Electrogalvanized Steel Sheets Research Articles

Corrosion protection behaviour of electrogalvanised steel sheet by tetravalent vanadium ion

ABSTRACT The corrosion protection behaviour of electrogalvanised steel sheets (EG) by the tetravalent vanadium ion was investigated. Immersion of the bare EG in a NaCl solution revealed that the addition of vanadium(IV) oxide sulphate to the solution led to a transition of the open circuit potential to less noble and the formation of vanadium oxides on the EG surface. The oxide layer included not only vanadium(III) oxides but also a small amount of ZnO, indicating that Zn on the EG surface was oxidised while the vanadium(IV) species was reduced to the vanadium(III) species. The corrosion current density of the EG with the adhering vanadium(III) species was one order of magnitude smaller than that of the bare EG, clearly suggesting that zinc corrosion was reduced by suppressing the reduction reaction of dissolved oxygen. The vanadium(IV) species could be a candidate as a self-healing inhibitor for chromate-free coating technologies by controlling the coupling of Zn oxidation and vanadium(IV) reduction.

Enhancement of Steel Sandwich Sheet Adhesion Using Mechanical Interlocking Structures Formed by Electrochemical Etching.

Steel sandwich sheets (steel-polymer-steel), which are composed of lightweight polymers bonded on both sides with rigid steel sheets, have recently been developed as functional lightweight materials. In this study, a steel sandwich sheet (electrogalvanized (EG) steel sheet-polypropylene (PP)-EG steel sheet) with improved normal adhesion is fabricated without adhesives. Instead, adhesion is achieved via mechanical interlocking between the etched EG steel sheets and PP. Hierarchical structures were formed on the EG steel sheet surface by electrochemical etching to attain effective mechanical interlocking for improving normal adhesion without any adhesives. In the case of the EG steel sheet etched at 6 V for 7 s, a high fraction (∼35%) of holes (size: <1 μm2) with nanoscale scalloped structures was formed on the EG steel sheet surface. The normal adhesion test result of the fabricated steel sandwich sheet showed that the adhesion strength increased from virtually 0 (bare) to 559.6 kPa as a result of mechanical interlocking. The results of the focused ion beam-scanning electron microscopy and energy-dispersive spectrometry analyses confirmed the cohesive failure of PP resulting from the successful mechanical interlocking of PP with the holes formed on the etched EG steel sheet. To examine the effect of hierarchical structures on the normal adhesion of the steel sandwich sheet, finite element analysis was implemented.

Effect of Surface Texture of Steel Sheets on the Crystal Orientation Relationship between Zinc and Iron on Electrogalvanized Steel Sheets

Effect of Surface Texture of Steel Sheets on the Crystal Orientation Relationship between Zinc and Iron on Electrogalvanized Steel Sheets

Press formability of newly developed high lubricity hot-dip galvanized steel sheets

Surface modification technology was applied to hot-dip galvanized steel sheets (HDG) in order to improve their press formability. The frictional behavior and press formability of surface modified HDG were investigated in comparison with those of conventional HDG, conventional electrogalvanized steel sheets (EG) and pre-phosphate treated EG (EG pre-phos). Specimens of these coated mild steel sheets with various mechanical properties were used as test materials. The friction coefficient was measured by a flat sliding test, and press formability was evaluated by a deep drawing test and a stretch forming test. As a result, surface modified HDG showed a lower friction coefficient and higher press formability than conventional HDG and conventional EG. The friction coefficient and press formability of surface modified HDG were similar to those of EG pre-phos. In deep drawing, the inflow of material from the flange area to the cracking area becomes easier due to the lower friction coefficient of surface modified HDG, which leads to improvement of deep drawability. In stretch forming, the outflows of material from the sheet/punch contact area to the cracking area become easier due to the lower friction coefficient of surface modified HDG, leading to improvement of stretch formability. These results indicate that surface modified HDG is a promising material for automotive use.

Effect of Surface Textures of Steel Sheets on the Crystal Orientation Relationship between Zinc and Iron of Electrogalvanized Steel Sheets

Effect of Surface Textures of Steel Sheets on the Crystal Orientation Relationship between Zinc and Iron of Electrogalvanized Steel Sheets

Effect of Solution pH on Layered Double Hydroxide Formation on Electrogalvanized Steel Sheets

The effect of solution pH on layered double hydroxide (LDH) formation on electrogalvanized steel sheets (EG steel) was investigated in this study. EG steel with a Zn coating weight of 64 g/m2 was used as a substrate and was immersed in a 0.25 M Na2Al2O4-based solution having several pH values to form a Zn-Al-based LDH conversion coating. After rinsing and drying, corrosion resistance was evaluated by EIS. It was found that corrosion resistance increased with increasing pH up to pH 12.6. However, above this pH, corrosion resistance tended to display a sharp decrease. To understand this trend, the conversion coating was characterized by FT-IR, XRD and GDOES. The conversion coating was found to consist mainly of Zn2Al(OH)6(CO3)0.5·xH2O crystals (an LDH). The thickness of the conversion coating layer increased with increasing pH up to pH 12.4, but above this pH, its thickness tended to decrease due to the formation of ZnO. The reason for the dependence of corrosion resistance on solution pH is discussed from the viewpoints of the thickness and changes in the microstructure of the conversion coating layer, including its crystal size, density and uniformity, which could vary during the initial formation of ZnO at pH values above 12.6.

Corrosion Performance of Conversion Treatments for Electrogalvanised Steel Sheet

Fil: Di Sarli, Alejandro Ramon. Provincia de Buenos Aires. Gobernacion. Comision de Investigaciones Cientificas. Centro de Investigaciones en Tecnologia de Pinturas. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - La Plata. Centro de Investigaciones en Tecnologia de Pinturas; Argentina

Effect of NO3− Intercalation on Corrosion Resistance of Conversion Coated Zn-Al-CO3 LDHs on Electrogalvanized Steel

To modify the corrosion protection provided by conversion coated Zn-Al-CO3 layered double hydroxides (LDHs) on electrogalvanized steel sheets (EG steels), methods to intercalate NO3− during post treatment were explored and the effect of intercalation on corrosion resistance was evaluated. EG steels were immersed in a Na2Al2O4 based solution to form a Zn-Al-CO3 LDH conversion coating layer, and were then immersed in a NaNO3 methanol solvent to intercalate NO3−. After 2 h of immersion, it was found that NO3− had completely exchanged with the originally intercalated CO32− anions in the conversion coated Zn-Al-CO3 LDHs. Corrosion resistance measurements of the EG steel surfaces protected by the NO3− intercalated in the LDH layer were performed by a simple immersion test and a droplet test. When the samples were immersed in a large amount of 0.1 M NaCl, the corrosion resistance of the NO3− intercalated LDH layer was inferior to that of the control sample. In contrast, the samples that were exposed to a 100 μl droplet of 0.1 M NaCl displayed improved corrosion resistance. The difference in these results was attributed to the solubility of the LDH layer and the resulting effect on the release process of NO3− from the LDH layer.

Disk Laser Welding of Car Body Zinc Coated Steel Sheets / Spawanie Laserem Dyskowym Blach Ze Stali Karoseryjnej Ocynkowanej

Autogenous laser welding of 0.8 mm thick butt joints of car body electro-galvanized steel sheet DC04 was investigated. The Yb:YAG disk laser TruDisk 3302 with the beam spot diameter of 200 μm was used. The effect of laser welding parameters and technological conditions on weld shape, penetration depth, process stability, microstructure and mechanical performance was determined. It was found that the laser beam spot focused on the top surface of a butt joint tends to pass through the gap, especially in the low range of heat input and high welding speed. All test welds were welded at a keyhole mode, and the weld metal was free of porosity. Thus, the keyhole laser welding of zinc coated steel sheets in butt configuration provides excellent conditions to escape for zinc vapours, with no risk of porosity. Microstructure, microhardness and mechanical performance of the butt joints depend on laser welding conditions thus cooling rate and cooling times. The shortest cooling time t8/5 was calculated for 0.29 s.

Silane pretreatment of electrogalvanized steels: Effect on adhesive properties

The aim of this study was to evaluate the use of γ-methacriloxypropyltrimethoxysilane (MPS) to promote the adhesion of electrogalvanized steel sheets and threaded joints when an anaerobic adhesive is selected. The influence of the pH of the silane solution on the coupling agent properties of MPS coatings was evaluated preparing two silane aqueous solutions at 1% volume of silane and two different values of pH (4 and 6). Those coatings were characterized in terms of infrared spectroscopy (FTIR), scanning electronic microscopy (SEM), contact angle and surface energy. The influence of pretreatment conditions on the adhesive performance of steels was then evaluated both by shear tests from single lap adhesive joints and screw–nut bonds. Results show that the use of coatings hydrolyzed at pH 4 exhibit better adhesion behavior than those hydrolyzed at pH 6. The shear strength of anaerobic adhesive joints dramatically increases, showing a cohesive failure. This is related to the hydrolysis and condensation rates of silane solution and the stability of the metallic surface in contact with silane solution at the studied pH values.

Preparation and Characterization of Coating Solution Based on Waterborne Polyurethane Dispersion containing Fluorine for Primer on Electro Galvanized Steel Sheet

The purpose of this research was to synthesize fluorine modified waterborne polyurethane dispersion (F-WPU) by soap-free (internal emulsifier) emulsion polymerization techniques, to prepare coating solution based on fluorine modified waterborne polyurethane dispersion (F-WPU) and to compare the chemical and thermo-mechanical properties on the electrogalvanized steel sheet. Environmentally friendly F-WPU was prepared with a fluorinated polyol containing 60 wt% of fluorine. There are various ways of combining a wide variety of fluorinated polyols and diisocyanate to exhibit novel properties of waterborne polyurethane dispersion. Components of coating solution were largely divided into 4 kinds i.e., F-WPU, acrylic emulsion, silane coupling agent, and colloidal silicate. F-WPU coating solution on the electro-galvanized steel sheet showed excellent properties of corrosion resistance, alkali resistance and heat resistance, as compared to other coating solutions using a general waterborne resin. The F-WPU coating solution's reliable effects are possibly due to the fluorine atoms incorporated even in a small amount of F-WPU.

Influence of annealing temperatures on corrosion resistance of magnesium thin film-coated electro-galvanized steel

To improve the corrosion resistance of an electro-galvanized steel sheet, we deposited magnesium film on it using a vacuum evaporation method and annealed the films at 250–330°C. The zinc–magnesium alloy is consequently formed by diffusion of magnesium into the zinc coating. From the anodic polarization test in 3% NaCl solution, the films annealed at 270–290°C showed better corrosion resistance than others. In X-ray diffraction analysis, ZnMg 2 was detected throughout the temperature range, whereas Mg 2 Zn 11 and FeZn 13 were detected only in the film annealed at 310°C. The depth composition profile showed that the compositions of Mg at 270–290°C are evenly and deeply distributed in the film surface layer. These results demonstrate that 270–290°C is a proper temperature range to produce a layer of MgZn 2 intermetallic compound to act as a homogenous passive layer.

黒色薄膜有機被覆鋼板の皮膜特性に及ぼす黒色アゾ系金属錯塩染料の影響

Effects of azo-metal complex dyes on properties such as lightness value were investigated to examine a black thin organic coating (1-2 μm) on galvanized steel sheet for electrical appliances. This product consists of chromate coating and black thin organic coating on an electrogalvanized steel sheet or a Zn-Ni alloy plated steel sheet.(1) Solvent azo-metal complex dye, solvent azo dye, carbon black pigment, and aniline black pigment were surveyed. The L-values of the thin coatings containing solvent azo-metal complex dye with 30-40 wt% content were less than 15, whereas the L-value of coatings containing carbon black pigment were more than 23. The dye was considered to be solved uniformly, although carbon black pigment aggregated in the thin coatings. (2)The weathering resistance of the coating containing azo-metal complex dyes was superior to that of coatings containing azo dyes. (3)The black thin coating containing azo-metal complex dyes can provide both good corrosion resistance and spot weldability. (4) Results demonstrate that the black thin organic coating (1-2 μm), consisting of azo-metal complex dye and organic resin, can provide a good black appearance, weathering resistance, corrosion resistance, and spot weldability.

Underfilm corrosion of steel sheets observed by confocal 3D-XRF technique

A confocal micro-X-ray fluorescence (XRF) method with a vacuum chamber was used for investigation of underfilm corrosion that occurs on a painted steel sheet used for automotive applications. A painted steel sheet was prepared by applying electrodeposition coating onto an electro-galvanized steel sheet with a zinc phosphate conversion coating. The spatial resolution of the confocal micro-XRF was about 10.9 ?m at an energy of 17.4 keV. The phosphorus signal from the zinc phosphate layer was able to be observed nondestructively by measuring under the vacuum condition. Each layer of the painted steel sheet was observed from the depth profile analysis of the characteristic elements of each layer. The painted steel sheet was scratched to expose the substrate surface, and then the sheet was then immersed in a NaCl solution for 10 days. The in-depth elemental map of Ti of the corroded steel sheet revealed blister-type corrosion around the scratch. The in-depth elemental maps of Zn and P suggested that the zinc phosphate layer dissolved from the scratched part into the NaCl solution.

Effect of additives on the properties of phosphate conversion coating on electrogalvanized steel sheet

Ni2+ and Mn2+ ions have been added separately to the phosphate solution to minimize the porosity of the phosphate conversion coating on electrogalvanized steels. Results showed that the Ni2+ or Mn2+ in the solution reduced the grain size and porosity of the phosphate coating; thereby, the corrosion resistance was enhanced. However, Ni2+ and Mn2+ played a different role in the coating formation. Ni2+ in the solution was reduced by Zn to form Ni, which enhanced the dissolution of Zn to promote the nucleation of hopeite grains. Mn2+ in the solution facilitated the nucleation by increasing the impingement of reacting species.

Effect of Preadsorption of Organic Additives on the Appearance and Morphology of Electrogalvanized Steel Sheets

Effect of Preadsorption of Organic Additives on the Appearance and Morphology of Electrogalvanized Steel Sheets

Influence of friction parameters on springback and bend force in air bending of electrogalvanised steel sheet: an experimental study

This investigation analyses the effect of friction which is influenced by the parameters including type of lubricant, surface roughness of the sheet, die geometry and punch velocity on springback and bend force of electrogalvanised steel sheet in air-bending process experimentally. It is observed that the decrease in friction increases the springback and reduces the bend force. This effect is evident in case of high-viscosity lubricant, low surface roughness, larger die radius and higher punch velocity.

Prediction of bend force and bend angle in air bending of electrogalvanized steel using response surface methodology

This paper presents the development of predictive models for bend force and final bend angle (after springback) in air bending of electrogalvanized steel sheet employing response surface methodology. The models are developed based on five-level half factorial central composite design of experiments with strain hardening exponent, coating thickness, die opening, die radius, punch radius, punch travel, punch velocity as input parameters and bend force and final bend angle as responses. The results obtained from the models are in good accord with the experimental results. The effects of individual parameters and their interactions on the responses have also been analyzed in this study.

Influence of Annealing Temperatures on Corrosion Resistance of Magnesium Thin Film-Coated Electrogalvanized Steel

To improve the corrosion resistance of an electrogalvanized steel sheet, we deposited magnesium film on it using a vacuum evaporation method and annealed the films at 250-330℃. The zinc-magnesium alloy is consequently formed by diffusion of magnesium into the zinc coating. From the anodic polarization test in 3% NaCl solution, the films annealed at 270-310℃ showed better corrosion resistance than others. In Xray diffraction analysis, ZnMg₂ was detected through out the temperature range, whereas Mg₂Zn 11 and FeZn 13 were detected only in the film annealed at 310℃. The depth composition profile showed that the compositions of Mg at 270-290℃ are evenly and deeply distributed in the film surface layer. These results demonstrate that 270-290℃ is a proper temperature range to produce a layer of MgZn₂ intermetallic compound to act as a homogeneous passive layer.

Development of High Functional Black Resin Coated Electrogalvanized Steel Sheet for Digital TV Panel

Recently Digital TV industry has drastically been moving the illuminating system, which causes an obvious product change from PDP and LCD to LED model to provide high-definition image. Due to strong competition in the digital industry, TV manufacturers make a great efforts to reduce production cost by using low-priced materials such as steels instead of aluminum and plastic etc. In this paper we have developed a new low-priced electrogalvanized steel sheet, which has a black resin composite layer, to substitute conventional high-priced PCM steel and plastic mold for rear cover panel in the digital TV. The black resin composite was prepared by mechanical dispersion of the mixture solution that consists of high solid polyester resin, melamine hardener, black pigment, micronized silica paste, polyacrylate texturing particle and miscellaneous additives. The composite solution was coated on the steel sheet using roll coater followed by induction furnace curing and cooling. Although the coated layer has a half thickness compared to the conventional PCM steels having <TEX>$23{\mu}m$</TEX> thickness, it exhibits excellent quality for the usage of rear cover panel. The new steel sheet was applied to test products to get quality certification from worldwide electronic appliance customers. Detailed discussion provides in this paper including preparation of composite solution, roll coating technology, induction curing technology and quality evaluation from customers.