Hot Dip Galvanization Process – An Overview

By Author: Bluesteel Services
Total Articles: 25
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Three basic steps in hot dip galvanization process are surface preparation, galvanizing and inspection. Surface preparation determines the durability of coating typically involving caustic cleaning, pickling and fluxing. In caustic cleaning, organic contaminants are removed, while fluxing eliminates oxides. Read on to know more.

Galvanization is an effective, low-cost method to improve the durability of steel, which is coated in a thin layer of zinc to promote the corrosion resistance of the product. The process involves cleaning incoming substrate with an alkaline detergent, annealing, coating with molten zinc and leveling tension on both lines. The product is heat-treated after coating to prepare it for painting. Procurers can also get done ink printing and chem-treatment done on steel.

Hot dip galvanizing process, which is preferred by the industries, consists of three basic steps – surface preparation, galvanizing and inspection.

Surface preparation is the critical first step that determines the durability of coating. Zinc simply won’t stay on a steel surface that is not clean. Surface preparation ...
... typically involves caustic cleaning, pickling and fluxing.

In caustic cleaning, the steel is dipped in a hot alkali solution for removal of organic contaminants such as grease, oil, paint markings and dirt. Vinyl, epoxies, welding slag and asphalt is removed by mechanical means like grit blasting and sand blasting. It is then put in a rinsing tank. Next step is pickling when the product is dipped in a dilute solution of hydrochloric acid, which cleans scale and rust from the surface. Now, it is dipped in a second rinsing tank.

The final step for preparation is fluxing, which eliminates oxides and prevents further oxides from forming on the metal surface prior to galvanization. It promotes bonding of zinc to the steel surface. The product is then pre-fluxed in an aqueous solution of zinc ammonium chloride and then air dried.

Now begins the process of galvanization. The steel is completely immersed in a solution that contains a minimum of 98% pure molten zinc. The immersion is done at about 850°F (454°C), and then withdrawn slowly whereby the excess zinc is removed by draining. The steel is then cooled in ambient air or quench tank.

The last step is inspection. The two features closely scrutinized are coating thickness and coating appearance. Several physical and laboratory tests may be performed to determine thickness, appearance, uniformity and adherence.

Advantage of hot dip galvanizing is that it produces no significant changes in the mechanical properties of the structural steels or welds. Underlying steel of the galvanized product is chemically and metallurgical equivalent to the uncoated steel.

One of the processes is galvannealing wherein the surface of the just-coated steel is immediately reheated by open-air burners. Zinc alloys or metallurgical blends with steel and the surface of the strip. A galvannealed item corrodes more readily than galvanized steel. It is intended for applications where it would be painted, such as appliance panels and computer brackets.

Most ferrous materials are suitable for galvanizing including malleable iron, cast iron, cast steels, and hot and cold rolled steels.

Companies like BlueSteel Services LLC can be trusted for the quality of galvanized pipes, steel coils and electrical conduits. This site represents domestic and offshore producers in the US of finished and semi-finished steel goods.

Visit home page for gathering more information about the company’s product line. They can stand up to the challenging standards in a rapidly changing marketplace.

Author of this article is associated with BlueSteel Services LLC, which is engaged in OCTG sales, steel coils, electrical conduits, water well casing and pipes.