Papers by Keyword: Galvanized Steel

Abstract: Welding technologies are constantly evolving, and their applicability is expanding, considering also the construction domain. Steel structures benefit from the advances in welding technologies due to the use of thin gauge steel sheets which can now be connected at high quality and automatically. The resistance of the connection between the thin steel sheets is crucial for the durability and safety of a structure made of built-up thin-walled cold-formed steel elements. Generally, self-drilling screws or bolts are used for the connection between thin-walled elements, but the quantity of time and manpower necessary for a large number of connections demands an improved solution. Conventional welding techniques are unsuitable for joining thin sheets, ranging from 0.4 to 1.0 mm to thicker ones measuring 1.0 to 3.5 mm. This article compares the results of an experimental investigation into lap joints connected by spot welding and MIG brazing with the design code provisions. The study examines single-lap joints in steel sheets of 0.8, 1.0, 1.2, 1.5, 2.0 and 2.5 mm thickness, connected using these welding technologies. The results obtained are then compared with analytical relations and processed according to EN 1990. Depending on the thickness of the connected sheets, spot welding can lead to two failure modes: button pull-out fracture and interfacial fracture. MIG brazing, a welding technology that deposits material below the melting point of the base material, is known for its advantages, such as low energy consumption, spatter-free operation, high welding speed, and compatibility with thin sheet metals. However, its application in the structural engineering of cold-formed elements lacks documentation. In the study, the MIG brazed specimens failed in the heat-affected zone of the connection. The results indicate the dependence of the spot weld lap joint resistance on the connected sheets' thickness, while the resistance of the MIG brazed lap joints is influenced by the minimum thickness of the connected steel sheet. The study aims to demonstrate the feasibility of the proposed solutions, evaluate their performance, and establish the limits of their applicability. A statistical interpretation of the results highlights the precision and reliability of joint resistance.

Abstract: Mortar-based composites are an emerging technology for the repair and strengthening of reinforced concrete and masonry structures. In most cases, the effectiveness of the retrofitting work relies on the substrate-to-composite bond capacity but in some applications, connectors are also used to prevent debonding and improve the performance of the retrofitted structure. Indeed, the use of connectors is recommended by design guidelines and suppliers are required to test them for acceptance. The paper presents a laboratory investigation on steel reinforced grout connectors, made by rolling ultra-high tensile strength steel textiles, comprising either galvanized or stainless-steel micro cords. Tensile tests were first carried out for mechanical characterization. Pull-out tests were then performed on connectors installed in holes drilled in wall panels and injected with either cement or lime mortars. Concrete, tuff masonry, brickwork and limestone masonry were used as substrate materials. Test results are commented to analyze the effect of textile rolling on tensile response, of textile and matrix properties on pull-out strength and failure mode, as well as to highlight their significance for design purposes.

Abstract: Microorganisms can initiate, accelerate, and/or inhibit corrosion processes through several different ways, including modification of the localized environment at the metal/solution interface causing pitting attack. In this work, the effect of pH on Pseudomonas growth was investigated in understanding the biodeterioration manganese steel rod due to bacteria attack. This study focused on identifying the effect of pH on the corrosion of galvanized steel. In artificial seawater containing Pseudomonas Aeruginosa. Galvanized steels were exposed to the medium for 7 days at 37°C at pH ranging from 5.0 to 9.0. Roles of different metallurgical, chemical and microbiological features on the surface will be reviewed to interpret this phenomenon. The results confirmed that the pits formed in this case are attributed to the Pseudomonas Aeruginosa sp under microbial corrosion.

Abstract: Corrosion behavior of three carbon steels with increasing galvanized coating thickness of 5.6, 8.4 and 19.2 μm named as T₁, T₂ and T₃, respectively, was studied by immersion test, potentiodynamic polarization and electrochemical impedance spectroscopy in freely aerated 3.5% NaCl solution. The major phase in the corrosion product of all the samples after immersion test was found to be zincite, as determined by X-Ray Diffraction and Fourier Transform Infrared Spectroscopy techniques. The corrosion product on sample T₁was well adhered and was compact in most regions. Samples T₂ and T₃ showed porous and non-adherent growth of corrosion product. Corrosion rates were found to increase with increasing coating thickness. The impedance provided by the coating as well as the substrate was the highest for the sample with thinnest coating (T₁). The early exposure of the underlying steel in sample T₁ resulted in higher corrosion resistance, which was probably due to the combined effect of zinc corrosion products and Fe-Zn alloy layer. Higher amount of protective γ-FeOOH as well as compact corrosion product could have also improved the corrosion resistance of sample T₁. Although the average uniform corrosion resistance was higher for T₁, the localized pitting corrosion was also observed, probably due to the thin galvanized layer.

Abstract: Nitrogen-containing heterocyclic dicationic compounds with antioxidant properties have been synthesized and characterized by NMR spectroscopy. Their corrosion inhibiting behavior for zinc and steel protection have been studied by electrochemical polarization methods to assess the potential suitability of those compounds in hybrid galvanic zinc protective coatings. The individual assessment for corrosion inhibiting activity will facilitate the shortlisting of eligible candidates, help to avoid potential incompatibilities of ingredients, and reduce times in the process of designing hybrid coatings for corrosion protection. This study has found that the compounds have significant corrosion protecting effect on steel and zinc and those molecules were shortlisted for our future studies on galvanic hybrid coating of steel.

Abstract: Zink (Zn) in galvanized steel has a positive effect on improving the properties of the dissimilar metals weld between aluminum alloy and galvanized steel. Its distribution is important to be evaluated. The aim of this work is to investigate the effect of rotation speed and dwell time on the Zn distribution of the friction-stir-spot-welded (FSSW) dissimilar metals between aluminum alloy and galvanized steel. FSSW was subjected to 3 mm thick of Aluminum and 1 mm thick of galvanized steel with a plunge depth of 2.7 mm and a penetration rate of 0.9 mm/s. High strength steel (HSS) with a hardness of 70 HRC and a diameter of 12 mm was used as FSSW tool. Tool rotation was varied at 1000 rpm, 1200 rpm, 1600 rpm, and 2000 rpm while dwell time was varied of 3 s, 5 s, and 7 s. A Scanning Electron Microscope (SEM) was performed to reveal the Zn distribution after cross-sectioning, polishing, and etching. During the FSSW process, the heat was generated, Zn softened, and carried away by the materials flow due to tool rotation. Both the rotation speed and the dwell time played a role in increasing the distance and the amount of Zn flow in the welded zone. FSSW process in dissimilar metals between aluminum and galvanized steel formed the unique pattern of Zn distribution.

Abstract: During transportation, long-term storage and operation metal products are exposed to atmospheric corrosion that leads to billions of losses every year. The urgency of the problem being investigated is due to the fact that export of metal products is mainly carried out by sea through regions with humid tropical climate. The search for new packaging materials is a significant trend in corrosion control. The research of effective corrosion inhibitors that are capable to protect all kinds of metals, such as steel, zinc, copper, aluminum, is actually carried out, as well as the process of development of getting the packaging materials containing the corrosion inhibitors. The purpose of this paper was a research of anticorrosive properties of experimental packaging papers under increased humidity and in the presence of chloride of sodium. In this paper the test conditions which, correspond to the handling conditions of steel products through the zones with tropical climate, were simulated. The studies research found out that the experimental patented corrosion inhibitors do not take protective effect on galvanized steel. The generated corrosion products are incoherent, weakly coupled with metal and easily fall off (crumble), that results in metal loss.

Abstract: Cerium conversion coatings were obtained by immersing hot-dip galvanized steel (HDG) sheets in a cerous nitrate solution. The surface morphologies were observed with scanning electron microscopy. The composition of the coating were determined with X-ray energy dispersive spectrometer and X-ray photoelectron spectroscopy. The results showed that the modified cerium conversion coating grows more quickly than that of common cerium conversion coating. Potentiodynamic polarization and electrochemical impedance spectroscopy measurements revealed that the corrosion resistance of the modified cerium conversion coating was superior to that of common cerium conversion coating and was comparable to that of the conventional chromate passivation coating.

Abstract: The corrosion behavior of galvanized steel in corrosive media of simulated concrete pore solution (SPS) with and without NaCl has been studied for applying it to porcelain insulator’s pins in high-voltage alternating current (HVAC) transmission line. It was found that zinc coating of galvanized steel was corroded increasingly for the first 3 days corrosion test in SPS mixed with NaCl solution. After that the passive layer was formed on the surface of galvanized coating and consequently, the corrosion rate was dramatically decreased nearly five times of initial corrosion rate after 21 days. In this experiment, the investigations have been performed by SEM, optical microscope and visual observation. The results show that this compact and well adherence passive layer can be effectively hindered the corrosion process.

Abstract: This work aims to evaluate the influence of the alkoxy precursor concentration on the morphological and electrochemical characteristics of the chemical conversion layer formed on a galvanized steel surface. Different films were obtained by the dip coating method varying precursor concentrations in 2, 5 and 10%. According to the SEM and EIS results the corrosion resistance property increases for higher GPTMS precursor concentrations.