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Profiled Metal Roofing & Cladding
Coating Failure and Cut Edge Corrosion
Problem: Coating Failure
The lifetime of a coated steel sheet may be defined as the time it takes to reach the stage where re-coating is necessary to preserve its performance or aesthetics and can be predicted using manufacturers’ projected performance data. It can be seen when the coating starts to fade, craze and/or delaminate or, on smooth finish coatings, when it starts to blister and spot corrode.
Some of the main reasons for coating failure are as follows:
- UV exposure makes paint hard and brittle limiting its ability to expand and c contact with the substrate, affecting adhesion & causing it to delaminate.
- Moisture laying on the surface can penetrate a coating causing d discolouration, lifting and corrosion on a steel substrate.
- Important pigments added for colour, UV stability etc. are lost through c chalking, a natural self-cleaning process where paint literally wears away.
The good news is that it’s usually the coating and not the sheet itself that needs replacing. Caught in time, most roofing and cladding can be treated and its protection indefinitely preserved.
Treatment: Delcote® Architectural Coating
Delcote® is a silicone system for reinstating long-term protective coating on profiled metal sheets with natural properties which can often provide better protection than the original coating for the following reasons:
- Silicones are highly UV resistant and stable from -100oC to +250oC
- Delcote® remains flexible and can easily accommode sheet movement.
- Delcote® repels water, preventing moisture from laying on the surface
- Delcote® is not self cleaning and will not sacrificially erode.
- Silicones form an insulating oxygen-free bond to steel.
- Delcote® forms a natural primerless anti-corrosion membrane.
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Benefits:
Delcote® requires little preparation and provides 200 micron protection at least comparable with Plastisol. Delcote® is applied as a system on roofs, incorporating Seamsil® to seal laps, bolts & cut edges. This, ensures that, unlike conventional coatings, the weakest details are equally protected.
Read more about Delcote Architectural Coating ®
Problem: Cut Edge Corrosion
Corrosion commonly starts as edge peel at the cut edges of a metal sheet. It develops through normal weathering mainly at overlaps and eaves and accelerates through capillary water held in the lap.
Edge corrosion is a progressive problem and, if neglected, can develop away from the cut edge, destroying the weather-sealed lap joint and gutter overhang. Early detection and effective treatment prevents costly future sheet replacement.
Treatment: Seamsil® 100
Seamsil® is the patented low modulus silicone system developed by Delvemade Limited in conjunction with GE Silicones to solve the problem of Cut Edge Corrosion. Seamsil® provides a strong, flexible external joint that can be installed without disturbing existing fixings and sheets. Its tenacious adhesion is unaffected by UV or weather and temperature extremes.
Benefits:
The Seamsil® system has been developed against a background of decades of experience of roof repair and is designed to be user friendly in application, comprising a gun applied sealant followed by a coating of brush applied Basecoat and coloured Topcoat.
Its built in simplicity makes Seamsil® a cost effective and reliable cure for edge and overlap corrosion problems and since 1993 has been the only system specified by the steel manufacturers for the treatment of cut edge corrosion.