Zinc Coated Structural Screws for Corrosion Resistance

Structural screws are vital elements in ensuring the strength and integrity of buildings and various other structures. They are often required to withstand heavy loads and so are frequently made from carbon steel due to its great strength, which results from the heat treatment to which it is subjected during the manufacturing process.

Carbon steel, however, can suffer from corrosion if exposed to various factors such as contaminants that include salt, water or extremes of temperature. To ensure the strength of structural steel is not degraded, protective coatings are applied to reduce or eliminate the risk of corrosion.

Corrosion Protection Through Zinc Coating

One of the most commonly used and effective methods of corrosion protection for structural screws for load bearing projects is zinc coating. This applies an extra layer over the metal, which acts as a protective barrier that separates the metal from contaminants and also as a sacrificial coating that will corrode before the metal underneath. These are available from a wholesaler screw supplier.

Different zinc coating processes are available and have varying characteristics:

• Zinc electroplating applies a thin coating of zinc using an electrolyte. Post-plating treatments can add further protective layers, including heat treatment that reduces the risk of part failure.

• Mechanical zinc plating uses a tumbling process with glass beads to coat the screws with zinc powder. This method is suitable for simple components and similar post-plating treatments are available.

• Zinc flake coatings are applied with aluminium flakes as a liquid using a dipping process but are not suitable for very small screws. A top coat can be added for a better appearance and added protection.

• Hot dip galvanising is used where screws are dipped in molten zinc and the excess is removed by centrifugal force. The zinc coating is thicker and longer lasting but is not suitable for small thread screws.

Choosing the Most Suitable Corrosion Resistant Coatings

The type of coating that is best for you will depend on several factors. These include:

• The type of application where the screw is being used and the importance of the connection being made.

• Whether the screw is being used in a dry, internal environment or if there is moisture that can cause corrosion and ultimate failure.

• If the screws are for a structure in a coastal environment where there is salt in the air and high humidity levels.

• If chemicals are present and these provide challenges for the screws and their protective coating.

In essence, the coating that is required often depends on the level of resistance to corrosion that is needed. Electroplated clear zinc on low carbon stainless steel is adequate where relatively low corrosion resistance is needed but hot dipped or mechanically applied zinc is better for medium resistance. Higher grade steels (types 304 and 305) give high resistance while severe corrosion threats require type 316 stainless steel, which can be sourced from a stainless steel fastener supplier, that is hot dip galvanised.

If you are not sure of the protective coating you need for structural screws, contact us and we will advise you of the most suitable types. We have a large range available here at Bricon Industries and can supply the perfect screws for any job.