What Is Reverse Cut Edge Corrosion And How Is It Treated?

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This is a sub-article of our What Is Cut Edge Corrosion And How Is It Treated article.

Here we investigate an issue that can occur after treating cut edge corrosion, called reverse cut edge corrosion.

But, what is it? How does it occur? What are the dangers associated with it? How do you treat it? And can you prevent it from occurring?

What Is Reverse Cut Edge Corrosion?

Reverse cut edge corrosion happens when a treatment is applied to normal cut edge corrosion to repair it.

But, due to a fault in the application, water condenses on the underside of the sheet, corroding it. This is a serious issue and has to be dealt with as soon as it’s discovered as the sheet can collapse in on itself.

How Does Reverse Cut Edge Corrosion Occur?

If the treatment used to prevent cut edge corrosion isn’t breathable, condensation can occur on the underside of the sheeting.

Liquid will then collect above the cut edge sealed joint detail and reflux as the sheeting is heated and cooled by sunlight.

This causes corrosion to occur on the reverse side of the sheeting.

Once this happens it can, in some cases, become impossible to treat due to a lack of access to the reverse of the sheet.

There are three things to look out for when checking for reverse cut edge corrosion:

  1. The existing repair has rust staining that is weeping
  2. Corrosion blisters in the sheeting above the joint
  3. The sheet itself is visibly corroded

What Are The Dangers Associated With Reverse Cut Edge Corrosion?

If any of the above are observed, there is a significant danger posed by the roof.

It should not be approached as the sheeting may collapse due to under loading.

How Do You Treat Reverse Cut Edge Corrosion?

Depending on your chosen manufacturer there are products that can be used to help alleviate the condition.

However, care must be taken as your warranty may be voided if the treatment is not approved by your manufacturer.

Can You Prevent Reverse Cut Edge Corrosion From Occurring?

Preventing reverse cut edge corrosion is very similar to normal cut edge corrosion in that steps can be taken to slow, or avoid, it occurring.

Regular maintenance is vital for preventing reverse cut edge corrosion as we’ve mentioned previously, as any build-up can greatly increase the rate at which the corrosion spreads.


While reverse cut edge corrosion is a very serious problem for a roof, if regular maintenance of the roof is undertaken, it is less likely to occur.

As we’ve spoken about before, regular maintenance of a roof greatly extends its lifespan as well as lowers the costs of repairs by either eliminating a problem before it occurs or catching it early.

If you have a roof that you’re worried may be suffering from reverse cut edge corrosion, or if you’re looking to schedule regular maintenance for your commercial roof, contact us today.

This article, as with all other articles we produce, is for guidance purposes only. It does not constitute formal advice and should not be relied upon as such. For bespoke, unbiased advice relating to your commercial roofing project please contact us and we would be pleased to assist.

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