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What is Galvanized Steel?

By S. Mithra
Updated May 17, 2024
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Galvanized steel is steel that has gone through a chemical process to keep it from corroding. The steel gets coated in layers of zinc oxide because this protective metal does not get rusty as easily. The coating also gives the steel a more durable, hard to scratch finish that many people find attractive. For countless outdoor, marine, or industrial applications, galvanized steel is an essential fabrication component.

How It's Made

One of the most common ways of making steel resist rust is by combining (alloying) it with a metal that is less likely to corrode: zinc. When steel is submerged in melted zinc, a chemical reaction permanently bonds the zinc to the steel. Therefore, the zinc isn't exactly a sealer, like paint, because it doesn't just coat the other metal; it actually permanently becomes a part of it. The most external layer is all zinc, but successive layers are a mixture of zinc and iron, with an interior of pure steel.

This process, known as hot-dipped galvanization, is one of the most common methods of making galvanized steel, but it's not the only one. Continuous sheet galvanizing runs a steel sheet or wire through molten zinc; it's also a form of hot-dipping, but leaves a thinner layer of the protective metal. Steel can also be painted or sprayed with zinc, although neither method creates the strong bond that hot-dipping does. Electrogalvanizing or electroplating uses electricity to create the bond between the two metals, which results in relatively thin layer of zinc.

The degree of galvanizing is usually described as the zinc's weight per surface area rather than its thickness, because this gives a better representation of how much metal has been applied. Steel often gets galvanized after individual parts have been formed, such as braces, nails, screws, beams, or studs. Continuous sheet galvanizing is often done before the metal is used to create products, however, and can withstand some bending and forming without flaking.

Benefits of Galvanization

Zinc protects steel in two ways. First, it is highly resistant to rust; iron, a major component of steel, reacts very easily with oxygen and moisture and will eventually disintegrate. The layer of zinc on the surface prevents those elements from reaching the steel so quickly. It also develops a patina — a layer of zinc oxides, salts, and other compounds — that offers further protection. Zinc is also extremely durable and scratch resistant, and has a satiny appearance that many find attractive.

The outer layer also protects the steel by acting as a "sacrificial layer." If, for some reason, rust does take hold on the surface of galvanized steel, the zinc will get corroded first. Even in areas where the surface is scratched or damaged, the surrounding zinc will still corrode before the steel does. The lifespan of galvanized steel varies, but industrial steel with a 3.9 mil (0.0039 inches or 0.09906 mm) thick coating can last more than 70 years without maintenance under average conditions.

Uses

Galvanized steel can be found almost everywhere. Many individuals live in steel frame houses, and buildings are often made with galvanized steel roofs. There are multiple steel parts in cars that help protect them from the weather, and it's used in many marine applications due to its ability to withstand the salt and the elements. Besides being inexpensive, durable and effective, this metal is also popular because it can be recycled and reused multiple times.

Disadvantages

There are relatively few disadvantages to galvanization, but it's not a good method for protecting all steel items. Some objects cannot be hot-dipped, often because they are too large or too small, and other forms of galvanizing often are not as protective and long-lasting. Eventually, the zinc will be corroded, although how long this takes depends on the thickness of the coating and the environment. Galvanized steel has a much shorter lifespan when it's regularly exposed to rain or seawater.

Galvanized steel that is cooled too slowly or stacked together before they have cooled completely can also have the outer zinc layer peel away. In some cases, small gaps can form between the zinc and the underlying alloy, which can also cause peeling. When a very thick coat of zinc is applied, it can also become brittle and flake off.

Alternatives to Galvanization

Some metal items cannot be galvanized effectively; the coating of zinc would be too thick on a small screw, for example. In many cases, stainless steel, made with chromium, is used instead. Unlike galvanized metals, stainless steel is not coated in the metal; chromium is part of the composition of the steel alloy.

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Discussion Comments

By anon945497 — On Apr 13, 2014

Can you use galvanized wire as a heat conducting source for a vaporizer?

By anon346373 — On Aug 28, 2013

What is the function? Why we are using m.s instead of GI?

By anon333646 — On May 07, 2013

Galvanized material may be toxic for cooking.

By anon288203 — On Aug 28, 2012

Many questions regarding the "strength" of galvanized steel. The strength of the steel is affected by the steel chemistry, cold working (if any) and annealing. Galvanizing is only the application of a protective zinc coating.

Since the coating is less than 99 percent zinc and zinc has a boiling point of less than 1650F/900C, there is little chance of smoke unless you weld or hit it with a live wire. The coating will melt at a much lower temp: ~770F.

By anon281468 — On Jul 24, 2012

In a galvanised steel of zinc nickel alloy for an hot dip galvanizing, in the case of getting a scratch between the zinc and nickel, which one will corrode first for the sacrificial layer to protect the iron underneath?

By anon274327 — On Jun 11, 2012

I want to know if it is possible to change the iron galvanised steel sheet into an only iron steel sheet by removing the zinc coating.

By anon177532 — On May 18, 2011

If you are the paranoid type, don't plant food in galvanized steel in case for some unforeseen reason the (likely used... see online) lead in it would get scratched or leached off into the soil. No idea if that is likely at all, but maybe.

By anon176726 — On May 16, 2011

Is it safe to plant herbs that you would eat in galvanized steel (specific material content is steel, galvanized steel and polyester powder coating)?

By anon170671 — On Apr 27, 2011

What kind of sealer can you use?

By anon168941 — On Apr 19, 2011

Can someone please help me understand the difference between schedule 90 and schedule 40 galvanized steel blanks? Thank you. --Cheryl

By anon151810 — On Feb 11, 2011

I want to make a wood fire oven that will go up to 1000 F. can you suggest what steel would work best for this application. I want to take a 4'x 8' sheet and roll it into a have moon shape.

By anon150873 — On Feb 09, 2011

can I use galvanized steel for steam lines at 200C?

By anon142895 — On Jan 14, 2011

can you burn in a galvanized garbage can?

By anon135839 — On Dec 20, 2010

is there a difference between galvanized and metallic coated steel?

By anon133924 — On Dec 12, 2010

@anon129960 (#87) - The durability can range between 14 and 20.6. Sometimes it displays anomalies of up to 67, but not very often. Study the peaks and troughs of your sample analysis to predict when this will happen.

By anon129960 — On Nov 26, 2010

Could you tell me the durability of galvanized welded wire mesh wire.

By anon120685 — On Oct 21, 2010

I would like to know if electric elements keep zinc molten?

By anon119168 — On Oct 16, 2010

Is there a chemical equation for galvanized steel?

By anon119128 — On Oct 16, 2010

what gauge would hot rolled sheet metal be if it was 1/8" thick?

By anon116177 — On Oct 05, 2010

will the strength of the steel section improve after galvanization? or are there any factors to be considered while calculating the design strength of the steel section?

By anon114518 — On Sep 28, 2010

by what process we can remove the zinc coating from galvanised iron?

By anon113283 — On Sep 23, 2010

I would like to know if any bat or bird droppings would corrode galvanized steel.

By anon112819 — On Sep 22, 2010

why does iron not corrode even after the zinc layer is scratched off?

By anon110823 — On Sep 13, 2010

is it flexible?

By anon102254 — On Aug 07, 2010

Robert Galvin? ROFL.

The Galvanic process was discovered by Luigi Galvani in the 1700s. He was the inventor of the chemical battery (Galvanic cell) as we know it now. Galvanization is the name given to electrochemical processes in his honor. Galvanizing steel (hot-dipping as correctly depicted in the article) is not an electrochemical process but the result is the same, so someone decided to keep the name.

By Engelsrud — On Jul 07, 2010

Whats the best way to recondition or clean dirty and grimy galvanized street light poles?

By anon93188 — On Jul 02, 2010

Galvanizing steel, no doubt is protecting the underlying steel but what if it has not been applied properly or there are small pores in the coating? Yes, there will be a rapid corrosion started due to high anode to cathode area. Aforementioned fact greatly implies that the coating is free from defects; otherwise protection does not work as expected.

By anon92383 — On Jun 28, 2010

Could you please explain about spangle variation? Due to spangling on a galvanised metal sheet not being smooth and in the same sheet it makes different sized of spangles. So what is the factor which can make this problem? How can it be improved?

By anon90953 — On Jun 18, 2010

please give information on how to establish a galvanized steel plant? Actually one of my friends has got a contract for galvanized steel. so I want total information about plant, temperatures, voltages, current and apparatus required.

By cathy123pipe — On Jun 01, 2010

The galvanized pipes contain hot-dipped galvanizing and cold galvanizing. The quality of the zinc layer is different.

By anon84285 — On May 14, 2010

I must agree with the one comment about lots of questions but no answers. I too, am curious about galvanized metal and heat. Is it better to cook or burn off the galvanization? I have a galvanized container that I want to turn into a camp stove.

By anon79676 — On Apr 23, 2010

Can you safely put a galvanised metal sheet (the spotty looking metal sheet) alongside a zinc sheet without the two reacting?

By anon79258 — On Apr 21, 2010

No it is not magnetic!

By anon78780 — On Apr 20, 2010

Is galvanized steel really safe? We have it everywhere. -magde09

By anon77832 — On Apr 15, 2010

Can 50 year old galvanized steel water pipes result in lead readings in the water? I had the city water tested and the results indicated levels of lead above the MCL (0.015). Is this likely due to other city contaminants from old city water piping?

By anon76025 — On Apr 08, 2010

Galvanized carbon steel is used for drinking water pipes, but isn't is harmful for the human body?

because if zinc layer acts as sacrificing layer, then zinc may get in water.

By anon68589 — On Mar 03, 2010

Can galvanized steel bolts be use in bolting together two carbon steel structures?

By anon67866 — On Feb 27, 2010

"Robert Galvin is the man who invented Galvanized metal. He discovered it when he dropped a spoon in a tub of liquid zinc (originally for the mayor for reasons unknown) and found that it didn't rust like the rest. He then made a note of them and nicknamed the spoon the "Galvanized spoon"."

whoever said this is full of it. The Galvanic process has been around for hundreds of years, and has nothing to do with someone's last name.

By anon63372 — On Feb 01, 2010

Clean off the galvanized iron. If you have a large piece of metal, pressure-wash it to remove as many rust flakes as possible. If the item is smaller, rinse it with a garden hose. Once the item is rinsed clean, wipe it down with a damp rag that has three drops of liquid detergent on it. This will remove dust, dirt and grime so that the rusted areas are easier to spot.

Mix up your oxalic acid. Oxalic acid, also called wood bleach, comes in a powdered form and generally is mixed with water to form a liquid. To treat rust on galvanized iron, however, measure several cups of the powder into the plastic bucket, then add water a cup at a time until a thick paste has formed that can be spread, but that will not run. Wear your gloves and goggles during this step and from this time forward.

Spread the oxalic acid paste on the rust spots. Cover them completely, and allow the paste to sit on the spots for five to 10 minutes. You may see the rust "lifting" off the metal and staining the paste. Do not leave the paste on the metal for more than 10 minutes.

Rinse off the wood bleach paste. Use the pressure washer or the garden hose to thoroughly rinse off the area. Once it is clear, tackle any remnants of rust or rust stains with the wire brush until they are completely gone.

Clean the galvanized metal thoroughly. Use the pressure washer or hose and the cleaning rags with liquid detergent to wipe down the entire area and make sure that all oxalic acid residue and rust residue is completely gone. Dry the metal rather than allow it to air dry to prevent flash rust formation.

By anon61664 — On Jan 21, 2010

Fifteen years ago, my builder installed a galvanized steel sheeting drip pan beneath my washer and dryer in my laundry room. It has developed large blotchy rust stains in some places. I am about to have a new washer and dryer installed tomorrow and would like to be able to clean up the drip pan first.

Does anyone know what I should use to remove the rust? Thanks! --anonymous

By anon60284 — On Jan 13, 2010

how much galvanized steel is used in construction purposes?

By anon57664 — On Dec 25, 2009

what is the difference between the hot dip galvanize and galvanized sheet?

By anon52797 — On Nov 17, 2009

We are pipe galvanizers. After galvanizing we directly dip the pipe in a solution of sodium dicromate+ 0.1 percent sulfuric acid. After the pipe is taken out from the passivation solution, there are yellow marks on the pipe. How do we remove the marks and are we doing passivation properly.

By anon52332 — On Nov 13, 2009

I agree with you about the degree of galvanising. would you please let me know what is the difference among class A, Class B and Class C? I mean the weight range for the above three.

By anon52235 — On Nov 12, 2009

Robert Galvin is the man who invented Galvanized metal. He discovered it when he dropped a spoon in a tub of liquid zinc (originally for the mayor for reasons unknown) and found that it didn't rust like the rest. He then made a note of them and nicknamed the spoon the "Galvanized spoon".

By anon50445 — On Oct 28, 2009

What is the thermal conductivity of typical galvanized steel? A quick answer would be much appreciated, thank you.

By anon47516 — On Oct 05, 2009

Do I need to make adjustments to my weld schedule if I am resistance spot welding Electrogalvanized vs Hot Dipped galvanized sheet metal?

By anon46359 — On Sep 24, 2009

who invented this method?

By anon44338 — On Sep 07, 2009

Most galvanized steel is coated with a passivation chemical to prevent "white rust". A common passivation chemical used is Hexavalent Chromium; a very harmful carcinogen when ingested, absorbed by the skin, or inhaled. Welding and other heating of galvanized steel can allow the passivation chemical to be liberated and thereby create a health concern. -- Jerry Lavoie

By anon43229 — On Aug 26, 2009

Can galvanized steel be forged safely?

By anon42685 — On Aug 23, 2009

galvinised steel can be welded as i welded a butt arch joint at school the other day.

By anon39815 — On Aug 04, 2009

If galvanized steel were used for a laptop lock, could a thief easily cut through it compared to a bike U-lock?

By anon37553 — On Jul 20, 2009

can galvanised steel be painted?

By anon36853 — On Jul 15, 2009

galvanized bolts and nuts can be used in electrical termination ? where we have to maintaine low joint resistance ie good bonding

By anon35910 — On Jul 08, 2009

Nathan it depends on your steel thickness to the amount of zinc coating needed to that particular part. minimum thickness and galvanized coatings are measured in mils

By anon35908 — On Jul 08, 2009

You cannot weld galvanized steel. you must first strip it down to the bare metal and then regalvanize it.

Depending on the type of acids and degreaser your galvanizer is using will vary on the types of fumes released.

Steel is not magnetized during the galvanizing process.

Using galvanize grill screens are safe as long as you do not heat the screen over 730 degrees.

Galvaning is measured in mils not G-000.And it depends on your steel thickness and chemistry of the steel to the amount of zinc that part would pick up.

Galvaneal Coating (A) - Coatings on hot-dipped galvanized steels processed to convert the coating completely to zinc-iron alloys; dull gray in appearance, have no spangle, and after proper preparation, are well suited for painting.so this goes over the galvanized coating.

By anon35247 — On Jul 03, 2009

Does no one answer these questions? and if so, where?

If heated, will galvanized steel release harmful toxins?

By anon33543 — On Jun 08, 2009

Would galvanised steel, electroplated steel or steel painted with anti-rust paint be the best type of steel to use for ship building?

By butel1208 — On May 23, 2009

I'm disappointed. I see lots of questions but few answers. I was particularly interested in knowing if galvanization on metal was a health hazard such as the question of whether a galvanized wire mesh could be used as a grill on the barbecue?

By REMuns — On Mar 22, 2009

just want to read responses to above postings

By anon22619 — On Dec 07, 2008

As per code requirements, I am installing a heat shield on combustible walls and ceiling around my woodstove. They recommend sheet metal. I have several 4' X 8' sheets of good heavy galvanized sheet metal I would like to use. I expect temps. somewhere around 300 / 350 degrees max. or lower. Is there any fuming I should be concerned with?

By charlie44 — On Dec 04, 2008

I have a galvanized chimney that goes from my gas furnace to my chimney and out in the attic.

Sometimes rain comes down the chimney and shows a white powder on the galvanized in the attic area. I think this is corrosion. I was told it is not and would never corrode through. Is this true, or should I be concerned. Thank you,

Charlie

By anon18416 — On Sep 22, 2008

what's galvanized steel's SRI? (Reflectivity and emissivity)?

By anon17564 — On Sep 02, 2008

Galvanized pipes are available in Above ground pipes up to what size?

By nkiruevan — On Aug 30, 2008

can galvanized steel be welded?

By jdarden — On Aug 21, 2008

I used a galvanized garbage can to season my Dutch Oven. I got the internal temp. up to 400 degrees F. Someone mentioned that I might have gotten fumes from the zinc in the oven. From my understanding, zinc will not turn to gas until it gets to over 900 degrees C. My question is: Is seasoning my Dutch oven this way safe? Also, is it safe to cook a turkey in a galvanized garbage can?

By pixiedust — On Aug 16, 2008

anon16792 - Galvanize is just a coating. So the strength goes to the steel, not the _galvanized_ steel. There are different strengths: tensile, yield, compression, shear. Strength depends on whether the steel is hardened, annealed... When you talk about strength you have to specify all those elements, plus the material itself, if it is carbon steel, stainless steel, alloy steel....

anon16449 - yes, galvanized steel attracts magnets.

By anon16792 — On Aug 15, 2008

what is the shaer stress of galvanized steel

By anon16449 — On Aug 06, 2008

Does galvanized steel attract magnets?

By anon13918 — On Jun 06, 2008

is galvanized steel worth more than original steel?

By anon13648 — On Jun 02, 2008

galvanization can affect the stainless steel when installed together?

By jgonzales — On May 19, 2008

What is the difference between galvanized steel, perma-gold, electro-galvanized, pregalvanized and hot dip galvanized? If the difference is the thickness of the zinc galvanized finishes, what is the service life for each of these finishes?

By alig — On Apr 26, 2008

what are performance factors, safety, purpose and durability of galvanized steel

By tom2514 — On Apr 25, 2008

What is the chemical makeup of galvanized steel?

By tom2514 — On Apr 23, 2008

If you dropped a burning charcoal red ember on Galvanized Steel, is there anything harmful in the make up of Galvanized Steel that could release toxic fumes? Would it be able to withstand the heat from a burning charcoal red ember?

By anon11155 — On Apr 09, 2008

What is the difference between Galvanized steel and Galvaneal Steel?

By anon5803 — On Dec 06, 2007

I have a gas log fireplace non vented. I want to place a thin galvanized plate above fire about 15". Will it get too hot?

By alipishi — On Nov 29, 2007

Can galvanized steel be welded?

By Nathans — On Nov 21, 2007

I saw on another website that the thickness is measured ranging from G-30 to G-235. How thick is that, and when is the thicker coating used?

By anon4954 — On Nov 07, 2007

Can galvanized steel (Roofing) be soldered? thank you, tom rosdick

By gfain — On Oct 19, 2007

Can a galvanized trash can be used to cook food by using the trash can as a type of outdoor oven. I've read an article about cooking turkeys in a trash can. The article said to burn the trash can before using it to cook.

By anon3682 — On Sep 11, 2007

How thick is the zinc layer of galvanized roof flashing?

By stanmasch — On Sep 09, 2007

Is it safe to use a galvanized wire mesh as a grill in my barbecue grill?

By anon2978 — On Aug 03, 2007

is it true that galvanized springs used in garage doors, are weaker than regular coated springs?

By ronchis — On Jul 19, 2007

does galvanized steel give off bad fumes if it gets too hot?

By anon2532 — On Jul 15, 2007

is it safe to burn in a galvanized bucket, or does it make toxic fumes? does the zinc coating produce fumes, and if so are they safe.

By anon2481 — On Jul 13, 2007

is galvanized steel magnetic?

By cordellv — On Jun 27, 2007

Can you use galvanized steel from an air conditioning duct to make a meat smoker? Will fumes from the zinc come off in the smoke and harm you. Is there anything else in the galvanization process besides zinc that could give off fumes?

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