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Non-ferrous metals
Published in Ash Ahmed, John Sturges, Materials Science in Construction: An Introduction, 2014
Zinc is a relatively soft metal with a low melting temperature and a density of 7,100 kg m–3. In construction zinc is used to a small extent for roofing and cladding, but its main importance in construction is as corrosion protection for steel as galvanising. In galvanised steels, a thin coating of zinc is applied to steel items to protect them against wet corrosion. This process is cheap, and it significantly extends the life of steel items in service, i.e. it improves the durability of steel. This is especially economical in comparison to stainless steel, which is expensive due to the high price of chromium (more than 10 per cent of this metal is required for stainless steel). Thus, for large-scale production galvanising is always preferred; hence, nearly all structural steel beams used in construction are galvanised. Other non-construction applications of zinc include automotive parts (door handles and grilles), padlocks and office equipment.
Opto-Mechanical Characteristics of Materials
Published in Paul Yoder, Daniel Vukobratovich, Opto-Mechanical Systems Design, 2017
Cadmium, chromium, and nickel platings are frequently added to other metals to protect their surfaces from corrosion. Ferrous metals can be galvanized by dipping in molten zinc, by heating and tumbling in zinc dust (the sherardizing process), by electrolytic deposition, or by flame spraying with atomized powdered metal (metalizing). Cadmium applied by electroplating is also used on iron parts, but its durability may be impaired by the presence of sulfur in the atmosphere. Carbon steels and the Invars are frequently protected by chrome plating. Usually, a nickel undercoat is applied before coating with chromium. The chromium layer coating is hard and so serves as a protection against wear and abrasion.
Manufacturing Products
Published in Roger Timings, Basic Manufacturing, 2006
In this process, steel components and assemblies are cleaned physically and chemically and immersed in molten zinc to give them a protective coating. A small amount of aluminium is usually added to the melt in order to give the finish an attractive ‘bright’ appearance. Although the zinc coating is much more resistant to corrosion than steel, nevertheless it will very slowly corrode away in the presence of acid rain and in marine environments. Since in protecting the steel, the zinc slowly corrodes away it is said to be sacrificial. To retard this corrosion even further, galvanized goods may also be painted to protect the zinc finish.
Monitoring of weld defects of visual sensing assisted GMAW process with galvanized steel
Published in Materials and Manufacturing Processes, 2021
Guohong Ma, Haitao Yuan, Lesheng Yu, Yinshui He
At present, with the introduction of intelligence manufacturing and sensor technology, welding automation is a significant part in the growth of modern industry. It is extensively applied in the fields of large splicing parts such as aerospace, ships, automobiles, etc.[1–4] To achieve the research and growth of welding automation, intelligence and flexibility, it should satisfy at least four requirements: initialize weld position, weld seam tracking, weld quality control and weld defect detection.[5,6] Galvanized steel, because of its excellent corrosion resistance, compatibility, and mechanical properties, is widely used in automobile body and building structures.[7,8] However, galvanized steel needs additional welding current and time, internal force than ordinary carbon steel, because the zinc metal coating on the surface of galvanized steel will produce a special shunting effect, which makes welding parameters difficult to control,[9] and the zinc metal on the surface coating of the galvanized steel sheet will evaporate and melt. Meanwhile, GMAW is a complex process with poor stability, easy to produce spatter, and unstable heat output,[10,11] which will affect the quality of the weld, so weld defects are usually unavoidable. In fact, if experienced workers locate and evaluate weld defects manually, this inspection method may lead to high cost, low efficiency, subjectivity and even bias, because the detection results of welding defects basically depend on actual experiences and knowledge accumulation of workers, visual accuracy, and image quality.
Corrosion protection behaviour of electrogalvanised steel sheet by tetravalent vanadium ion
Published in Transactions of the IMF, 2023
Takeshi Matsuda, Shinichi Furuya, Rie Kaneko, Koji Fushimi
Galvanised steel sheets are widely used in automobiles, electrical machinery and buildings because the zinc coating has the effect of suppressing the corrosion of the steel substrate. Among these products, electrogalvanised steel sheets (EG) are used in electrical machinery such as electrical appliances and office automation equipment due to the appearance of a uniform metallic lustre. It is important to protect the zinc coating from corrosion because corrosion products such as zinc oxide deteriorate the appearance of electrical machinery. Chromate coatings composed of chromium(III) oxides and a small amount of chromium(VI) had been applied to prevent the corrosion of EG.1–4 Chromate coatings are characterised by a high barrier property to corrosive species and an adhesion property with metal substrates because chromium(III) oxides can be polymerised and combined with the metal substrate.1,5–9 A self-healing ability is also a distinctive feature, as the reduction reaction of chromium(VI) ions forms a polymerised coating consisting of chromium(III) oxide in areas where the coating is defective or damaged.2,8–10 Thus, chromate coatings can achieve superior corrosion protection with a thin coating layer, maintaining the metal-like appearance of the substrate. However, strict regulations have been applied to the use of certain heavy metals such as Cd, Pb, Hg and Cr(VI) due to their high toxicities, as seen, for example, in the ‘Restriction of Hazardous Substances (RoHS) Directive’ enforced in Europe from 2003.11 Thus, alternative coating systems are required for corrosion protection of EG.
Effect of elemental additions on hot-dipping galvanization behavior
Published in Cogent Engineering, 2023
Murtadha A. Jabbar, Mohammed Y. Yousif, Nuha H. Jasim
Hot-dip galvanization begins with thoroughly cleaning the steel surface to remove any oil, grease, or other contaminants that may interfere with the zinc’s bonding. At approximately 450°C, the steel is immersed in liquid zinc. In steel, zinc reacts with iron to produce intermetallic layers that prevent corrosion. Galvanizing steel is an effective and cost-effective method of protecting it from corrosion because it gives it a long-lasting, low-maintenance coating. The excellent corrosion resistance and the high strength-to-weight ratio of galvanized steel make it ideal for construction, automotive, and manufacturing applications.