How long do roofing screws actually last on a roof without rusting? How quickly do roofing screws drill through? The corrosion resistance of KINGI® screws and other screws available on the market has been tested at independent expert institutions using the most demanding possible tests. Tests have also been conducted on the screws’ drilling performance and coating thicknesses. All test reports can be read in full – draw your own conclusion.
Over 20 years of Finnish climate compressed into 1,000 hours.
The Thin Sheet Centre of Häme University of Applied Sciences tested eight roofing screws commonly sold in Finland in a 1,000-hour prohesion test. The test stress corresponds to over 20 years of actual climate stress under Finnish conditions – in practice, it is the typical service life of an entire steel roof before the first maintenance painting.
Based on the tests, KINGI® is suitable for use in conditions with a corrosivity category of C4 and where a high durability class (H) is required. This covers Finland’s coastal areas and industrial climate environments – precisely the places where the choice of roofing screws determines the service life of the roof. The corrosion resistance of Kingi screws has also been tested in accordance with the new EAD’s corrosion tests, and the result there too is a European Technical Assessment (ETA-25/0267) for class C4.
In addition to HAMK’s 1,000-hour test, we commissioned three detailed comparative tests. They examine roofing screws from two perspectives: durability, that is, coating thickness and its corrosion resistance, and installability, that is, the drillability of the tip. Together, these tests provide an overall picture of why there are such significant differences in quality between roofing screws.
Coating thickness
If the paint coating on a roofing screw lasts, the roofing screw will also last without rusting. A correctly applied, sufficiently thick coating protects the screw from corrosion. The test measured the coating thicknesses of different roofing screws and assessed their durability in practice.
Corrosion resistance
Roofing screws are exposed to harsh weather conditions. The test examined how the paint coating of seven different roofing screws withstands challenging corrosion conditions, and what happens to the steel underneath when the coating is damaged.
Drilling performance
A good roofing screw drills through the thin steel sheet being fastened quickly and accurately without scratching the roofing sheet. The comparison included 10 different roofing screws – the results show how significant the differences actually are.
Qualisteelcoat is an independent European testing body that specialises specifically in paint coatings for steel. It sets strict requirements for the durability of coatings and grants approval only to tested coating material combinations, without relying on the manufacturer’s own claims.
Qualisteelcoat has granted approval for the coating material combination used in KINGI® for climatic corrosion category C4 (H) – severe climatic exposure and its highest durability class. The same classification has also been confirmed by two other independent methods: HAMK’s Sheet Metal Centre’s 1,000-hour prohesion test and the official European Technical Assessment (ETA-25/0267). Three independent bodies have therefore reached the same result using three different methods, which is exceptionally strong evidence of the durability of the painted carbon steel roofing screw.