Coatings

Several different generic types of exterior primers for pipe and fittings are available upon request. Because of variables and complexities involved in the selection and application of a proper coating for a given service, AMERICAN invites inquiries for technical assistance.

ASPHALTIC COATING

AMERICAN furnishes most pipe and fittings coated outside with an asphaltic coating approximately one mil thick per AWWA C151 for ductile iron pipe, AWWA C115 for flanged pipe and AWWA C110 and C153 for fittings.

All across the United States ductile iron and gray iron pipe and fittings with this standard coating have provided trouble-free service for decades. Unless otherwise specified, an asphaltic coating is applied to the outside of all pipe and fittings manufactured by AMERICAN.

The asphaltic coating works in conjunction with manufacturing annealing scale to provide a barrier to corrosion. If soils are deemed to be corrosive to ductile iron pipe when evaluated in accordance with the Design Decision Model™ (DDM™*) or Appendix A of AWWA C105, polyethylene wrap or other appropriate methods should be used. If soils are deemed to be corrosive to ductile iron pipe when tested in accordance with Appendix A of AWWA C105, loose polyethylene wrap encasing standard asphaltic-coated pipe as directed by this standard should generally be used. Requests for any other buried corrosion-protection system should be directed to AMERICAN. Asphaltic coating is not compatible with most top coats. See the following alternative primer recommendations.

*DDM™ (Design Decision Model™) developed jointly by Corrpro Companies, Inc., and the Ductile Iron Pipe Research Association. See acipco.com, dipra.org or corrpro.com for details.

MCU UNIVERSAL PRIMER (Moisture-Cured Urethane)

This is a quality, fast-curing, surface-tolerant, immersion-grade, moisture-cured urethane (MCU) specially developed and tested for iron substrates. This coating is essentially a universal primer compatible with all major generic topcoats, including acrylics, epoxies, polyurethanes and moisture-cured urethane topcoats. It can also be topcoated with solvent or water-based asphaltic coatings. For the above reasons, it is well suited for most applications, including where the generic topcoats or end uses may not be known.

Other advantages include a very tough, damage-resistant film resulting in less handling and shipping damage and less touch-up and repair in the field than traditional epoxy primers used in the past. This primer does not have a maximum recoat window and does not require field blast cleaning, as long as the surface is clean and free of dust. This primer is considered a high-performance, chemical-resistant coating suitable for immersion and non-immersion services. Refer to AMERICAN Recommended and Preferred Primer System - Universal Primer (Moisture-cured urethane) for more information and advantages.

PHENOLIC ALKYD PRIMER

This is a fast-drying, lead- and chromate-free, corrosion-resistant primer formulated to accept a wide variety of topcoats. It is well suited for applications where the generic topcoats are unknown but its service is limited to atmospheric exposure. Refer to AMERICAN Alkyd-Phenolic Primer. NOTE: NOT RECOMMENDED FOR IMMERSION. MUST ALLOW UP TO 30 DAYS OF CURING BEFORE TOPCOATING WITH CERTAIN COATINGS.

EPOXY PRIMER

This is a high-solids, chemical- and corrosion-resistant coating for protection against abrasion, moisture, corrosive fumes, chemical attack and immersion.

High-build properties provide outstanding corrosion protection with fewer coats, particularly on edges. Such high-solids, high film-build epoxies are compatible with most catalyzed finish coats.

Typical (field) finish coatings include: epoxies (amine, polyamide, polyamidoamine, water-borne, coal-tar) and polyurethane. Refer to AMERICAN Polyamidoamine Epoxy Primer. NOTE: AFTER 60 DAYS OF CURING, THIS PRIMER SHOULD BE UNIFORMLY SCARIFIED BY BRUSH-BLASTING WITH FINE ABRASIVE BEFORE TOPCOATING.

OTHER SPECIAL COATINGS

AMERICAN can also furnish other special exterior coating systems. Contact AMERICAN for technical assistance in the selection of special exterior coating systems, lead times, and costs.

UNCOATED PIPE

Because some customer applications may require piping or fittings that have no coating applied to the exterior, AMERICAN furnishes, when specified at time of purchase, any of its products without exterior coatings.

NOTE: AMERICAN also has the ability to furnish other primers, but this may affect price and availability.

RECOMMENDED AND PREFERRED PRIMER

MCU Universal Primer
Interior/Exterior/Immersion (Above and Below Grade)

• Single-coat thickness: 3.0-5.0 mils DFT (76-127 microns).
• Typical Topcoats: alkyds, aluminums, epoxies, bituminous, polyurethanes and moisture-cured urethane topcoats.
• Specially developed and tested for iron substrates.
• Single component.
• Low-temperature, fast-curing capability.
• Can be applied over damp, but not wet surfaces.
• Infinite recoat window, as long as surface is clean and free of dust before topcoating.
• This primer is compliant with ANSI/NSF Standard 61 as a primer and spigot surface coating for pipe, fittings, and valves when combined with approved topcoats.

OTHER PRIMERS

Alkyd-Phenolic Primer
Interior/Exterior/Non-Immersion (Above Grade Only)

• Single-coat thickness: 2.0-4.0 mils DFT (50-101 microns).
• Typical Topcoats: alkyds, aluminums, epoxies, and urethanes.
• Coating must be cured for 30 days before being overcoated with certain topcoats.
• This primer is not recommended for immersion service.
• This primer is compliant with NSF Standard 61 as an exterior surface coating only.

Polyamidoamine Epoxy Primer
Interior/Exterior/Immersion (Above and Below Grade)

• Single-coat thickness: 3.0-8.0 mils DFT (76-203 microns).
• Typical Topcoats: epoxies and urethanes.
• This coating must be lightly blast cleaned before topcoating if it has not been exterior exposed for 60 days or longer.
• This primer is compliant with ANSI/NSF Standard 61 for potable water contact for pipe, fittings, and valves when combined with approved topcoats.

In areas where severely aggressive soils are encountered, the use of a polyethylene tube or sheet encasement has been proven to provide highly effective, economical protection. The protection against corrosion provided by loose polyethylene is different in several ways and should not be confused with coatings applied directly to the barrel of the pipe. The most significant difference is its ability to protect without creation of concentration cells at holidays. Also, since the encasement is applied when the pipe is actually put in the ground, coating damage due to shipping, handling, etc., is minimized.

As water may be present in the soil around the pipe, water may also be present between the pipe and wrap. Water inside the polyethylene tubing initially bears some characteristics of the soil environment, and corrosion may start. But within a short period of time initial oxidation depletes the oxygen supply in the water, and other electrochemical corrosion reactions also progress to completion. At this point a state of chemical equilibrium is reached.

Since the first field installation of polyethylene wrap on gray iron pipe in 1958, installations have been made in severely corrosive soils throughout the United States. The success of the polyethylene encasement procedure developed in the United States has been adopted by several other countries, and an International Standard for Polyethylene Sleeving (ISO-8180) has been developed.

Research by the Ductile Iron Pipe Research Association at several severely corrosive test sites has verified that polyethylene encasement provides a high degree of protection and results in minimal and generally insignificant exterior surface corrosion of either ductile or gray iron pipe thus protected. These findings have been confirmed by the results of numerous investigations of field installations.

Field tests have also indicated that the dielectric capability of polyethylene provides shielding for ductile and gray iron pipe against stray current at most levels encountered in the field.

Because polyethylene encasement is a passive method of protecting ductile iron pipe in aggressive soils, it can effect greater reliability and savings than cathodic protection systems which require continual monitoring, maintenance and other operating expenses, and trained personnel. Cathodic protection systems can also cause collateral harm in some cases to nearby unprotected ferrous structures.

For protection in areas of severely aggressive soils, AWWA C105 covers materials and installation procedures for polyethylene encasement of underground installations of ductile iron piping for water and other liquids.

Polyethylene wrap in tube or sheet form for piping encasement is manufactured of virgin polyethylene material conforming to the requirements of ANSI/ASTM Standard Specification D1248. The specified minimum thickness for linear low-density polyethylene film is 0.008 in. (8 mils). The specified minimum thickness for high-density, cross-laminated polyethylene film is 0.004 in. (4 mils).

Material, required markings, and installation methods are all in accordance with the requirements of AWWA C105. This standard and more detailed publications by DIPRA regarding loose polyethylene encasement are available from AMERICAN.

ADIP Table No. 11-2

Notes:
*Based on one turn at each end, six 4"-long strips to secure loose wrap plus approximately 5% extra.
+Flat tube widths are shown for Fastite, Flex-Ring, Lok-Ring, and MJ Joints. Check AMERICAN for Flat tube widths required for Flex-Lok Joints.
The standard color for low-density polyethylene is black. It can also be furnished white, green, red, buff, royal blue and lavender on special order. The standard color for high-density, cross-laminated polyethylene is white. It can also be furnished black on special order.

Installment methods as set forth in ANSI/AWWA C105/A21.5 and DIPRA's "Polyethelyne Encasement" brochure should be followed.