Site Switcher
Select country usa United States
AkzoNobel
Paint Guides

How to fully paint bare GRP / FRP

Paint Guide BW057

  • I am going to work on a surface below the waterline change
  • I want to do a full paint or repaint change
  • I am going to paint my hull / keel change
  • The part I want to paint is Fiberglass change
  • The surface is bare change

Paint job at a glance

Print this guide

Here's your custom paint guide

  • Step 1 Cleaning bare GRP / FRP

    1.1

    paintguide.detail.step.mediatitle

    https://www.youtube.com/embed/BUAhhD7wilE

    1.1 Rinse

    • Rinse the surface with fresh water to remove loose dirt, growth or any other contamination. You can also scrub it with a hard sponge.

    • Show tips from pros

      • All mold release agents, waxes or polishes must be removed prior to sanding the surface so it’s important to ensure the surface is properly degreased.
      • To tell if the surface is properly degreased, the water should spread across the surface while flushing. Small droplets of water are an indicator that the surface isn’t fully degreased. If so, repeat the cleaning process.
      • When degreasing with solvent, work with the 2-cloth method: use one cloth soaked with solvent and then wipe straight after with a clean cloth to remove the contamination.
      • Use a slow evaporating solvent to have enough time to wipe the surface with the clean cloth.
      • Change the cloths regularly to avoid spreading the dirt back to the surface.

    • Show equipment you'll need

      • Bucket
      • High pressure washer
      • Extension for cleaning tool
      • Sponge and/or cloths
      • Rubber gloves
      • Safety shoes
      • Overalls
      • Eye protection
      • Specialized cleaning product

  • Step 2 Sanding bare GRP / FRP

    2.1 2.2 2.3

    paintguide.detail.step.mediatitle

    https://www.youtube.com/embed/oKFhU7YVJi8

    2.1 Sanding

    • Sand using 60-120 grit to achieve a rough surface profile to improve adhesion.

    2.2 Clean surface

    • Remove any sanding residues with clean compressed air, sweep the surface with a clean brush, or vacuum clean for the best results.
    • The final particles can be removed by wiping off the surface with a suitable solvent.

    2.3 Fill any pinholes

    • If any pinholes or air inclusions appear, they will need filling before you continue.

    • Show tips from pros

      • Sanding too hard may reveal porosity deep in the gel coat that can then be very hard to fill.
      • For large and flat areas, we recommend you use a sanding machine in combination with a vacuum cleaner. For radius and edges just sand by hand. And remember, the sandpaper should be tightly fitted around an interface pad or soft foam.

    • Show equipment you'll need

      • Sanding paper 60 - 120 grit (various grades for surface preparation)
      • Vacuum cleaner (or compressed air)
      • Cleaning thinner
      • Rubber gloves
      • Dust mask
      • Tack rag or lint free cloth
      • Overalls
      • Sanding machine and/or suitable sanding blocks
      • Eye protection

  • Step 3 Applying fillers and epoxies

    3.1 3.2 3.3 3.4

    paintguide.detail.step.mediatitle

    https://www.youtube.com/embed/9MSiZh3sQDs

    If you’re doing repair work, carefully inspect for any damage including fine cracks and any material that’s poorly adhered. Small repairs and filling on new boats can be easily tackled. However, any work that’s over a larger area or might affect the structure or hull integrity, should be referred to a professional for proper assessment.

    It's recommended to apply a layer of primer before application of filler. Please see step relating to the application of primer.

    Important note relating to filling and fairing: If you are intending to carry out any filling and/or fairing work please read the following note very carefully.
    On all bare substrates a coat of primer MUST be applied before proceeding with any filling and/or fairing. Once this work has been completed then the second and subsequent coats of primer should be applied before proceeding with application of the rest of the chosen above or below waterline system.

    3.1 Mask off

    • Mask off any areas that are not going to be painted such as topsides on the waterline with suitable masking tape.

    3.2 Mixing

    • Most fillers used in the marine environment are two pack epoxy based fillers. For more specific information, please refer to the datasheet or the label on the can.
    • Two pack products:
      • Measure out part A and part B onto a clean mixing board using the specified mix ratio.
      • Using a palette knife or spatula, mix the two components together until you achieve a uniform colour with no streaks.
    • To maximise the working time of the product, spread it out over the mixing board to prevent it curing too quickly.

    3.3 Application

    • The best way is to apply filler using a palette knife, spatula or any other suitable tools in smooth, thin layers. Try not to apply too much in one go. You may need to apply multiple layers.
    • Allow it to cure following the instructions on the datasheets or label. Two pack products have a limited pot life when mixed. Refer to label or technical data sheet for further information.

    3.4 Sanding and overcoating

    • After the filler has been applied and has cured, you need to smooth the surface using a sanding block that will ideally be larger than the filled area. The larger the filled area, the larger the block will need to be to sand it.
    • Initial sanding can be completed with 80 grit. If additional filler needs to be applied, remove the dust from the surface and follow the previous step. Once the surface is smooth and no more filler is needed, final sanding can be completed with 120-180 grit.

    • Show tips from pros

      • Epoxies must be mixed in the proper ratio. Add too much curing agent and they will leave a sticky film on the surface that’s not suitable for overcoating. Too little curing agent will weaken the filler and cause it to crumble later on.
      • When measuring out epoxy filler that has to be mixed 2:1 by volume, the easiest way is to measure out three equal volume piles (2 of the base and 1 of the curing agent/hardener) rather than trying to gauge if one is twice the other.
      • Metal measuring spoons of various sizes that you can buy from the supermarket, are ideal for measuring small quantities of product.
      • Below the waterline, epoxy fillers must be used. Polyester or car fillers should not be used as they have a greater tendency to absorb water.
      • Never add thinners to fillers as this will seriously affect the integrity of the cured product.
      • Old plastic credit cards make excellent application and smoothing tools for smaller areas of filler.
      • When sanding fillers, it’s very easy to inadvertently sand surrounding areas forming a lower area that will show right through to the finish. Be careful to avoid this.

    • Show equipment you'll need

      • Sanding paper 80 - 180 grit (various grades for surface preparation)
      • Palette knife, spreader or small trowel
      • Safety shoes
      • Face dust masks
      • Hand protection (as per product SDS)
      • Overalls
      • Sanding machine and/or suitable sanding blocks
      • Eye protection

  • Step 4 Applying underwater primers

    4.1 4.2 4.3 4.4

    paintguide.detail.step.mediatitle

    https://www.youtube.com/embed/9x-VwjBzB5U

    Priming is a vital part of the painting process as it’s the base on which the rest of the system will be applied. If the base isn’t good and sound, then the overall system won’t be either.

    Important note relating to filling and fairing: If you are intending to carry out any filling and/or fairing work please read the following note very carefully.
    On all bare substrates a coat of primer MUST be applied before proceeding with any filling and/or fairing. Once this work has been completed then the second and subsequent coats of primer should be applied before proceeding with application of the rest of the chosen above or below waterline system.

    4.1 Mask off

    • Mask off any areas that are not going to be painted such as topsides on the waterline with suitable masking tape.

    4.2 Mixing

    • Single pack products:


      • With single pack primer mix the paint thoroughly with a stirring stick ensuring that any settlement is well mixed in.
    • Two pack products:


      • If you are using a 2 pack primer, mix the individual components thoroughly. Two pack products have a limited pot life when mixed. Refer to label or technical data sheet for further information.
      • Combine the two products and mix the paint thoroughly as indicated on the datasheet or the label on the can.
    • In some instances, it's necessary in to add solvents such as to aid application or improve penetration of the first coat on wood. For the recommended solvent and the amount you need to add, please refer to the datasheet or the label on the can.

    4.3 Application

    • Pour the paint into a clean roller tray or paint pot.
    • Start somewhere where any application overlap will be less noticeable such as on the bow or the corner of the transom.
    • For large surfaces, it's advised to use a roller as it's quicker and will achieve a uniform finish.
    • If you’re applying product with a brush, a good technique is the criss-cross method. Paint is applied to the surface with diagonal brushing from left to right. It’s then spread further with horizontal strokes before finally laying off with light vertical strokes. This applies a uniform layer of paint and allows the brush marks to flow out better.
    • Apply sufficient paint for the product to flow, but not so much to make it sag or run as it can be hard to remove them later. If you do see any sags or runs, brush them out as soon as possible.

    4.4 Overcoating

    • Most products will require more than one application or coat as per datasheet or label on the can.
    • If any filling is required this should be done after the first coat of primer is applied.
    • If additional coats are required, follow the recommended overcoating times as per the datasheet or label on the can.
    • Most primers have extended recoat times with themselves, so you can apply the required number of coats without having to sand in-between. If you exceed the maximum overcoating time, you will need to sand the surface with 120-180 before applying the next coat. When applying antifouling over primers some have limited recoat times so check labels and technical data sheets for any primer used to ensure you are within the recoat window for the antifouling product being applied.
    • Product performance is based upon the film thickness, so please make sure the recommended number of coats are applied.

    • Show tips from pros

      Working with a roller:

      • Applying paint with a roller is a fast method of covering large areas.
      • For most applications, a 3/8th nap felt or mohair roller is suitable. Before using them, wrap masking tape around a new roller and then pull off to remove any loose fibres.
      • If you're trying to achieve a smoother finish, you could use a high density closed cell foam roller. This may lead to a thinner coat of product, so you may need to apply an extra coat.
      • Some rollers may be affected by solvents in the product and can swell during use. When they become too soft to use, or look like they are breaking up, replace them with a new one.
      • When using a roller and tray, it’s a good idea to keep the tray covered loosely to avoid the wind, sun or air creating a skin over the paint during use.
      • If the area to be painted is very small you can obtain smaller rollers from various hardware stores. Some are often called radiator rollers that are very good for small and difficult to get to areas.

      Working with a brush:

      • Brushes should be medium to large width typically 2-4 inches with long flexible bristles.
      • A smaller brush will be used for painting difficult to reach areas.
      • Wash your brushes with the appropriate solvent and dry them thoroughly before using to avoid contamination.
      • The quality of brushes required for priming is less critical than those used for applying undercoats or finish coats.
      • To minimise brush marks hold the brush at a 45 degree angle to the surface.
      • To clean brushes, place some thinner inside a suitable container so you can clean it if the bristles start to clog due to curing or thickening of the paint.

      Other useful tips:

      • If you’re getting runs as the paint is applied, then it’s either too thin, or you’re applying too much.
      • Avoid using paint directly from the can as this might introduce contamination and prematurely age the paint from solvent evaporation. Instead, pour what you’d expect to use in 30 minutes into a separate container.
      • Old jam jars or clean dry tin cans are useful for mixing paint. Also, metal measuring spoons of various sizes you can buy from any supermarket, are ideal for measuring small quantities of paint and hardener for the smaller jobs.
      • For primers that you’re applying with antifouling, you need to ensure that the interval time between the end of the application of the epoxy primer and the first coat of antifouling is no longer than stated on the datasheet or label. This is especially true with epoxy based primers. If you miss this interval, you’ll have to either sand the primer or apply another coat and ensure you don’t miss the overcoat interval the second time around.
      • If any of the applied coats develops runs or sags (or has contamination in it) that you need to sand out, use 120-220 grit paper. Start with 220 grade and if it keeps clogging change to 120. Any coarser and you run the risk of removing too much product and/or sanding through to the substrate. Refer to label data for self-on-self recoating information, plus antifoulings over coating times.

    • Show equipment you'll need

      • Sanding paper 120 - 220 grit (various grades for surface preparation)
      • Paint roller tray
      • Paint rollers (suitable sizes and types)
      • Paint brushes (suitable sizes)
      • Tack rag or lint free cloth
      • Safety shoes
      • Face dust masks
      • Hand protection (as per product SDS)
      • Overalls
      • Sanding machine and/or suitable sanding blocks
      • Eye protection

  • Step 5 Applying antifouling paint

    5.1 5.2 5.3 5.4 5.5

    paintguide.detail.step.mediatitle

    https://www.youtube.com/embed/3W0ABkUrqIc

    5.1 Mask off

    • Mask off any areas that are not going to be painted such as topsides on the waterline with suitable masking tape.

    5.2 Mixing

    • Single pack products:


      • With single pack antifoulings mix the paint thoroughly with a stirring stick ensuring that any settlement is well mixed in. Stir frequently during application as the heavy compounds may settle during use.
    • Two pack products:


      • If you are using a 2 pack antifouling, mix the individual components thoroughly (if both are liquid). For some products the second component can be a powder.
      • Combine the two components and mix the paint thoroughly as indicated on the datasheet or the can.

    5.3 Application

    • Antifouling paints are formulated to be applied as they are, so there’s no need to add thinners to them. However, there are some occasions where a small amount of solvent can be added to aid application. Diluting the antifouling too much will affect the amount of product that's applied to the surface and in turn its long term performance. Please see tips for more details.
    • Pour the paint into a clean roller tray.
    • Roll or brush the paint onto the surface ensuring that a good even film of paint is applied. For additional information related to your specific product, please refer to the datasheet, the label on the can or further information on this website.
    • Allow the paint to dry as per datasheet or label on the can.

    5.4 Overcoating

    • Most products will require more than one application or coat as per datasheet or label on the can.
    • If additional coats are required follow the recommended overcoating times as per the datasheet or label on the can.
    • It is good practise to apply an extra coat to leading and trailing edges such as the waterline, trim tabs, outdrives, keels and rudders. These areas experience more water flow and turbulence and hence more wear on the paint surface.

    5.5 Finishing up

    • Be sure to follow immersion times carefully. If you don’t, it could result in the detachment, blistering or cracking of the antifouling. The marine environment is harsh so the paint must be allowed to dry thoroughly before immersion.
    • Once the paint is dry, remove all masking tape.
    • To clean equipment, use the recommended solvent from the datasheet or the label on the can.
    • For waste disposal please refer to the top of this guide.

    • Show tips from pros

      Working with a roller:

      • Applying paint with a roller is a fast method of covering large areas.
      • For most antifoulings applications a 3/8th nap solvent resistant mohair roller is suitable. For thinner antifoulings, a 1/8th inch nap solvent resistant mohair roller, or a high density closed cell foam roller should be used.
      • If rollering with felt or mohair rollers, wrap masking tape around a new roller and then pull off to remove any loose fibres.
      • Some rollers may be affected by solvents in the product and can swell during use. When they become too soft to use, or look like they are breaking up, replace them with a new one.
      • When using a roller and tray it is a good idea to keep the tray covered loosely to avoid the wind, sun or air creating a skin over the paint during use.

      Working with a brush:

      • Brushes are best used for small areas. As the finish achieved is unlikely to be as good as a topside finish, the type of brush you use isn’t so critical.
      • Wash your brushes with the thinner and dry them thoroughly before use to avoid contamination.

      Other useful tips:

      • If it is particularly hot or cold weather conditions, you can add a small amount of suitable thinner (no more than 10%) to help ease the application. Check labels and data sheets to ensure that the correct thinners are used as some antifouling products are water based.
      • Never add anything else (additives, etc.) to an antifouling as this won’t improve performance of your coating. It may adversely affect the chemistry of the paint formulation. In many regions or countries it is also illegal to do this.
      • Do not mix different antifoulings because they could be based on a different chemistry and may impact performance.
      • Don't leave masking tape on longer than needed as it will be difficult to remove.
      • Ensure you apply the correct amount of paint as stated in the datasheet.

    • Show equipment you'll need

      • Solvent mask
      • Paint rollers (suitable sizes and types)
      • Paint brushes (suitable sizes)
      • Safety shoes
      • Hand protection (as per product SDS)
      • Overalls
      • Eye protection

We're here to help

We're ready to help. Our friendly helpdesk is open weekdays 8:00 - 16:30
Call 1-800-468-7589
Send an e-mail to interluxtechnicalservice@akzonobel.com please include your City/State so we can direct you enquiry to the correct team.
Whether you call or e-mail, please mention your paint guide reference: BW057

You can use our Paint Estimator to determine how much paint is required, based on the type and dimensions of your boat combined with the number of coats required.
How much paint do I need?

Before you change these details

Please be aware that changing this answer will reset any answers below it. If that's ok, click continue.

These filters have been prefilled, based on your previous selections.

How much paint do I need?

We'll help you calculate how much paint is needed.

What product do you want to paint

What type of boat?

Full bodied craft

Fin keeled racing craft

Medium draft racing craft

What is the underwater area?

Hide Formulations Show Formulations

1 x LWL x (B+D) = Underwater Area (m2)

0.5 x LWL x (B+D) = Underwater Area (m2)

0.75 x LWL x (B+D) = Underwater Area (m2)

Abbreviations
LOA = Length Overall
LWL = Length Waterline
B = Beam
D = Draft
F = Freeboard

What application method?

Recommended no. of coats: ?

How many coats do you want to apply?

If you put less than the minimum recommended numbers of coats, it may affect the performance of the coating.

To paint a ? x ? x ? ??, with ? coats

You'll need ? litres of

Warning that this tool is an estimator only

View product

Paint your boat like a pro

Find the best products to keep your boat in great condition

Get all the support you need to paint with confidence

Benefit from our continuous innovation and scientific expertise

Select your country

Our products and guidelines are customised for each country. Please select yours below.

Americas

Asia Pacific

Europe

Middle East & Africa

Who's painting?

Choose one of the following to tailor the site to your needs