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Weld Slag Clean Up Requirements for Galvanizing

When welded structures are hot-dip galvanized, the weld area cleanliness significantly affects the quality and appearance of the galvanized coating around the weld.  If a coated electrode (i.e. a flux-coated welding wire/rod/stick) is used during welding, all welding flux and slag must be cleaned prior to galvanizing or the ...
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Reasons for Duplex Coating

There are seven good reasons to paint or powder coat hot-dip galvanized steel: Extended Durability – in what is called the synergistic effect between galvanized steel and paint, the zinc of the galvanized coating is a barrier protection to the substrate steel, cathodically protects it, and provides underfilm corro...
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How to Clean Wet Storage Stain

Treatment of wet storage stain begins with drying the galvanized surface. As long as water remains on the zinc surface, and airflow is limited, the corrosion mechanism responsible for wet storage stain will continue, and can damage the zinc coating and underlying steel. After the galvanized surfaces are dried, the treatment processes differ dependi...
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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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Bracing (temporary and permanent) of steel fabrications for galvanizing

Most fabrications lend themselves well to the galvanizing process, including asymmetrical designs or structures containing sections of unequal thickness. It is important to understand that, because during galvanizing steel is exposed to temperature variations, fabrications of asymmetrical design or with sections of unequal thickness can exhibit different thermal expansion and contraction stresses, leading to changes in shape and/or alignment (...
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Repairing damaged or uncoated areas of hot-dip galvanized coatings

Although galvanized coatings are highly abrasion resistant, coating damage may occur once the galvanized steel leaves the galvanizer’s facility due to extremely rough handling, installation techniques, or in-service conditions. Occasionally, small areas of the galvanized article may be bare due to unseen contaiminants the cleaning process is unable to remove. There are methods available to ensure post-galvanizing coating integrity and ASTM A78...
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Can non-members get technical support from the AGA?

One of the benefits of being a member of the American Galvanizers Association (AGA) for galvanizers is free unlimited technical support. The AGA technical staff will answer questions pertaining to the galvanizing process and job-specific problems such as appearance or other issues. Some of the dues AGA members pay goes to the cost of researching technical problems. Because of this, ...
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Why is steel chemistry important in the hot-dip galvanizing process?

Galvanized coatings are formed by a chemical process during which steel and zinc metallurgically bond, forming a series of corrosion-inhibiting, highly abrasion-resistant zinc/iron alloy layers. Galvanized coatings are specified for their corrosion resistance. While a gray or matte appearance may occur, the corrosion protection afforded is no different than that provided by shinier galvanized coatings. The corrosion resistance of matte...
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Atmospheric corrosion of hot-dip galvanized steel

The corrosion rate of zinc is directly influenced by atmospheric conditions. Certain factors that specifically affect the corrosion of zinc include: temperature, humidity, rainfall, sulfur dioxide (pollution) concentration in the air, and air salinity. None of these factors can be singled out as the main contributor to zinc corrosion, but they all play a role in deter...
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Preparing the hot-dip galvanized steel surface for painting or powder coating

Similar to painting over black steel, surface preparation is critical when painting or powder coating over the zinc coating of hot-dip galvanized steel. However, before any surface preparation takes place, the galvanizer should be notified the steel will be painted. With this understanding, the galvanizer will forego any post-treatments that could af...
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