Why is a three-layer coating the best guarantee for roofing screws?
Is your current or future roof made of Finland’s most popular roofing material, namely paint-coated steel?
By the start of the 21st century, the corrosion resistance of painted roofing sheets had increased to over 50 years and the maintenance interval to over 20 years, thanks to the Pural® coating developed in Finland. This development work was necessary to ensure that roofing sheets meeting Finnish requirements were available for use on Finnish roofs. All painted roofing sheets are made of triple-coated carbon steel and are sold under many different brand names.
When discussing the durability of a metal roof, the roofing screw is, unfortunately, all too often overlooked, even though it plays a vital role in the longevity of the entire roof and in maintaining the validity of warranties. This oversight is understandable, as buyers of a durable roof take it for granted that the roof will also be installed using equally durable roofing screws. This is not always the case, even though Finnish building regulations require it; roofing sheets must be fastened with roofing screws that have equivalent corrosion resistance (installation standard SFS EN 1090-2). Since 2015, when the triple-coated KINGI® roofing screw was launched, a matching fastening solution has been available for steel roofs.
Why do single-layer coated screws rust?
There are no shortcuts when it comes to rust protection for steel products installed on roofs. Electro-galvanising and a single thin coat of paint without pre-treatment do not provide sufficient protection for steel products intended for outdoor use. With this type of coating, roofing screws will not withstand installation and will rust away on the roof long before the roofing sheet itself. Unfortunately, these roofing screws are sold for outdoor use without justification. The only completely reliable indicator of a roofing screw’s suitability is the crown head. Only this guarantees that the screw has a triple-layer coating.
The three-layer coating guarantees rust resistance
The three-layer coating process used for KINGI® roofing screws is patented and was developed by Jorma Kinnunen, M.Sc. (Eng.), who has carried out pioneering development work to enhance the corrosion resistance of steel roofs. Screws intended for outdoor use must have an adhesion layer (pre-treatment), a primer and a topcoat on top of the zinc layer. This is the case only with KINGI® roofing screws. Sharper corners on steel structures require a thinner coat of paint than flat surfaces. According to painting standards, sharp corners and edges must be rounded off, which is why this has been done for KINGI® roofing screws. This ensures there is sufficient coating at every point. The adhesion of the coating is guaranteed by a special silane bonding layer, whose chemical bonds anchor the primer to the substrate. The two layers of powder coating total 120 micrometres, which provides sufficient protection even against C4 climate exposure.
When you’re ordering a new steel roof or having an old one repaired, it’s worth remembering that the cheapest part of the package is the roofing screw. A roofing screw can either ruin your roof or ensure it lasts for years to come. Only accept a three-layer coating. You can only obtain KINGI® roofing screws with a three-layer coating for your roof from our authorised dealers.