Steel

Coloured Coated Steel

The construction industry is supported by the manufacture of high quality, competitive products and by expert technical service. Our service and quality commitment is based on a policy of working closely with our customers, applying quality assurance practices to all our activities, and achieving technical excellence through research, product development and capital investment. The extensive range of plastic coated steels available is a product of that commitment.



Steel as Profile Material
Steel, with its combination of flexibility, durability, strength-to-weight ratio and economy, is an ideal material for profiled cladding. To avoid the rapid corrosion of steel, a metal coating can be applied to protect it from moisture and oxygen. Such coatings need to be sufficiently impermeable, tough, abrasion resistant and must bond strongly to the surface they are required to protect. Coating steel with a zinc layer is called galvanization. There are many variants of galvanizing which can involve zinc alloys rather than pure zinc. Zinc coatings have excellent corrosion protection, because they protect the steel in two ways:

  • with a barrier effect
  • by cathodic protection

 

Barrier effect
The barrier effect is achieved by physically sealing off the steel surface with a coating with better corrosion resistance. The zinc layer itself forms a self-protecting film off airly impermeable corrosion products such as zinc oxide. This protects the steel (and the zinc) from the harmful affects of oxygen, corrosive gases and liquids in the atmosphere.

Cathodic protection
The second principle is cathodic protection. If the zinc coating is damaged (by weathering, pores, cracks, scratches, cut edges), then the anodic nature of zinc becomes effective in providing protection. Since zinc has a lower chemical potential than iron, the zinc will be attacked and dissolved first. The zinc dissolve to form zinc hydroxides and zinc oxides (white rust), which unlike iron oxides (red rust) form a protective layer, which slows down the corrosion process.

Options for galvanic protection
Galvalloy
Galvalloy is strip steel which has been hot-dip coated with a 255 g/m2 eutectic alloy comprising approximately 95% zinc with 5% aluminium, combined with other elements, to EN 10214:1995.

Hot-dip zinc
Hot-dip zinc coated steel with a total of 275 g/m2 of zinc, according to EN 10147:2000. This can be finished with a number of coatings – polyester, PVDF, Plastisol and Plastisol Foodsafe.

Galvatite
Galvatite is hot-dip zinc coated steel to EN 10147:2000 with a standard minimum coating mass
of 275 g/m2. A structural grade of steel with a guaranteed minimum yield strength of 280 N/mm2 is used for all
products. Substrate designations are:

  • Galvalloy – S280 GD+ZA according to EN 10214
  • Galvatite – S280 GD+Z according to EN 10147

 

Coated Products
The customer can be certain that each coating system has been comprehensively tested and evaluated in the extensive research and development facilities of our suppliers. These finishes have been developed over many years for a variety
of applications, and therefore have different performance characteristics. The descriptions that follow are aimed at distinguishing these differences. Coated products for exterior roofing and cladding are composed of a galvanised steel substrate which is then treated / primed on both sides. Different proprietary topcoats are then applied to the weather
side and to the reverse side (commonly referred to as the back-coat). Different galvanising systems and coating products are used for different applications.

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