Series 91-H2O


Generic Type

Aromatic Urethane, Zinc-Rich

Common Usage

A two-component, moisture-cured, zinc-rich primer for the interior and exterior of steel potable water tanks. Provides outstanding long-term corrosion resistance when used as a primer in conjunction with other Tnemec potable water tank coatings. It cures quickly and can be topcoated the same day at surface temperatures down to 35°F (2°C). Series 91-H2O has no maximum recoat time, making it ideally suited as a primer for both sides of plate steel surfaces in water tank fabrication shops. Application methods include “dry-fall” under certain conditions (see Application). Note: When used in conjunction with cathodic protection, anodes or impressed current systems should not provide current demand more negative than –1.05 volts relative to a copper–copper sulfate reference electrode half-cell.

Special Qualifications

Certified (with or without 44-710 Urethane Accelerator) by NSF International in accordance with NSF/ANSI/CAN Std. 61 and the extraction requirements of NSF/ANSI/CAN 600 and is qualified for use on interior potable water tanks of 1,500 gallons (5,678 L) capacity or greater, pipes 24 inches (61 cm) in diameter or greater, valves 3/4 inch (3.8 cm) in diameter or greater, fittings ½ inch (1.3 cm) in diameter or greater, and pumps 3/4 inches (1.9 cm) in diameter or greater. Topcoating with Std. 61 certified Tnemec coatings is required. Contact your Tnemec representative for specific recommendations. Reference Tnemec's certified product listing at for details on the maximum allowable DFT. Meets zinc-rich primer requirements of AWWA D102-17 Standard for Inside System No. 3 & 5 and Outside System No. 3, 4 & 6. Series 91-H2O uses a zinc pigment which meets the requirements of ASTM D 520 Type III and contains less than .002% lead.

This product is part of a coating system tested in accordance with ISO 12944-6 (2018). Contact your Tnemec representative for coating system test results.

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  • Greenish-Gray

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Interior: Series 20, FC20, 22, FC22, L140, L140F, N140, N140F, V140, V140F, 141, 406.
Exterior: Series 27, 27WB, 66, L69, L69F, N69, N69F, 73, 115, L140, L140F, N140, N140F, V140, V140F, 161, 1026, 1028, 1029, 1074, 1074U, 1075, 1075U, 1094, 1095, 1096. Note: Certain topcoat colors may not provide one-coat hiding depending on method of application. Contact your Tnemec representative. Note: Series 91-H2O must be exterior exposed for three days prior to topcoating with Series 1028 or 1029. Note: Series 91-H2O must be exterior exposed for one day prior to topcoating with Series 27WB.

Number of Components

Two: Part A and Part B

Curing Time

Without 44-710

|Temperature †||To Handle||To Recoat|
|75°F (24°C)||1 hour||4 hours|
|65°F (18°C)||1 1/2 hours||5 hours|
|55°F (11°C)||2 hours||6 hours|
|45°F (7°C)||2 1/2 hours||7 hours|
|35°F (2°C)||3 hours||8 hours|
---† 50% relative humidity. Note: Refer to product listings on for specific potable water return to service information. Curing time will vary with surface temperature, humidity and film thickness. Ventilation: When used as a tank lining or in enclosed areas, provide adequate ventilation during application and cure. Reference ventilation guidelines contained in the latest edition of AWWA D 102.
Note: For faster curing, low humidity and low-temperature applications, add No. 44-710 Urethane Accelerator (see separate product data sheet). Note: For cure times to immersion service, reference the specified Tnemec interior topcoat product data sheet.

Volume Solids

63.0 ± 2.0% (mixed)

Volatile Organic Compounds

Unthinned: 2.65 lbs/gallon (318 grams/litre)
Thinned 2.5%: 2.76 lbs/gallon (331 grams/litre)
Thinned 10%: 3.07 lbs/gallon (368 grams/litre)

Recommended DFT

2.5 to 3.5 mils (65 to 90 microns)

Theoretical Coverage

1,011 mil sq ft/gal (24.8 m²/L at 25 microns). See APPLICATION for coverage rates.


Unthinned: 5.05 lbs/gal solids
Thinned 2.5%: 5.33 lbs/gal solids (No. 2 Thinner); 5.06 lbs/gal solids (No. 3 Thinner)
Thinned 10%: 6.19 lbs/gal solids (No. 2 Thinner); 5.09 lbs/gal solids (No. 3 Thinner)

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