KnowledgeBase » Zinc Coatings
Batch Hot-Dip Galvanizing Production Process
The batch hot-dip galvanizing process, also known as general galvanizing, produces a zinc coating on iron and steel products by immersion of the material in a bath of liquid zinc. Before the coating is applied, the steel is cleaned to remove all oils, greases, soils, mill scale, and rust. The cleaning cycle usually consists of a degreasing step, followed by ...
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Is it possible to have steel with chemistry too good for galvanizing?
It is possible to have steel chemistry with levels of silicon and phosphorus that are too low to meet the minimum thickness levels specified in ASTM A123 and ASTM A153. Very low silicon levels are seen more often on pipe though, not plate because aluminum is sometimes used as a deoxider rather than silicon.
For steel with very low levels of silicon and/or phos...
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Why is lead added to the galvanizing bath?
Lead is not purposely added to galvanizing baths, rather it is an impurity in zinc. Different types of zinc have different levels of lead. The specified lead maximums for the various types of zinc can be found in ASTM B6.
Lead does have the beneficial effect of decreasing the surface tension of zinc, which allows it to flow off the steel easier as it is being removed from the kettle. This creates thinner galvanized coatings that have l...
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Zinc Coatings and Applications Chart
The zinc coatings and applications chart displays zinc coatings and their application methods. It provides information on the process, specification details, coating thickness, and application. See the Zinc Coatings Publication for more detailed information.
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Coating Characteristics of Continuous Sheet Galvanizing
After galvanizing, the continuous zinc coating is physically wiped using air knives to produce a uniform coating across the width of the strip. The uniform coating consists almost entirely of unalloyed zinc and has sufficient ductility to withstand deep drawing or bending without damage. A variety of coating weights and types are available, ranging up to just over 3 mils (76 µm) per side. One of the most common zinc coatings is Class G90, whic...
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Zinc Painting Production Process
Zinc-rich paints typically contain 92-95% metallic zinc in the film of the paint after it dries. The paints are applied by brushing or spraying onto steel cleaned by sand-blasting. While white metal blasting (NACE No. 1) is preferred, near white (SSPC-SP 10) or commercial blast cleaning (SSPC-SP 6) are acceptable.
When the zinc dust is supplied as a separate c...
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Zinc Plating Production Process
Zinc plating is identical to electrogalvanizing in principle because both are electrodeposition processes. Zinc plating is used for coatings deposited on small parts such as fasteners, crank handles, springs and other hardware items.
The zinc is supplied as an expendable electrode in a cyanide, alkaline non-cyanide, or acid chloride salt solution. Cyanide baths a...
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Coating Characteristics of Zinc-Rich Paint
Organic or inorganic zinc-rich paints are applied to a dry film thickness of 2.5 to 3.5 mils (64 to 90 µm). Organic zinc paints consist of epoxies, chlorinated hydrocarbons, and other polymers. Inorganic zinc paints are based largely on organic alkyl silicates. The zinc dust must be at a concentration high enough to provide for electrical conductivity in the dry film ...
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Coating Characteristics of Electrogalvanizing
This electro-deposited zinc coating consists of pure zinc tightly adherent to the steel. The coating is highly ductile and the coating remains intact even after severe deformation. The coating is produced on strip and sheet materials to coating weights up to 0.2 oz/ft2 (60 g/m2), or thickness up to 0.14 mils (3.6 µm) per side. On wire, coating weights may range up to 3...
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Zinc Spray
Zinc spray, which is also referred to as metallizing, is done by melting zinc powder or zinc wire in a flame or electric arc and projecting the molten zinc droplets by air or gas onto the surface to be coated. The zinc used is nominally 99.5% pure or better and the corrosion resistance of the coating produced by this technique is approximately equal to the hot-dip galvani...
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