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External Protection System

Zinc Coating

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 :

  1. As per customer requirement 400 gm/m2 Zinc Alloy (for very corrosive soil)

Epoxy Coating

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

Polyurethane coating

Electrosteel offers pipes with External Polyurethane coating as per EN 15189 for heavy duty Corrosion protection in highly aggressive soil.

 

Polyethylene Sleeving

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.

PE Tape wrapping

The PE tape with approved adhesive is applied on the Ductile Iron Pipe over a bitumen based primer, with 25 mm overlap on itself or 55% overlap.

  • Mechanically applied Plastic Tape ensures that the inert PE tape is wrapped tightly and uniformly over the pipe surface
  • In comparison to PU Coating, which is only 700 micron ( less than 1mm thick)  the PE tape is 1.5 mm thick i.e more than double of the PU thickness.
  • Plastic tape offers a thick, inert , holiday free barrier between the soil and the Pipe.
  • No risk of soil entrapment between the Tape and the pipe surface.
  • For Plastic tape wrapping at joints special care is taken to cover the joint after jointing is done. Special filler materials are placed at the joint to smoothen the diameter change between the spigot and socket over which the tape is wrapped. The joint remains flexible but at the same time fully protected.