External Protection System
The Zinc coating consists of a metallic Zinc alloy layer applied by metallization on the pipe surface. The metallic Zinc coating is covered by a finishing layer of a bituminous product or synthetic resin compatible with zinc. An improved chemical and mechanical stability of the coating is provided by the zinc coating and the finishing layer.
The International Standard ISO 8179 establishes the main features of Zinc coating as well as suitable methods for checking them. Zinc coating is applied in varying thickness depening on soil aggressivity. The options are :
- Standard 130 gm/ m2 and finishing layer of 70 microns
- 150 gm/m2 and finishing layer of 70 microns
- 200 gm/m2 and finishing layer of 70 microns
- 400 gm/m2 and finishing layer of 70 microns
In case of Fittings normally Zinc rich paint coating is applied instead of metallic Zinc coating
Zinc Alloy Coating
For corrosive soil environment, Electrosteel has developed a patented process of Zinc alloy coating which consists of a metallic Zinc alloy layer applied by metallization on the pipe surface. The metallic Zinc Alloy covered by a finishing layer of a bituminous product or synthetic resin compatible with zinc. An improved chemical and mechanical stability of the coating is provided by the Zinc alloy coating. The options are :
- As per customer requirement 200 gm/m2 and finishing layer of 70 microns
- As per customer requirement 400 gm/m2 Zinc Alloy (for very corrosive soil)
Compared to normal bitumen coated pipes it offers:
- More resistance to external galvanic/ soil corrosion in aggressive soil
- More resistance to external chemical (acid, alkali, organic) attack
- Better adherence to metal surface, hence more durable coating
- Higher scratch resistance
- Good resistance to coating damage during transportation/ handling/laying
- Comes in attractive blue/green (for water) or red ( for sewerage) colour
Electrosteel offers pipes with External Polyurethane coating as per EN 15189 for heavy duty Corrosion protection in highly aggressive soil.
Loose polyethylene encasement is found to be very effective for protection of Ductile Iron Pipes and Fittings in corrosive environments and widely practiced in USA, Europe and Australia, instead of Zinc coating. Investigation of many field installations, where loose polyethylene encasement has been used as protection for Cast Iron and Ductile Iron pipelines indicates that polyethylene encasement provides, for even highly corrosive test sites, a high degree of protection. The dielectric capability of polyethylene provides shielding for Ductile Iron Pipes and Fittings from stray direct current encountered in the field. When Ductile Iron Pipes are layered with P.E. sleeving, the fittings are also covered with P.E. Sleeving.