How to Galvanize Steel
Clean away the surface contaminants., Pickle away the rust., Put the metal in flux., Immerse the steel in molten zinc., Take the galvanized steel out of the zinc bath slowly., Cool the galvanized steel., Inspect the galvanized steel.
Step-by-Step Guide
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Step 1: Clean away the surface contaminants.
Before any other steps can be taken, the steel surface must be cleaned thoroughly.
How this is done depends on what has to be cleaned away.
Dirt, grease, oil, or paint markings require the use of a mild acid, a hot alkali, or a biological cleaning agent.
Asphalt, epoxy, vinyl, or the slag from welding need to be cleaned by sandblasting or with other abrasives. -
Step 2: Pickle away the rust.
Pickling is done with hydrochloric acid or hot sulfuric acid; it removes both rust and mill scale.
In some cases, abrasive cleaning may be enough to remove the rust, or it may be necessary to use both a pickling solution and abrasives.
In some cases, larger abrasives such as buckshot are air-blasted onto the steel. , In this case, “flux” is a solution of zinc ammonium chloride that removes any remaining rust and scale and protects the steel from rusting until it is actually galvanized. , The bath of molten zinc should be at least 98 percent zinc and maintained at a temperature range of 815 to 850 degrees F (435 to 455 degrees C).
While the steel is immersed in the zinc bath, its iron reacts with the zinc to form a series of alloy layers and an outer layer of pure zinc. , Most of the excess zinc will drain off; what doesn’t drain off can be vibrated off or spun off in a centrifuge. , Cooling the metal stops the galvanization reaction, which continues as long as the steel is the same temperature it was while immersed in the zinc bath.
Cooling can be done in one of several ways:
Immerse the steel in a passivation solution such as potassium hydroxide.Immerse the steel in water.
Let the steel cool in the open air. , Once the galvanized steel is cooled, check it to make sure the zinc coating looks good, sticks to the steel, and is thick enough.
There are a number of tests that can be performed to ensure the galvanization was successful.
Standards for hot-dip galvanizing and inspecting its results have been established by such organizations as the American Society for Testing and Materials (now called ASTM International),the International Standards Organization (ISO), the Canadian Standards Association (CSA), and the American Association of State Highway and Transportation Officials (AASHTO). : -
Step 3: Put the metal in flux.
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Step 4: Immerse the steel in molten zinc.
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Step 5: Take the galvanized steel out of the zinc bath slowly.
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Step 6: Cool the galvanized steel.
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Step 7: Inspect the galvanized steel.
Detailed Guide
Before any other steps can be taken, the steel surface must be cleaned thoroughly.
How this is done depends on what has to be cleaned away.
Dirt, grease, oil, or paint markings require the use of a mild acid, a hot alkali, or a biological cleaning agent.
Asphalt, epoxy, vinyl, or the slag from welding need to be cleaned by sandblasting or with other abrasives.
Pickling is done with hydrochloric acid or hot sulfuric acid; it removes both rust and mill scale.
In some cases, abrasive cleaning may be enough to remove the rust, or it may be necessary to use both a pickling solution and abrasives.
In some cases, larger abrasives such as buckshot are air-blasted onto the steel. , In this case, “flux” is a solution of zinc ammonium chloride that removes any remaining rust and scale and protects the steel from rusting until it is actually galvanized. , The bath of molten zinc should be at least 98 percent zinc and maintained at a temperature range of 815 to 850 degrees F (435 to 455 degrees C).
While the steel is immersed in the zinc bath, its iron reacts with the zinc to form a series of alloy layers and an outer layer of pure zinc. , Most of the excess zinc will drain off; what doesn’t drain off can be vibrated off or spun off in a centrifuge. , Cooling the metal stops the galvanization reaction, which continues as long as the steel is the same temperature it was while immersed in the zinc bath.
Cooling can be done in one of several ways:
Immerse the steel in a passivation solution such as potassium hydroxide.Immerse the steel in water.
Let the steel cool in the open air. , Once the galvanized steel is cooled, check it to make sure the zinc coating looks good, sticks to the steel, and is thick enough.
There are a number of tests that can be performed to ensure the galvanization was successful.
Standards for hot-dip galvanizing and inspecting its results have been established by such organizations as the American Society for Testing and Materials (now called ASTM International),the International Standards Organization (ISO), the Canadian Standards Association (CSA), and the American Association of State Highway and Transportation Officials (AASHTO). :
About the Author
Dennis Mendoza
Enthusiastic about teaching lifestyle techniques through clear, step-by-step guides.
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