How to apply Pettit SR-21 Antifouling paint

This information provided here has been reproduced courtesy of Pettit Paint Company. Wholesale Marine reproduced this information on 3/11/2010.

SR-21 Antifouling Paint forms an ultra-thin low friction fi lm for boat bottoms. It is the ideal racing fi nish for fresh water or cold saltwater boats. SR-21 contains copper powder as well as a slime reducing biocide to prevent the attachment of fouling organisms such as barnacles, bryozoa, toredos, zebra mussels and algae. SR-21 contains two slicking agents PTFE (polytetrafl uoroethylene) and Molybdenum Disulfi de which reduce surface friction allowing the hull to slide through the water. SR-21 is recommended for use on fi berglass, wood and properly primed steel boats.

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 fi lm 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 fi lm thickness will occur and premature erosion of the fi nish 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.

FINISH…..Metallic – Flat
COLORS…..1221 Blue, 1921 Bronze
SOLIDS (theoretical)
By weight…..31 plus or minus 2%
By volume……8 plus or minus 2%
COVERAGE…..90 sq. ft/quart kit
VOC….740 g/l (6.18 lbs/gal) max
FLASH POINT….68 degrees F
Copper Flake…………………21.0%
N-Cyclopropyl-N (1,1 -dimethylethyl)
-6-(methylthio) -1,3,5- triazine-2
METHOD…..Short Nap Roller or Airless Spray
NUMBER OF COATS….Three initial; one or
two in subsequent years
APPLICATION TEMP…..40 degrees F. Min. / 90 degrees F. Max.
DRY TIME* (minutes)
To Recoat To Launch
90 degrees F 5 30
70 degrees F 10 60
40 degrees F 20 120
*The above dry times are minimums. SR-21 may be recoated and launched after the minimum time shown.
THINNERS…..Isopropyl Alcohol
95 Fiberglass Dewaxer
6999 Sandless Primer

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 fi nally 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 9051 Bio Blast 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 fi berglass, regardless of age, must be thoroughly cleaned several times with Pettit 95 Fiberglass Dewaxer. Sand thoroughly with 320-grit sandpaper to a dull, frosty fi nish 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 antifouling paint subsequent years. To eliminate the sanding operation, wash the fi berglass 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 fi nish 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 fi nish 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 Epoxy Fairing Compound. Follow with an additional coat of 6627 Tie Coat Primer per label directions. Apply three fi nish 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 Epoxy Fairing Compound followed by two coats of Pettit 6627 Tie Coat Primer, fi nish with three fi nish coats of SR-21 Antifouling Paint. DO NOT APPLY SR-21 ON ALUMINUM HULLS OR OUTDRIVES

*This is a simplied system for smaller areas designed for good performance and easy application by the boatyard professional or do-it-yourselfer. For larger vessels or for application where a high performance, professional system is desired, please refer to Technical Bulletin 431, Pettit Protect 4700/4701 High Build Epoxy Primer or consult your local Pettit representative or the Pettit Technical Department.

Share and Enjoy:
  • Print
  • Digg
  • StumbleUpon
  • Facebook
  • Yahoo! Buzz
  • Twitter
  • Google Bookmarks

Leave a Reply

You must be logged in to post a comment.