Surface Coating

Unprotected steel will inevitably corrode or as generally stated rust. One of the most commonly used and effective treatments to prevent corrosion is to coat the surface of the steel with zinc.

Zinc will form a stable surface layer of zinc oxide (white rust) which seals the surface preventing further corrosion. Should the surface suffer minor damage, the zinc coating will effectively ‘heal’ Itself.

The two most popular techniques for applying zinc to the surface of steel are:-

  • Zinc plating – also known as electrogalvanizing
  • Hot dip galvanizing

Both techniques commence with the removal of the surface layer of iron oxide (mill scale and/or rust) from the product followed by:-

Zinc plating. The product to be coated is immersed in a tank containing a solution of zinc salts. The zinc coating is electrodeposited onto the surface of the steel.

After zinc plating the zinc coating is generally passivated to increase the protective value of the coating.

To minimise the potential for the zinc plated product to fail due to hydrogen embrittiement (hydrogen can migrate into the product during the plating process) it is good practice to ‘bake the product which liberates the hydrogen.

Hot dip galvanizing. The product to be coated is immersed in a heated tank containing liquid zinc at approximately 450°C. A zinc-iron alloy layer forms on the product surface which bonds the outer layer of zinc to the product.

G.B. Steels will be pleased to arrange for your steel requirement to be surface coated.

We use the services of a subcontractor to offer bar which has been zinc plated, zinc plated and passivated or galvanized.