Due to the compression ability of paint, galvanising coating and other types of surface protection, it is required that places of joints for high-strength structural bolting assemblies for preloading are cleaned from any coating before installation. After the installation process, depending on the type of coating of the assemblies, the whole surface can be further covered to restore corrosion protection in joint places.
Please refer to EN 1090-2:2018 pt. 8.4 - Preparation of contact surfaces in slip-resistant connections and the precautions that need to be taken before the assembly:
- the contact surfaces shall be free from all contaminants, such as oil, dirt or paint. Burrs that would prevent solid seating of the connecting parts shall be removed;
- uncoated surfaces shall be freed from all films of rust and other loose material. Care shall be taken not to damage or smooth the roughened surface. Untreated areas around the perimeter of the tightened connection shall be left untreated until any inspection of the connection has been completed;
- thick surface coatings should not be present between washers and connected surfaces.