Cut edge corrosion

A continuous, factory controlled process in which paint is roller applied to coiled metal strip, cured in ovens and rewound before the strip is cut and formed into components. It is the basis of pre-finished steel and aluminium sheet used for roofing, cladding and rainwater goods.

A thick, usually embossed coating based on PVC dispersed in plasticiser, applied by coil coating over primed, galvanised steel used for profiled roofing and cladding sheets. It offers good formability and durability, but cut edges and mechanical damage need maintenance to prevent edge corrosion and peel back.

A coating that cures to a flexible, rubber-like film capable of bridging fine cracks and accommodating movement of the substrate. Acrylic, polyurethane and silicone based elastomeric coatings are widely used for liquid applied roof waterproofing and for the refurbishment of profiled metal roofs.

A chemical species that reduces the corrosion rate of a metal when present in relatively small amounts, either dosed into the surrounding environment, for example in cooling water systems, or incorporated as inhibitive pigments within a primer.

Steel or aluminium sheet cold roll-formed into trapezoidal, sinusoidal or other profiles to provide spanning stiffness, used as roof and wall cladding and as structural decking. Sheets are typically metallic-coated steel with a factory-applied organic coating, fixed through to purlins or rails, or used as the skins of built-up and composite panel systems.

Refurbishment of an existing roof by installing a new waterproofing or covering system over the retained build-up rather than stripping it, normally after a condition survey and condensation risk assessment. On profiled metal roofs the equivalent practice is called oversheeting, where new sheets are fixed over the old covering on spacer systems.