Pettit SR-21 Hard Antifouling Paint dries in 15 minutes and is a great bottom paint choice for boats used in fresh water.
Pettit Z-Spar Pettit Z-Spar
  • Pettit SR-21 Hard Antifouling Paint dries in 15 minutes and is a great bottom paint choice for boats used in fresh water.

Pettit SR-21 Fresh Water Hard Antifouling Paint

Pettit SR-21 Fresh Water Hard Antifouling Paint infuses slicking agents into an ultra-thin low friction film to create the ideal racing finish. Dual biocides of both copper and Irgarol prevent the attachment of fouling organisms. This slick, fast-drying coating is easy to apply and lets you launch in as little as 15 minutes at 70°F.

SR-21 is recommended for use on fiberglass, wood, properly primed steel boats, and previously painted surfaces.

SR-21 is available in Blue and Bronze colors.
$71.45 / qt
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Tech Spec Product Info User Generated Content
Note: The chemical compound behind the highly effective anti-slime additive Irgarol was unavailable for several years. Paint manufacturers substituted additional zinc in its absence to ensure similar antifouling performance. Bottom paints containing Irgarol are once again available, and are recommended for extra protection in medium to severe fouling conditions. SR-21 Blue and Bronze paints contain Irgarol.

SR-21 Features

  • Easy to apply.
  • Launch in 15 minutes.
  • Super-slick finish contains moly-disulfide and PTFE for increased speed.
  • Ultra-thin film technology prevents paint buildup.
  • Eliminates sanding between coats.
  • Dual biocide controls hard and soft fouling.
  • 100% compatible with Interlux VC-17


Mix all of the copper powder into the liquid portion stirring thoroughly to ensure the copper powder is evenly dispersed in the liquid. Stir occasionally during application. Apply SR-21 with a short nap (no more than 3/16 inch nap) or foam roller. Roll quickly in one direction only using a fairly dry roller to minimize lap marks. For spray application use an airless spray gun with a .011 to .015 inch tip. Apply a wet coat of product by holding the gun no more than 10 inches from the hull. Do not use conventional spray equipment to apply this product. Apply at three mils wet to achieve a dry film thickness of 0.25 mils per coat. Adhere to all application instructions, precautions, conditions and limitations to obtain optimum performance. Refer to individual labels and tech sheets for detailed instructions when using associated products, etc. Do no thin SR-21 more than 10% (2.5 ounces per quart kit) or inadequate paint film thickness will occur and premature erosion of the finish will be likely.


All surfaces must be clean, dry and properly prepared prior to painting. Coating performance, in general, is proportional to the degree of surface preparation. Follow recommendations carefully, avoiding shortcuts. Inadequate preparation of surfaces will virtually assure inadequate coating performance.


No antifouling paint can be effective under all conditions of exposure. Man made pollution and natural occurrences can adversely affect antifouling paint performance. Extreme hot and cold water temperatures, silt, dirt, oil, brackish water and even electrolysis can ruin an antifouling paint. Therefore, we strongly suggest that the bottom of the boat be checked regularly to make sure it is clean and that no growth is occurring. Lightly scrub the bottom with a soft brush to remove anything from the antifouling paint surface. Scrubbing is particularly important with boats that are idle for extended periods of time. The coating is most effective when the boat is used periodically.


Previously Painted Surfaces: If the previous coating is in good condition, thoroughly sand with 80 grit paper followed by thorough sanding with 180-grit then 220-grit and finally 320-grit sandpaper to achieve a smooth nonporous surface. Then solvent clean with Pettit 120 Brushing Thinner to remove residue. Apply three coats of SR-21. If the previous coating is soft or in poor condition, remove to the bare surface by sanding or using Pettit 9050 Bottom Paint Remover. Proceed with the appropriate bare system as described below. Old tin copolymers should be removed before applying SR-21 Antifouling Paint.

Bare Fiberglass: All bare fiberglass, regardless of age, must be thoroughly cleaned several times with Pettit 95 Fiberglass Dewaxer. Sand thoroughly with 320-grit sandpaper to a dull, frosty finish and rewash the sanded surface with 95 Fiberglass Dewaxer to remove sanding residue. Then apply three coats of SR-21, following application instructions. Careful observation of the above instructions will help ensure long term adhesion of this and subsequent years' antifouling paint. To eliminate the sanding operation, wash the fiberglass three times using Pettit 95 Fiberglass Dewaxer. Then apply one thin continuous coat of Pettit 6999 Sandless Primer. Topcoat with three costs of SR-21 carefully following the topcoating instructions on the Sandless Primer label. (Use the set-to-touch recoat time over the 6999 Sandless Primer. Do not apply SR-21 over 6999 Sandless Primer that has dried beyond the tack-free state).

Bare Wood: Sand entire surface with 80 grit paper; wash clean with Pettit 120 Brushing Thinner. Apply three coats of SR-21 Antifouling Paint.

Bare Steel: Sandblast or disc sand to a clean, bright finish and remove residue. Then immediately apply two coats of 6980 Rustlok Steel Primer, allowing each to dry only 1-2 hours prior to overcoating. Follow with two coats of Pettit Protect 4700/4701 High Build Epoxy Primer allowing each to dry from two to 24 hours depending upon temperature. Apply three finish coats of SR-21 Antifouling Paint.

Keels - Lead: Abrade surface to bright metal and clean off residue. Apply one thin coat of 6455/044 Metal Primer; allow to dry two hours. Apply one coat of Pettit 6627 Tie Coat Primer then, if fairing is required, apply 7000/7001 Epoxy Fairing Compound. Follow with an additional coat of 6627 Tie Coat Primer per label directions. Apply three finish coats of SR-21 Antifouling Paint.

Keels - Steel or Cast Iron: Abrade surface to bright metal and clean off residue. Apply one coat of 6980 Rustlok Steel Primer, allowing to dry only 1 - 2 hours prior to overcoating. Then, if fairing is required, apply 7000/7001 Epoxy Fairing Compound followed by two coats of Pettit 6627 Tie Coat Primer, finish with three finish coats of SR-21 Antifouling Paint.


Minimum DRY TIME at Substrate Temperature  To Recoat  To Launch 
90 Degrees F  10 minutes  10 minutes 
70 Degrees F   10 minutes  15 minutes 
40 Degrees F  30 minutes  30 minutes 



  • FINISH.....Metallic - Flat
  • COLORS.....1221 Blue, 1921 Bronze
  • SOLIDS (theoretical) : By weight.....31+- 2%
  • COVERAGE.....90 sq. ft/quart kit
  • VOC....740 g/l (6.18 lbs/gal) max
  • FLASH POINT....68 degrees F
  • ACTIVE INGREDIENTS...Copper Flake...21.0%
  • ACTIVE INGREDIENTS...Irgarol...2.0%

  • METHOD.....Short Nap Roller or Airless Spray; maximum roller thickness - 3/16"
  • NUMBER OF COATS....Three initial; one or two in subsequent years
  • APPLICATION TEMP.....40 degrees F. Minimum, 90 degrees F. Maximum
  • THINNER......Isopropyl Alcohol


BRAND: Pettit Z-Spar
Number Of Parts: One Part
Type: Racing Bottom Paint
5.0 1

I was able to get this shipped promptly.


Arrived timely and good condition.




Pettit SR-21 Fresh Water Hard Antifouling Paint



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