Hot-dip galvanized fasteners

Hot-dip galvanized fasteners

Hot-dip galvanizing – bolts, screws, nuts, washers, etc. with the coating made by the hot-dip galvanizing method. Hot-dip galvanizing is widely used in fastener manufacturing as it prevents corrosion by offering barrier and galvanic protection to the base steel.

To be galvanized, fasteners are completely immersed in a molten zinc bathand held there until the temperature of steel equilibrates with that of the bath (complete immersion into molten zinc ensures excellent corrosion protection).The steel is cooled in a quench tank to reduce its temperature and inhibit undesirable reactions of the newly formed coating with the atmosphere.

The surface protective layer of molten zinc (from 30 to 60 µm) is resistant to shearing distortion, mechanical deformations and strokes. It guarantees cathodic protection to the base steel even after damage.Hot-dip galvanizing coating ensures long-term and maintenance free corrosion protection for more than 50 years.Average thickness of the galvanized coating 20-40 μm.

  • When fasteners are manufactured for further hot-dip galvanization at the BERVEL GmbH plants, metric threads are loosened according to the coating thickness (20-40μm). In addition, further treatment of products for galvanization completely eliminates the acid etching operation, preventing further hydrogen embrittlement, etching of the steel base and as a consequence, destruction of the product under high loads. This operation is replaced by mechanical treatment of the surface.
  • Galvanization of products is performed only in melted zinc of the 1st category, i.e. maximum treated zinc, which provides a completely even final surface to the products, withoutany  impurities and inclusions.
  • Nuts are also manufactured with a loosened thread, undergo the same treatment, are galvanized, and then the final thread cutting is performed according to strict parameters specified in the standards. These operations preserve the zinc coating at the internal thread and provide matching with bolts.