Avoiding galvanic/bimetallic corrosion between aluminium decking or balcony components and galvanised steelwork aluminium decking or balcony components and galvanised steelwork

One of the most common scenarios that AliDeck aluminium decking and balcony component products are used in is on steel-framed balconies, manufactured from galvanised steelwork.

With the two metals in close proximity once installed there is the risk that galvanic corrosion may occur unless suitable precautions are taken.

Galvanic corrosion (also known as bimetallic corrosion) is an electrochemical process that occurs when dissimilar metals are in contact via an electrolyte, with one of the metals corroding much more rapidly than if the two metals were not in electrical contact. An example of such a scenario would be aluminium connected to steel and doused in rainwater.

Breaking this contact, then, is key to preventing galvanic corrosion. Fortunately, AliDeck has several solutions for this problem;

AliDeck products are powder-coated to Qualicoat standards, ensuring a layer of highly durable powder-coat of 60-80 micron thickness is between the aluminium and any steel
AliDeck also supply a fire-resistant tape that can be used to provide a barrier layer between the aluminium and steel
The ratio of any fixings to the overall weight and surface area of the aluminium decking boards is such that this is not a realistic risk for introducing galvanic corrosion, but the use of rubber thermal washers on fixings could be used to minimise contact between the fixings and the boards and is an absolute recommendation when using self-drilling screws

Using Fire Resistant Tape as a barrier between aluminium pedestals and steel balcony framework

Another factor to consider is that steel used in architectural applications is commonly galvanised, which means that it is coated in a protective layer of zinc. When this is the case in scenarios where aluminium decking is to be installed, such as on a steel balcony, bimetallic corrosion is minimised due to the relative closeness of the anodic values of aluminium and zinc.

This zinc layer creates a barrier between the steelwork and the decking boards, not to mention the further barrier created by the powder-coat on our products. That said, it is still advised to take precautions as if the galvanisation on the steel is compromised, by drilling or cutting for example, then the steel could be exposed to electrical contact with the aluminium.

In conclusion, galvanic corrosion is a serious concern and poses a genuine commercial risk to developers, constructors, and building owners but there are practical and positive steps that can be taken to minimise this risk when using our aluminium components on steel framework.