Zinc is composed of very high quality zinc Z1 (99,995% zinc), as defined by the EN 1179 standard, to which titanium and copper
- Copper raises the mechanical resistance of the alloy making it harder and stronger. It also controls the colour of the natural protective patina that is created as the zinc weathers
- Titanium increases the creep resistance, permitting far greater thermal expansion and contraction of the material without causing metal fatigue
- Titanium: 0.06% minimum – 0.2% maximum
- Copper: 0.08% minimum – 1.0% maximum
- Aluminium: 0.015% minimum.
The Material & Finish’s
Zinc is an imported material, and generally is available and not carried as a stock item. In its original natural form it has colour
closely resembling that of plain aluminium. Over a period of time the zinc will start to patina, and change colour to a light grey.
This type of natural zinc is not commonly used in New Zealand.
Quartz-Zinc: is the mainly used material in New Zealand which is the natural product that has been through a surface treatment process that speeds up the patina effect, that generally would take’s years to achieve.
Anthra-Zinc: is the same base material but has under gone a coating process to give a charcoal black finish. The finish may slowly and gradually lighten over time to a dark grey.
Pigmento: is available in four colours, organic red, green, blue and brown. The colour is created by adding mineral pigments to the durably protective coating.
Zinc in compliance with BS EN 988: 1987 Zinc and Zinc alloys. Specification for roll flat products for buildings.
Available in 0.70mm.
Natural Zinc and Quartz-Zinc 600mm
Anthra-Zinc and Pigmento 600mm
The patina forms a layer which is compact, adherent, insoluble in rainwater, and which will hinder any further exchanges between oxygen and zinc, thereby controlling the corrosion rate and maintaining it at a low level. Nevertheless, the durability of zinc can be reduced by some acid pollutants, which increase the corrosion rate. The main pollutant is sulphur dioxide (SO2).
Sulphur dioxide reacts with the patina to form a sulphate (ZnSO3 + ZnSO4), which is soluble in water and is washed away by rain. Ongoing protection against corrosion requires oxygen to be available at the surface. Zinc can also suffer from corrosion when used in ways that prevent this, e.g. under ventilated skillion roof construction, continuously wet environments like end laps or under accumulated debris.
Regular washing with water and a soft brush is required every 4 – 6 months to maintain an unaffected surface for good aesthetic quality in industrial and marine environments. Particular attention is required in server marine locations and sheltered areas to prevent the build-up of salt or dirt deposits.