What Is Galvanization?
Galvanization is the process of applying a protective coating to steel or iron. The coating is made from zinc and is used to halt the formation of rust. Galvanization is important because it provides long-lasting protection for steel and iron products.
How Does Galvanization Protect the Base Metal Underneath?
1. The zinc coating prevents corrosive substances like acid (acid rain for example) from reaching the metal underneath.
2. Galvanization protects from rusting. When the coating is scratched, zinc will still “sacrifice its anode” easier than the base metal does – which protects it from rusting.
Learn more about how and why metals rust in our blog: Which Metals Rust?
3. The zinc protects the metal by corroding faster than the base metal. Sometimes a special ingredient called a “chromate” is added to the galvanized metal, this makes it corrode even faster. It may sound like that is not what you want to happen, but remember the zinc corroding before the metal is what protects the metal underneath from rusting.
You can tell when metal is galvanized because the zinc makes a distinctive pattern on the metal called “spangle.”
What Is The Galvanization Process?
There are a few methods of galvanizing metal. The most common method is the hot-dip galvanization process. This method of galvanization creates a nice, thick layer of zinc on top of the base metal – which makes it extra resistant to corrosion. For the most part, the hot-dipping process doesn’t sacrifice the structural integrity of the metal, but some very high-strength steels can suffer from hydrogen embrittlement.
The steel used in car bodies is also galvanized, but because layers of decorative paint need to be applied afterward – they use a different galvanization process. This is because the zinc layer from the hot-dip method is too thick, and causes issues with the paint adhesion.
Instead, automobiles use the electrogalvanization process. A solution of salt water (saline) and zinc is put into a tank, and the steel or base metal is dipped inside. An electrical current is run through the vat, and the zinc bonds to the base metal!
A special form of galvanizing, called Sherardizing, is used to create a zinc coating on iron or copper products. It was created by metallurgist Sherard Osborn Cooper-Coles and patented around 1900.
The metallic parts that are to be galvanized are put inside of a closed, rotating drum along with zinc powder, and sometimes a filler like sand. The drum is then superheated to 500C. At temperatures above 300C, zinc turns into a vapor – and this vapor penetrates the metal turning inside of the drum.
This process is also called “dry galvanizing” because there are no liquids used.
This is probably how many small parts around your home, like screws or nuts and bolts, have been galvanized. This process doesn’t use any hydrogen, so hydrogen embrittlement can’t happen during this method of galvanizing.
5 Benefits of Galvanizing
If you’re looking to buy steel for your next project, consider opting for galvanized steel. Galvanized steel touts numerous measurable benefits, including the following:
1. Economical: Choosing galvanized steel initially may seem more expensive, but it’s a great investment in the long run. Moreover, galvanizing is actually cheaper than many other protective steel coatings.
2. Low-maintenance: Steel that lacks a protective coating requires more maintenance to upkeep the appearance and structural safety of the product.
3. Long Lasting: Galvanized steel coatings can have a life expectancy of up to 50 years and can withstand urban and coastal exposure.
4. Unparalleled Protection: Every inch of galvanized steel is protected—this includes sharp edges and those hard-to-reach crevices.
5. Fast: The process of galvanizing is fast and easy. In fact, a full protective coat can be applied in just a few minutes.
How Can You Use Galvanized Metal?
Galvanized metals are used everywhere!
The bodies of cars and many bicycles are made from galvanized metals. Some drinking water pipes are still made from galvanized steel. Cool rolled sheet metal is also frequently galvanized.
Nuts, bolts, tools, and wires of all kinds are now galvanized because it is a cheap process, and definitely helps boost the metal’s lifespan!
Galvanized steel, in particular, is often what is used in modern “steel frame” buildings. Galvanized steel is also used to create structures like balconies, verandahs, staircases, ladders, walkways, and more.
Galvanized metal is a great choice if your project will live outside after it’s done. Fences, roofs, rain gutters, outdoor walkways, these are all great choices for galvanized metal!