The coating that lasts
The coating for the Natural range of iron pipes consists of ZnAl 85/15 (Cu), and 85/15 Zinc-Aluminum alloy enriched with Copper, with a minimum mass of 400 g/m2 and a protective Aquacoat layer (80 µm thick on average).
The BioZinalium coating is composed of :
- a layer of zinc-aluminum 85/15 alloy enriched with Copper with a minimum mass of 400 g/m2, applied by spraying molten metal onto the cast iron surface, using an electric arc gun and ZnAl (Cu) alloy wire.
- a protective Aquacoat layer (semi-permeable) of an aqueous phase acrylic-PVDC type, 80 µm thick, applied by spray gun and blue in colour.
Protection against overall corrosion
The BioZinalium coating conserves the 'active' properties of the Zinalium coating when it is in contact with soil.
- Formation of a stable protective layer
In contact with the surrounding soil, the BioZinalium slowly turns into a dense, adherent, impermeable and continuous layer of insoluble zinc salts. This forms a protective screen. The presence of aluminum increases the passivation effect even in highly corrosive soils, reducing the zinc consumption rate. Whilst allowing galvanic protection and self-healing, the Aquacoat paint promotes the formation of a stable, insoluble layer of Zinalium conversion products.
- Damage self-healing
This mechanism is the first to occur. One of the features of the BioZinalium external coating is its ability to restore the continuity of the protective layer in small areas which have suffered local damage. The Zn++ ions migrate through the pore-sealer to heal the damage, then form stable, insoluble corrosion products.
Insurance against localized Biocorrosion
The enrichment of the ZnAl (Cu) alloy with Copper permits a reduction of the random risk of localized biocorrosion in the following situations :
- anaerobic soil (heavy soil, damp clays, etc.),
- soil rich in SO4²- sulphates and organic matter,
- damage to the coating.
BioZinalium therefore provides a brand new way of reducing this possible risk and thus increasing the guarantee of longevity.
Advantages of the 400 g/m² BioZinalium coating
The active nature of the metallic layer + the deposited surface mass + the properties of the final layer are three dimensions that contribute to the effectiveness of the BioZinalium coating.
Range of application
As for Zinalium, the BioZinalium-based coating makes it possible to :
- dispense with systematic BioZinalium soil surveys,
- cross corrosive sections without risk, with no need for additional protection using a polyethylene sleeve, and therefore with no extra work site cost,
- simplify the management of small diameter pipeline inventories.
BioZinalium complies with European standard EN545: 2010 and the international standard ISO 2531: 2009. The BioZinalium coating is suitable for most soil types, as defined in Appendix D.2.2 of standard EN545: 2010, with the exception of :
- soil with resistivity lower than 500 Ω.cm ;
- peaty, acidic soil ;
- soil containing waste, ash, slag, or contaminated by certain industrial waste products or effluents.