The recorded history of galvanizing goes back to 1742 when a French chemist named Malouin, in a presentation to the French Royal Academy, described a method of coating iron by dipping it in molten zinc.
In 1836, Sorel, another French chemist, obtained a patent for a means of coating iron with zinc, after first cleaning it with 9% sulfuric acid and fluxing it with ammonium chloride. A British patent for a similar process was granted in 1837. By 1850, the British galvanizing industry was using 10,000 tons of zinc a year for the protection of steel.
Galvanizing is found in almost every major application and industry where iron or mild steel is used. The utilities, chemical process, pulp and paper, automotive, and transportation industries, to name just a few, historically have made extensive use of galvanizing for corrosion control. They continue to do so today. For over 150 years, hot-dip galvanizing has had a proven history of commercial success as a method of corrosion protection in myriad applications worldwide.
Though the process may vary slightly from plant to plant, the fundamental steps in the galvanizing process are:
Soil & grease removal - A hot alkaline solution removes dirt, oil, grease, shop oil, and soluble markings. Pickling - Dilute solutions of either hydrochloric or sulfuric acid remove surface rust and mill scale to provide a chemically clean metallic surface.
Fluxing - Steel is immersed in liquid flux (usually a zinc ammonium chloride solution) to remove oxides and to prevent oxidation prior to dipping into the molten zinc bath. In the dry galvanizing process, the item is separately dipped in a liquid flux bath, removed, allowed to dry, and then galvanized. In the wet galvanizing process, the flux floats atop the molten zinc and the item passes through the flux immediately prior to galvanizing.
Galvanizing - The article is immersed in a bath of molten zinc at between 815-850 F (435-455 C). During galvanizing, the zinc metallurgically bonds to the steel, creating a series of highly abrasion-resistant zinc-iron alloy layers, commonly topped by a layer of impact-resistant pure zinc.
Finishing - After the steel is withdrawn from the galvanizing bath, excess zinc is removed by draining, vibrating or - for small items - centrifuging. The galvanized item is then air-cooled or quenched in liquid.
Inspection - Coating-thickness and surface-condition inspections complete the process. The galvanizing process has existed for more than 250 years and has been a mainstay of North American industry since the 1890s.
Galvanizing primary component is zinc. This vital substance is silvery blue-gray in color and makes up an estimated 0.004% of the earths crust and ranks 25th in order of abundance. It is essential for the growth and development of almost all life: Between 1.4 and 2.3 grams of zinc are found in the average adult, and the World Health Organization has recommended a daily intake of 15 milligrams. Numerous consumer products including cold remedies, sunscreens, diaper creams, and nutritional supplements contain beneficial amounts of zinc, primarily in the form of zinc oxide.
Even though galvanized steel is blue-gray, it also is green. The zinc and galvanizing industries work to promote sustainable development by enhancing zinc's contribution to society and ensuring that its production and use are in harmony with the natural environment and the needs of society, now and in the future.
Zinc, as it is used in galvanizing, is a healthy metal, completely recyclable. The energy used to smelt zinc is inversely related to the amount of zinc recycled. Galvanizing delivers incredible value in terms of protecting our infrastructure. Less steel is consumed and fewer raw materials are needed because galvanizing makes bridges, roads, buildings, etc, last longer. Over time, galvanizing helps maintain steel fabrications' structural integrity: galvanized structures are safer. Additionally, because galvanized steel requires no maintenance for decades, its use in public construction is an efficient use of our taxes. Selecting galvanized steel for private projects makes a significant contribution to a company's profitability.
In 1836, Sorel, another French chemist, obtained a patent for a means of coating iron with zinc, after first cleaning it with 9% sulfuric acid and fluxing it with ammonium chloride. A British patent for a similar process was granted in 1837. By 1850, the British galvanizing industry was using 10,000 tons of zinc a year for the protection of steel.
Galvanizing is found in almost every major application and industry where iron or mild steel is used. The utilities, chemical process, pulp and paper, automotive, and transportation industries, to name just a few, historically have made extensive use of galvanizing for corrosion control. They continue to do so today. For over 150 years, hot-dip galvanizing has had a proven history of commercial success as a method of corrosion protection in myriad applications worldwide.
HDG Process
Though the process may vary slightly from plant to plant, the fundamental steps in the galvanizing process are:
Soil & grease removal - A hot alkaline solution removes dirt, oil, grease, shop oil, and soluble markings. Pickling - Dilute solutions of either hydrochloric or sulfuric acid remove surface rust and mill scale to provide a chemically clean metallic surface.
Fluxing - Steel is immersed in liquid flux (usually a zinc ammonium chloride solution) to remove oxides and to prevent oxidation prior to dipping into the molten zinc bath. In the dry galvanizing process, the item is separately dipped in a liquid flux bath, removed, allowed to dry, and then galvanized. In the wet galvanizing process, the flux floats atop the molten zinc and the item passes through the flux immediately prior to galvanizing.
Galvanizing - The article is immersed in a bath of molten zinc at between 815-850 F (435-455 C). During galvanizing, the zinc metallurgically bonds to the steel, creating a series of highly abrasion-resistant zinc-iron alloy layers, commonly topped by a layer of impact-resistant pure zinc.
Finishing - After the steel is withdrawn from the galvanizing bath, excess zinc is removed by draining, vibrating or - for small items - centrifuging. The galvanized item is then air-cooled or quenched in liquid.
Inspection - Coating-thickness and surface-condition inspections complete the process. The galvanizing process has existed for more than 250 years and has been a mainstay of North American industry since the 1890s.
Galvanizing primary component is zinc. This vital substance is silvery blue-gray in color and makes up an estimated 0.004% of the earths crust and ranks 25th in order of abundance. It is essential for the growth and development of almost all life: Between 1.4 and 2.3 grams of zinc are found in the average adult, and the World Health Organization has recommended a daily intake of 15 milligrams. Numerous consumer products including cold remedies, sunscreens, diaper creams, and nutritional supplements contain beneficial amounts of zinc, primarily in the form of zinc oxide.
Even though galvanized steel is blue-gray, it also is green. The zinc and galvanizing industries work to promote sustainable development by enhancing zinc's contribution to society and ensuring that its production and use are in harmony with the natural environment and the needs of society, now and in the future.
Zinc, as it is used in galvanizing, is a healthy metal, completely recyclable. The energy used to smelt zinc is inversely related to the amount of zinc recycled. Galvanizing delivers incredible value in terms of protecting our infrastructure. Less steel is consumed and fewer raw materials are needed because galvanizing makes bridges, roads, buildings, etc, last longer. Over time, galvanizing helps maintain steel fabrications' structural integrity: galvanized structures are safer. Additionally, because galvanized steel requires no maintenance for decades, its use in public construction is an efficient use of our taxes. Selecting galvanized steel for private projects makes a significant contribution to a company's profitability.
