For any major building project, there are several factors that may play a role in longevity. UV exposure, mechanical damage and several others are all important elements here, but one that’s commonly overlooked is known as galvanic corrosion.
At QC Facades, we’re happy to explain corrosion risk factors to you for any of our rainscreen façade materials, from our honeycomb façade to our glass rainscreen and many others. Galvanic corrosion, also called bi-metallic material corrosion, can occur when two metals that are not similar come into contact with each other through a few different formats. Let’s look at some important factors to understand here, plus some tips on avoiding galvanic corrosion on any of our façade materials.
Galvanic Corrosion Basics and Causes
When two dissimilar metals are used in nearby areas, galvanic corrosion can take place when small electric currents, plus the presence of moisture and oxygen between the metals, leads to the more anodic of these metals corroding. In this case, the less anodic metal (called the “noble” metal) will not be affected. If you are using steel pipe along with brass fittings, for instance, the steel will corrode first due to being lower on the galvanic series (more on this in a moment).
Now, understand that the simple use of two different metals during building construction does not automatically lead to corrosion. There are some simple steps you can take to prevent this, which we’ll go over below. It’s also important to note, however, that metals don’t have to make physical contact for this corrosion to occur – when a noble metal corrodes even slightly and dissolves in rainwater, this material can flow to a less noble metal and corrode it as well. An example of this is when a roof or window surround is made from a different metal as the façade cladding.
Galvanic Series and Façade Elements
We mentioned the galvanic series above – this is a general ranking of which metals are more anodic and less anodic. The further apart metals are on this scale, the larger the chance of galvanic corrosion on the less noble metal. Some examples of façade metals that are less noble, and therefore highly susceptible to galvanic corrosion, include:
- Zinc and zinc alloys
- Aluminum and aluminum alloys
- Mild steel
Façade metals that are closer to the middle of the corrosion risk spectrum include:
- Aluminum bronze
Finally, metals like stainless steel type 304 and 316 are highly noble, and therefore not at great risk of corrosion.
Corrosion Avoidance Tips
Some general tips for avoiding galvanic corrosion issues on your rainscreen façade materials:
- Choose metal materials that are close together on the galvanic series.
- For metals further apart on the series, insulate each from the other to break any electrical connection.
- In addition, separate the two metals with an inert spacer.
- Apply coatings to one or both metal materials to protect from corrosion.
- Add a specific corrosion inhibitor.
For more on avoiding galvanic corrosion on your façade materials, or to learn about any of our composite, aluminum or other rainscreen products, speak to the staff at QC Facades today.