemical compositions and applications of the four most widespread zinc-based coatings, namely zinc, zinc-iron, zinc-aluminum and aluminum-zinc, are considered. It is indicated that on modern hot-dip galvanizing lines, the coating on the strip is applied from two sides. However, technologies for unilateral application of zinc coating on a steel strip are currently being developed, the use of which will reduce the consumption of expensive zinc and, consequently, the cost of finished products. Some effective methods and devices for one-sided galvanizing are presented and described

Processing Dross from Hot-Dip Galvanizing by Chlorination Roasting

Dross from hot-dip galvanizing is an important source of pure zinc ingots and zinc oxide for use as mineral additives in animal and poultry feed. Thermodynamic calculations have shown the possibility of solving the issue of dross processing by roasting using CaCl2 and NH4Cl. The influence of the consumption of chlorinating reagents, the roasting temperature on the degree of sublimation of Pb, Fe, Ni, Cu and Cd has been investigated. It has been shown that the best results are achieved when roasting the dross with the simultaneous use of CaCl2 and NH4Cl in amounts of 6 and 15% by weight of the feed material. The optimal roasting parameters were established: T = 1000 °C, duration—60 min, air flow—0.1 L/min. Recovered pure zinc oxide composition (%) was: 0.05 Pb, 0.15 Fe, 0.06 Ni, 0.003 Cu and 0.001 Cd. The degree of sublimation of copper, nickel and iron chlorides was ~75%, with lead and cadmium at 90–98% of their initial amount in the dross.

Study on Cracking Behavior of High‐Strength Steels by Liquid Zinc‐Induced Embrittlement

Although Zn‐coatings have enhanced corrosion resistance of steels, Zn‐induced liquid metal embrittlement (LME) is susceptible during hot forming. Prolonging the annealing time before hot forming availably prevents LME by eliminating the liquid phase. Herein, the austenitization process window by systematically investigating the effects of annealing time on the mechanical properties of high‐strength (press‐hardened 22MnB5, dual‐phase DP980, and quenching‐partitioning QP1180) steels and LME cracking behaviors for corresponding galvanized (GI) steels are optimized. The results support LME undermines the mechanical properties of all GI steels, while the effecting of the coating for the 22MnB5 is few. Calculation of phase diagram (CALPHAD) is used to evaluate the influence of annealing time on the ductility of the steels. Furthermore, the formation mechanism of LME cracks during the austenitization of galvanized QP1180 is studied. At the initial stage, the interfacial Fe–Al inhibition layer is destabilized. The cracks initiated on the surface of γ‐Fe are induced by the synergistic effect of strain and penetration of liquid Zn. The results of transmission electron microscopy (TEM) indicate that Fe‐Zn compound (Γ‐Fe3Zn10) is created and carbon enriches at the interfaces between the infiltrating Zn and γ‐Fe substrates at the LME crack tips.

Accelerated Corrosion Tests in Quality Labels for Powder Coatings on Galvanized Steel-Comparison of Requirements and Experimental Evaluation.

Powder coatings are widely applied for corrosion protection of steel, aluminum, and hot dip galvanized steel in a variety of corrosive environments. Powder coatings are subjected to a number of strict laboratory tests to determine their mechanical properties, corrosion resistance, and color stability. Among European quality certificates for powder coatings applied to galvanized steel, the most commonly recognized are GSB-ST and Qualisteelcoat certificates, which also refer to the EN 13438 standard. Certificates of quality for powder coatings are constantly updated according to the latest research results and experience of specialists operating in the field of corrosion protection. This paper presents an experimental evaluation of how the required length of selected accelerated corrosion tests can affect the final assessment of powder coatings. On the example of two powder painting systems: polyester as well as based on epoxy and polyester resins, the paper presents the influence of the time of accelerated corrosion tests: ISO 6270, ISO 9227 (Neutral Salt Spray and Acetic Acid Salt Spray), and ISO 3231 on the protective properties of the coatings. The results of damage assessment according to ISO 4628 have been correlated with the requirements of particular quality specifications. Additionally, based on FTIR (Fourier Transform Infrared Spectroscopy) and EIS (Electrochemical Impedance Spectroscopy) analyses, the influence of the applied corrosion tests on the degradation degree of the coatings studied has been presented. The paper aims to present a tests for those powder coating systems applied to facilities for which the main requirement is corrosion resistance rather than aesthetics.

Design of direct-formed square and rectangular hollow section beams

A complementary experimental study showed that the flexural member design rules in the North American steel design standards (AISC 360–16 and CSA S16-19) can be excessively conservative for direct-formed regular- and high-strength steel square and rectangular hollow sections (hereinafter collectively referred to as RHS). It was also found that post-production hot-dip galvanizing can further improve member flexural behaviours through effective reduction of cold-forming-induced residual stresses. In this study, the experimental results of 22 full-scale beam tests from the complementary experimental study are used to validate non-linear finite element (FE) models. The FE models are developed using previously measured stress-strain relationships, residual stresses, and geometric imperfections. A subsequent parametric study including 788 beam models is performed to cover extended ranges of cross-sectional dimensions. The applicability of the existing slenderness limits and flexural design formulae are examined using the experimental and numerical data. The results justify the use of less stringent slenderness limits and higher design curves for direct-formed regular- and high-strength RHS beams (untreated and galvanized). Modifications to the existing design rules are proposed. Based on reliability analyses, the modified approaches are proven accurate and provide adequate safety margins.

Corrosion Characterization at Surface and Subsurface of Iron-Based Buried Water Pipelines.

Water pipe surface deterioration is the result of continuous electrochemical reactions attacking the surface due to the interaction of the pipe surface with environments through the time function. The study presents corrosion characterization at the surface and sub-surface of damaged ductile iron pipe (DIP) and galvanized steel (GS) pipes which served for more than 40 and 20 years, respectively. The samples were obtained from Addis Ababa city water distribution system for the analysis of corrosion morphology patterns at different surface layers. Mountains 8.2 surface analysis software was utilized based on the ISO 25178-2 watershed segmentation method to investigate corrosion features of damaged pipe surface and to evaluate maximum pit depth, area, and volume in-situ condition. Based on the analysis maximum values of pit depth, area and volume were 380 m, 4000 m2, and 200,000 m3, respectively, after 25% loss of the original 8 mm thickness of DIP. Similarly, the pit depth of the GS pipe was 390 whereas the maximum pit area and volume are 4000 m2 and 16,000 m3, respectively. In addition, characterizations of new pipes were evaluated to study microstructures by using an optical microscope (OM), and a scanning electron microscope (SEM) was used to analyze corrosion morphologies. Based on the SEM analysis, cracks were observed at the sub-surface layer of the pipes. The results show that uniform corrosion attacked the external pipe surface whereas pitting corrosion damaged the subsurface of pipes. The output of this study will be utilized by water suppliers and industries to investigate corrosion phenomena at any damage stage.