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Galvanic Corrosion

Galvanic corrosion occurs when two different metals oxidise and corrode by an electrolyte such as water. Galvanic corrosion is the reason why contact between two different types of metals should always be avoided.

However, there are three circumstances that must be met in order for this type of corrosion to occur;

  1. There must be two different types of materials
  2. The metals must be in contact with each other
  3. They must be subject to an electrolyte [1]

If these three conditions are met then there is a very high likelihood that corrosion will occur. The severity of the corrosion is dependant on the types of metals that are coupled together.  The galvanic chart below shows the nobility of metals. The farther apart the metals are from each other on this chart, the greater the corrosion that occurs. [2]

The typical old ‘Queenslander’ houses tend to be fitted with galvanised roofing materials when originally constructed. However, many more modern homes now use Colourbond & Zincalume roofing. The old galvanised roofing is compatible with lead flashings; however, these newer roof types are not due to their metallic coatings. [3]BlueScope steel states that if building design is such that water will flow from lead flashing onto this roof type then it  should be painted. [4]

Pictured below is an example of galvanic corrosion occurring due to two different metals found by Brisbane Roofing Solutions upon a roof inspection. The corrosion is due to one metal being Cathodic (Zincalume) and one being Anodic (Galvanised) being in contact with each other. The Zincalume tends to be protected but the Galvanised suffers great corrosion very quickly.

Galvanic corrosion is also something to consider prior to installing solar panels. This occurs when the aluminium frame or the brackets used to join the panels has corroded slightly, flowed below and dissolved onto the galvanised roof. There it has re-deposited on the galvanised iron roof which leads to corrosion and inevitable problems in the future.

If your roof is currently showing signs of corrosion, a roof restoration may be able to salvage the current roof and save you from a costly roof replacement. This is done by pressure cleaning, applying a rust inhibitor (e.g Penatrol) to treat existing surface rust, followed by 1 coat of metal primer, and 2 coats of Globalcote Elastacote Acrylic Membrane Roof Coating to prevent and stop any further corrosion. An inspection is advisable on these old roofs to determine whether the roof is worth restoring or a new roof is required.

Another option that is available that may be of some interest is the use of polycarbonate sheeting in some situations e.g. patio roofs etc. The polycarbonate sheeting used by Brisbane Roofing Solutions comes in Clear, Opal, Bronze & Grey. These sheets let light in whilst also reflecting away some heat (see chart below for details). These are a good option as well as they are not subject to galvanic corrosion.

Colour Light Reflection Heat Reflection
Clear 90% 0%
Opal 30% 61%
Bronze 38% 33%
Grey 20% 46%

If you suspect your roof is suffering from galvanic corrosion or you would like your roof inspected contact Brisbane Roofing Solutions today!

[1] http://www.anzor.com.au/blog/galvanic-corrosion-keep-those-metals-apart/

[2] https://gartalk.garlandco.com/understanding-galvanic-corrosion-and-how-to-avoid-it-in-metal-roofing/

[3] https://www.ambrosebuilding.com.au/insurance-repairs/dissimilar-metal-roof-sheeting-galvanic-corrosion/

[4] http://www.bluescopesteel.com.au/howto/avoid-incompatible-metals

 

Outstanding service all around, I can't recommend these folks enough if you need anything done to your roof.

Their communication was top notch, every worker was friendly, helpful and prompt, and all for a very reasonable price a roof restoration. I wish they would branch out into other trades, we'd use them again in a heartbeat!
Response from the owner:Thank You. We very much appreciate your business and taking the time to,leave a review. Cheers Jim and team😊
Brisbane Roofing did a small job for us in replacing on old whirlybird, they communicated well with us regarding timings etc and were very reasonably priced. Would definitely recommend and use again if we needed to.
Response from the owner:Thank You Leanne we appreciate your business and taking the time to leave a review. Regards Jim and team👍
The team couldn't have been better. Great communication, reasonable prices and timing to do the job. Turned up on time and ready, completed quickly and cleaned up afterwards, exactly how it should be.
Many thanks, have already recommended to friends needing roofing work.
Response from the owner:Thank You. We appreciate your business and taking the time to,leave a review. Regards Jim and team👍
✅Highly recommend these guys
They’ve done a fantastic job on my roof 👌👌👌
Response from the owner:Thanks Mori. We appreciate your business and taking the time to leave a review. Cheers Jim and Team👍
Jim, Sharon, and the team at Brisbane Roofing Solutions provided exceptional service. They worked closely with us to achieve the exact outcome we desired, and once the job was done, they left the area spotless with no overspray whatsoever. Their communication was excellent, they were organized and punctual, and they delivered high-quality work. It's been eight months since our roof was painted, and it still looks brand new. It's refreshing to see companies like theirs thriving today. I wholeheartedly recommend Brisbane Roofing Solutions
Response from the owner:Thanks Christine we very much appreciate your business and taking the time to leave a review. Cheers Jim and Team👍
So happy with our restoration and the issues that have been fixed. The process has been very easy for us and I love looking at our new colour every time I pull into the driveway. Thanks team!
Response from the owner:Thank You Kurt we appreciate your business and taking the time to leave a review. Regards Jim and team👍
The team offered very prompt & friendly service from the initial contact until completing the job. They did an amazing job on restoring our roof & we would highly recommend them.
Response from the owner:Thank You Sandra we appreciate your business and taking the time to leave a review. Regards Jim and team👍
Our roof restoration looks great!!! Great value for money, great communicators and everything done in a timely, professional manner. Will definitely use these guys again!
Response from the owner:Thank You Chenoa! We appreciate your business and taking the time to leave a review. Regards Jim and Team😊
Repeat client of Brisbane Roofing Solutions. The roof repairs and restoration, was completed by the team during a very hot week and I couldn't be more pleased with the results (and relieved given the wild storms!)
Thank you to James and his team for their great work - excellent result. Highly recommend this company. Anna D
Response from the owner:Thank You Anna we very much appreciate your repeat business and taking the time to leave a review. Cheers Jim and Team👍
Brisbane Roofing Solutions did an amazing job renovating our roof for the second time - the first time was over 10 years ago, and most of the repairs they made then were still perfectly intact. We had some issues with one part of the roof, but not only did Jim stand by his reputation, he paid to get the issue replaced! Not many businesses would be prepared to do that, great to see the integrity and dedication to reputation exhibited by this great Aussie Small Business. Not only do I highly recommend Brisbane Roofing Solutions, but you would be crazy to look anywhere else! Thanks, Jim & Sharron!
Response from the owner:Thanks Stephen we very much appreciate your repeat business and taking the time to leave a review. Regards Jim and team👍