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Polyurethane
Coating Specifications for
Ductile Iron Pipe and Fittings
MATERIAL: The
coating/lining material shall consist of an ASTM D16 Type V, 100% solids polyisocyanate
resin and polyol resin as manufactured by Madison Chemical Industries, Inc. or equivalent
that meets the following requirements:
| MATERIAL PROPERTIES |
REQUIREMENT |
| % Solids (ASTM D-1259-A) |
98% ± 2% |
| Volatile Organic Compounds
(VOCs) |
<2% or 12 grams/litre |
| % coal tar content |
0% |
| Dry-to-touch time |
<20 minutes @ 70° F(20° C) |
| Mix Ratio |
1:1 |
| # of Coats to Achieve
Recommended Dry Film Thickness |
1 coat (multi-pass) |
| Application Temperature Range |
-40° F(-40° C) to 150° F(65° C) |
| Cure Time to Immersion Service |
48 hours @ 70° F(20° C) |
| PERFORMANCE PROPERTIES |
REQUIREMENT |
| Tensile Adhesion (ASTM D-4541)
to ductile iron |
>2000 psi |
| Cathodic Disbondment ASTM G-8
(28 day/20C/40 mils, on ductile iron) |
<15 mm radius |
| Impact Resistance ASTM D-2794
(5/8” ball, 40 mils) |
>100 in-lbs. |
| Flexibility (ASTM D-522) 18
mils over 1" mandrill |
>180° |
| Hardness (ASTM D-2240) |
Shore D 65 ± 5 |
| Abrasion Resistance (ASTM
D-4060) CS17, 1 kg wheel |
<100 mg loss per 1000 rev. |
| Chemical Resistance (ASTM
D-543) 10% H2SO4, 10% Hcl, 30% NaOH, H2S, Raw Sewage |
<5% weight change 90 days |
| Health Approval (for potable
water interiors only) |
NSF 61 |
| Material History of Successful
Application & Performance (for specific application) |
>5 years |
SURFACE
PREPARATION: All surfaces to be coated or lined should be cleaned to a near white metal
finish as described in SSPC-SP10 as it applies to ductile iron pipe. All surfaces to be
coated shall be completely dry, free of moisture, dust, grease or any other deleterious
substances at the time the coating or lining is applied.
THICKNESS: The required thickness
is as follows for the respective applications:
| APPLICATION |
FILM THICKNESS |
| Internal Wastewater/ Potable
Water |
40 mils (1000 microns) nominal/
35 mils (875 microns) minimum |
| External |
25 mils (625 microns) nominal/
20 mils (500 microns) minimum |
| Valves, fittings (external) |
25 mils (625 microns) nominal/
20 mils (500 microns) minimum |
| Slip Bore/ Rock Shield
(external) - moderate |
40 mils (1000 microns) nominal/
35 mils (875 microns) minimum |
| Other internal |
see Madison Chemical |
COATING
APPLICATION: A heated, plural component airless spray pump (1:1 ratio) is to be used to
apply the coating in one coat, multi-pass operation. No primers are to be used.
INSPECTION:
A) Holiday inspection shall be
conducted as per NACE RP0188 using either a wet sponge or a spark tester. The spark tester
voltage is to be 50 volts per mil of thickness (2 volts per micron). The testing may be
conducted any time after the coating has reached sufficient cure. Repairs are to be made
as per coating manufacturer’s recommendations.
B) Visual: The finished coating
shall be generally smooth and free of sharp protrusions. A minor amount of sags, dimpling
and curtaining which does not exceed 5% of the surface shall not be considered cause for
rejection.
WARRANTY: A two year written or
published performance warranty must be provided. |
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