Cut Edge Corrosion Damaging Your Roofing System?

Corrugated metal sheets are not limited to agricultural buildings, in recent years there has been a significant rise of this material being specified in the commercial and industrial sector. It is fair to say that cut edge corrosion will affect these sheets at some point during its life cycle.

 

What is Cut Edge Corrosion?

Cut edge corrosion describes the breakdown of the coating to the cut edge on metal sheeting which, when exposed to the elements can cause corrosion.

When the sheets are manufactured, the corrugated sheets are usually coated in Plastisol or PVF2. This coating protects the metal substrate and improves its appearance. When the sheets are cut to size, the edges are often not re-coated and left exposed.

Over time this edge is exposed to the elements. Consequently, the factory coating peels away from these edges, exposing the substrate which is susceptible to corrosion which is exacerbated by water, oxygen, and pollutants.

Any metal edge may be vulnerable, so cut edge corrosion is usually found on the edges of sheets where they overlap one another and at the eaves. The horizontal laps are particularly vulnerable to this type of deterioration.


How to Repair Cut Edge Corrosion

Treating cut edge corrosion is essentially very easy if caught early enough, the biggest constraint we have when treating it is the weather, the surface has to be bone dry.

Cut Edge Corrosion
Cut Edge Corrosion Roof

 

1) Inspect the sheets for the extent of the corrosion and carry out an adherence test. Sometimes a degreaser is needed.

 

2) Clean sheets and remove all loose/flaky rust and plastisol, feathering in the edges of the plastisol. This can be achieved using wire brushes, mechanically or with vapour blasting equipment.

 

3) Apply one coat or Corrosion primer, applied to a wet film thickness of 160 microns. Wait 24 hours to cure.

 

4) Apply one coat of Flexlap polymer finish, applied to a wet film thickness of 250-300 microns.


When inspecting a roof and you come across existing coatings/treatments and delamination like the pictures below; additional preparation is required and in some cases, replacement or over cladding may be the only option.

We are the industry leaders in this area. Liquasil team of chartered building surveyors & chemists will be able to assist you.

[Article posted by Harry Street @ Liquasil]

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