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Does Aluminium React with Galvanised Steel?

Published by Lucy Thurston on

Aluminium and galvanised sheet metal are integral materials in the construction industry, meaning that it would now be difficult to imagine a life without them. Despite this, an aluminium sheet and a galvanised steel sheet cut to size are sure to react with one another due to their dissimilarities.

Although aluminium is resistant to environmental influences, it can fall victim to contact corrosion upon interacting with dissimilar metals such as galvanised steel. This is because dissimilar metals have different electrode potentials in which the aluminium will act as the cathode, and the galvanised steel will become the anode, resulting in a chemical reaction and a corroded appearance.

What is Aluminium?

Aluminium is an element on the periodic table and is one of the most widespread metals on Earth. In fact, aluminium accounts for eight percent of the Earth’s core mass and is the third most common chemical element on the planet. Similarly, aluminium binds well with other elements in the forming of compounds.

Curved Aluminium Sheets

In What Areas is Aluminium Used?

Aluminium is used in various production areas, such s the construction of houses, supermarkets, shops, ships, and aircrafts. Despite this, we also come across many aluminium objects in day-to-day life. For instance, foil in the food industry, cooling elements for radiators, pipes, cables, bushings, and manufacturing materials are all crafted from aluminium.

Additionally, there are traces of aluminium in the likes of wheat, rice, and peas, whilst aluminium can also be used in the manufacturing of dishes. With this being said, it’s vital that acidic food isn’t cooked in these dishes, as this can result in a chemical reaction, enabling the aluminium to enter the food. Ultimately, aluminium has many applications, but it will corrode via improper use.

What is Galvanised Steel?

Galvanising refers to the coating of steel with zinc. This process is administered to inhibit rust from occurring, meaning that galvanisation successfully provides long-term protection for steel products.

In What Areas is Galvanised Steel Used?

Most commonly, the galvanised steel sheet specifications make it ideal for applications in ductwork, HVAC equipment, and construction. This is due to its rust-resistant and durable nature, which makes it ideal for outdoor industrial use.

Understanding the Galvanic Corrosion Process

Galvanic corrosion refers to the process in which two dissimilar metals hit, as different electrochemical properties meet under the influence of an electrolyte film, corrosive environment, and electrolytic liquid. During this process, the metals undergo a chemical reaction with electrolytes, which creates a cell. As a result, one metal is corroded at the expense of another.

The Galvanic Corrosion Process

The electrode potential of each material is unique, and the difference between them creates an electrical current for metals. This is because the material with positively charged particles moves to the material with negatively charged particles. If the negatively charged material forms a more active metal, the positively charged metal will adjust accordingly to become less active. Consequently, the negatively charged metal corrodes faster, whilst the positively charged metal may not change at all.

What Does Galvanised Corrosion Look Like?

Galvanic corrosion results in the destruction of the crystal lattice at the molecular level, which leads to a distinguishable appearance. This appearance adheres to various features, including:

  • A uniform character
  • A lack of spreading across the surface
  • Deep craters, holes, and depressions
  • A direct location of where the aluminium came into contact with galvanised steel
  • A localised area

In order for the galvanic corrosion of aluminium to take place, certain conditions must occur. These conditions include:

  • Exposure to aggressive environments
  • Exposure to an electric current
  • Contact with other materials
  • The presence of an electrolyte

How Aluminium Corrodes with Galvanised Steel

Galvanised steel is steel that has been coated in zinc, and zinc is more electronegative than aluminium. When connecting an aluminium sheet with galvanised steel fasteners, the crystal lattice of the metal will be destructed. This leads to the spoiling of the aesthetics of the galvanised fasteners, which, in turn, will damage the aluminium sheet.

How to Protect Aluminium from Corrosion

In order to protect aluminium from corrosion, rigid anodes will need to be used. It’s worth noting that corrosion not only occurs in water but in chemical sediment, as well as moist air and soil. When it comes to protecting aluminium materials from corrosive conditions, it’s important to inhibit the electrical current from passing through as much as possible. Pairing aluminium with the correct metals allows for a longer lifespan of the object or structure.

Does Aluminium React with Galvanised Steel?

Buy Galvanised Steel Sheets from Rapid Metals

As galvanised steel sheet suppliers in the UK, we provide a multitude of galvanised steel sheet sizes and galvanised steel sheet thicknesses. We keep our galvanised steel sheet costs low so that you can fulfil all your metal needs with ease. Contact us here at Rapid Metals to discover more about our product range.

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Does Aluminium React with Galvanised Steel?

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