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 by NSF International in accordance with NSF/ANSI/CAN Std. 61 and the extraction requirements of NSF/ANSI/CAN 600. Reference Tnemec’s certified product listing at for additional details.

Meets zinc-rich primer requirements of the latest edition of AWWA D102 Standard for Inside System No. 3, 5, and 6 and Outside System No. 3, 4, and 6. Series 91-H2O uses a zinc pigment that meets the requirements of ASTM D 520 Type III and contains less than 0.002% 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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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 ½ hours||5 hours|
|55°F (11°C)||2 hours||6 hours|
|45°F (7°C)||2 ½ 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 D102. 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.


Interior: Series 21, 22, FC22, L140, L140F, N140, N140F, 406.
Exterior: Series 27, 66, L69, L69F, N69, N69F, 73, 115, V115, L140, L140F, N140, N140F, 161, 1026, 1028, 1029, 1094, 1095, 1096. Note: Certain topcoat colors may not provide one-coat hiding depending on the 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.

Volume Solids

63.0 ± 2.0% (mixed)

Recommended DFT

2.5 to 3.5 mils (65 to 90 microns). Note: Reference the NSF website at for details on the maximum allowable DFT.

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)


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)

Theoretical Coverage

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

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