Why Zinc is Used in Galvanization

Anyone who has lived near the coast and has owned a pre-1980s motor vehicle will be able to explain the importance of galvanizing base metal products. When metals are exposed to environmental factors like oxygen and salt, they corrode. Regardless of the make, model, cost, or level of luxury supplied by the manufacturer, without the galvanization barrier being applied to their metals, precious few of these vehicles survived the inevitable progression of oxidation.

Galvanization is the process of protecting steel, iron, or other metals from rusting by covering them in a layer of zinc or other protective shields. In layman’s terms, it is the bodyguard for a very important product (VIP). The galvanizing of the base metal with a more reactive metal protects it against the elements and other harmful agents that may cause it damage.

The VIP is only as safe as the level of skill and experience of the bodyguard protecting it. Using this analogy, the metal that is protected by the process of galvanization is only as safe as the level of knowledge, experience, and expertise of the company applying the galvanizing.


Why Do Metals Need Galvanizing?

Galvanization - Armco

Another comparison with the pre-1980s motor vehicle. All metals rust. This is a natural reaction that occurs at a molecular level. When an atom of metal, which is positively charged, attracts chemicals or particles of a negative charge such as oxygen in water, they form ferrous oxide (oxidation). The result of oxidation is rust. Add salt to the water, and it acts as an electrolyte wherein it will allow the metal to lose electrons more easily. Metals exposed to these elements that have not undergone the galvanization process will therefore rust more rapidly.


This only proves that metals rust more rapidly closer to the coast. However, all water (H²O) contains oxygen. So, all metals exposed to water, even in its vapour form, will rust, close to the coast or not. But, when two metals are exposed to H²O with a moving charge flowing through them, one will erode faster, and be more reactive to the oxygen than the other.


Galvanization Using Zinc  

Upon further research, it was discovered that zinc, which is commonly used in galvanizing today, was more reactive than aluminium. Aluminium reacted faster than cadmium, and cadmium faster than cast iron. In turn, cast iron reacted faster than carbon steel, stainless steel, lead, and solder, in that order. Solder, then proved more reactive than tin and tin more than copper.

This finding proved that more reactive metals protected less reactive metals. Therefore, other irons or steels that are less reactive, when covered with a film of zinc, which is more reactive in the galvanization process, the zinc would protect the others against oxidation.


Hot-Dip Galvanizing

In May 1837, the French chemist and civil engineer, Stanislas Sorel filed a patent for a method of galvanizing iron or steel. The process involved bathing the cleaned latter two metals in molten zinc. This formed a protective film, preventing the other two from corroding. Later, more modern techniques were introduced, such as advanced electro-galvanization and powder coating.

The barrier formed by the zinc causes its chemical reaction with the oxygen, thereby protecting the other two covered materials. Even if the protective film was scratched or partly damaged, the corroding process was delayed. This patent led to the industrial application of hot-dip galvanization and proved to be able to withstand the elements for more than 50 years.


Observations of how Galvanization Prevents Rust

  • Galvanizing forms a barrier of zinc between an underlying metal (steel or iron) from corrosive particles.
  • Once galvanization takes place, the zinc barrier reacts with the atmosphere, forming a compact cohesion of particles that is insoluble in water.
  • Zinc is therefore the sacrificial anode in the galvanizing process, protecting the base metal even when the coating is scratched.


Why is Zinc Preferred for Galvanization?

If metals such as stainless steel and copper don’t rust, why are they not used for galvanizing?

As previously proven, more reactive metals, like zinc, offer protection for those that are less reactive. Thus, zinc offers better protection for steel and iron. Copper, on the other hand, is less reactive than the others. If copper is used in galvanizing more reactive metals such as steel or iron, and the coating is damaged in any way, the copper would stay intact and the protected steel or iron would rust.

This does not mean that copper is without its uses as a galvanizing agent. Architects, engineers, and fabricators may sometimes look for an aesthetically pleasing, weathered appearance. Steel can be dipped in a copper coat to weather the metal, giving it the desired effect.


Hot-Dip Galvanization in Construction

Galvanizing is an important process in construction, and metals have many applications in the industry. But should they be used without the hot-dip galvanization process using zinc, being exposed to the elements will induce oxidation. Other chemicals can also corrode metals. This may affect the tensile strength of the material which, in turn, poses a risk to the overall integrity of the building.

Hot-Dip galvanization using zinc is sustainable, environmentally friendly, and is one of the strongest protective options for steel or iron products. It is very low maintenance and cost-effective about most other methods of protection because of its strength and durability. Zinc forms a permanent bond to the metal it is protecting, reducing exposure to the elements and extending its lifespan.


The Right Bodyguard for the Right Job

Randfontein Armco Galvanization PlantIf you are going to be protecting iron or steel from the elements that can destroy them prematurely, then you need the right bodyguard to do the job. Armco Superlite, which has its roots firmly grounded in the hot-dip galvanizing industry and is listed by the BSI ISO 9001:2015, is a brand leader in protecting iron and steel. Additionally, Armco holds the SATAS mark of hot-dipped galvanizing, and all our galvanization products are produced in accordance with the SANS 121/ISO 1461 specifications.


Armco Superlite has two major galvanization plants based in Gauteng and has the capacity to cater to all sectors, from light to heavy industry, government projects, and the mining industry. For professional, cost-effective solutions, consult with Armco Superlite. Our professional engineers will ensure an all-encompassing, comprehensive service that, with appropriate maintenance, will protect your metal for fifty years or more. If you’re going to do the job, do it right, contact Armco Superlite.


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