Galvanizing is a Common, and Very Effective, Protective Metal Coating

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Galvanizing is a process used on iron and steel, protecting them from corrosion. It involves coating the surface with zinc (galvanic action), which prevents oxidation.

There are several ways that galvanizing acts as a protective metal coating, but it’s not commonly thought of as an external coating. Galvanizing doesn’t have to be limited to certain types of metals and only certain surfaces.

Read on to learn more about how galvanizing protects iron and steel and other common household items that are also protected by galvanizing. These details explain why galvanized metal is so effective at preventing corrosion in many applications.

What is Galvanizing?

Galvanizing applies a protective coating to steel and iron before or after the metal has formed into its final shape. Galvanizing iron or steel involves dipping the iron or steel into a bath of molten zinc at high temperatures.

Here’s an explainer from Youtube:

To produce a quality coating, the iron or steel must be clean and free of rust or other contaminants. The galvanizing process creates a chemical reaction that bonds the zinc to the underlying iron, and the resulting zinc coating has high corrosion resistance.

I explained the roots of galvanizing in an article on our sister site, Schuette Metals’ Fab Times. It all began with the application of current to a deceased frog:

We derive the name Galvanization from Luigi Galvani (1737-1798), an Italian anatomist and physician. He investigated the phenomenon of bioelectrogenesis. Around 1780, Galvani experimented by applying current to muscles or nerves of frogs and other animals. He observed the current caused muscle contraction.

Those experiments used a Leyden jar or a rotating static electricity generator. However, an incident with a frog became famous.

In the strange case of Galvani’s frog, this twitching happened even when its legs were not in a direct circuit with the machine. Galvani had placed the lower section of a dissected frog on a table near a plate-type electrical machine.

Then two things occurred simultaneously, causing Galvani to stop and wonder. An assistant was drawing a spark from the brass conductor of the electrical machine when a knife held in his hand touched the crural or sciatic nerve passing through the lower part of the spine into the frog’s legs. There was an immediate twitch of the muscles and a kick of the legs as if a severe cramp had set in. Galvani wrote, “While one of those who were assisting me touched lightly, and by chance, the point of his scalpel to the internal crural nerves of the frog, suddenly all the muscles of its limbs were seen to be so contracted that they seemed to have fallen into tonic convulsions.

Trivia: Galvani’s work inspired Mary Shelley to write Frankenstein.

How does Galvanizing Protect Metal from Corrosion?

Its conductivity is a critical aspect of galvanizing, enabling it to protect the metal from corrosion. In the galvanizing process, a thin layer of zinc coats the surface of the steel, forming a strong chemical bond with the steel, and the two metals become one through electrochemical corrosion.

The resulting conductive surface of the galvanized metal prevents corrosion of the steel below. So, rather than the steel corroding and rusting, the zinc corrodes. The galvanized metal, therefore, provides a protective coating, allowing the steel to remain intact for many years.

It’s important to note that galvanizing only protects the surface of the metal it applies to. Therefore, it is important to regularly coat the surfaces of objects made from steel or iron to increase their longevity.

Benefits of Galvanized Metal

  • Anti-corrosive properties: As discussed above, galvanizing protects metal from corrosion, meaning it’s ideal for applications such as water towers, water pipes, and even building roofs.
  • Energy efficiency: Many energy-producing facilities, such as hydroelectric dams, require metal equipment to be protected from corrosion, and these facilities are expensive to run and can deliver reliable energy. Galvanized metal is ideal for protecting these features, as it prevents rusting, reduces the need for maintenance, and increases the life span of these structures.
  • Safety: Galvanized metal is also ideal for areas at risk of corrosion. For example, they use galvanizing in marine environments, such as piers or other areas where water and salt are present.
  • Cost: Compared with other materials used for protective coatings, such as paint, galvanized metal is relatively inexpensive and low maintenance.

Which Household Items are Galvanized?

  • Roofs: Often, roofing uses galvanized metal to protect it from the elements and reduce the need for maintenance.
  • Water towers: Galvanized metal is also used to protect water towers, which are essential equipment in many communities.
  • Wires: Many electrical wires, including those running between utility lines and buildings, use galvanized iron or steel because of their corrosion resistance.
  • Farm equipment: Other household items using galvanized metal include tractors, harvesters, balers, and more.

Common Galvanized Objects

  • Cars: Cars use galvanized steel components to protect them from corrosion, protecting doors, trunk lids, hoods, roofs, and other components.
  • Bridges: You might not think about it, but bridges fight corrosion, too. They frequently apply galvanized metal to bridge decks, girders, and other parts.
  • Bikes: Bicycles often feature metal parts made from galvanized steel or iron, protecting the bike from rust due to wet weather, humidity, or salty air.
  • Kitchen appliances: Other things that galvanized metal may protect include kitchen appliances, like microwaves, refrigerators, stove tops, and more.

Is Galvanizing the Same as Coated Steel?

You may also hear the term “coated steel” in metal protection. However, galvanizing and coating are two very different processes. The major difference between galvanizing and coating is that galvanizing is a process in which two metals bond together. In contrast, the process of coating is when one metal adheres to another. The applied coating acts as a protective surface, whereas galvanizing is the actual bonding of two metals. Galvanized metal protects against corrosion because of its chemical composition. The coating applied to metal, on the other hand, protects the surface of the metal, but the metal itself is still susceptible to corrosion.

Summing up

Galvanizing is used to protect steel and iron from corrosion. It involves dipping the iron or steel into a bath of molten zinc at high temperatures, and the resulting zinc coating has high corrosion resistance.

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