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How to fully paint bare steel / cast iron

Paint Guide AW098
 

  • I am going to work on a surface above the waterline change

  • I want to paint my boat change

  • I want to do a full paint or repaint change

  • I am going to paint my bilge change

  • The part I want to paint is steel / cast iron change

  • The surface is bare change

  • The surface is showing no defects change

Paint job at a glance

Here's your custom paint guide

Before any project, take these things into account to get the best results:

  • Factor in enough time for each stage of your project so you don't have to rush.

  • Always check the weather while planning your project. Temperature, humidity and dew point affect the quality of your work.

  • Check you have all the equipment, tools and products you need.

  • Ensure you read all the information in the health and safety tab above.

Equipment we recommend for this guide

Equipment List 2
  • Rubber gloves

  • Dust mask

  • Sanding paper 120 - 180, 320 - 400 grit (various grades for primer application)

  • Sanding paper 320 - 400 grit (various grades for topcoat application)

  • Paint roller tray

  • Paint rollers (suitable sizes and types)

  • Paint brushes (suitable size)

  • Tack rag or lint free cloth
Equipment List 3
  • Safety shoes

  • Face dust masks

  • Hand protection (as per product SDS)

  • Overalls

  • Sanding machine and/or suitable sanding blocks

  • Eye protection

  • Specialized cleaning product

Your health and safety

Your safety is of the utmost importance to us. Ensure that you read and follow all label instructions and the safety datasheet before starting your project. Also:

  • Ensure the area you are working in is properly ventilated.

  • Ensure all products are kept out of reach of children during storage and usage.

  • Ensure solvent fumes and any splashing of material will not affect others nearby.

PPE (Personal Protective Equipment)

Before you begin, always refer to the label and safety datasheet for product specific information. Using the right PPE for your project is important to ensure your safety. You should always check the information from the PPE manufacturer to ensure you use the correct items for your working conditions.

  • Wear safety glasses at all times to protect your eyes from splashes.

  • Chemicals can cause skin irritation. Wear overalls and protective gloves to protect your skin and clothing.

  • To avoid inhalation of dust while sanding; wear a dust mask at all times.

  • Many products contain either solvents or other chemicals that can build up in confined areas creating a hazard and/or an unpleasant working environment. Wear suitable respiratory protection if ventilation is not sufficient or if required by the safety datasheet to do so.

See the protective equipment overview for further information.

We care deeply about the environment and we want to ensure that our products are disposed of in the correct way. With that in mind, please:

  • Always refer to the product label and safety datasheet for any specific instructions.

  • Ensure any waste product including cans, rags, brushes, roller sleeves masking tape and paper, gloves and overalls are disposed of according to local regulations.

  • Do not allow any waste material such as unused paint to enter any waterways.

  • Ensure waste and empty containers are disposed of in accordance with local legislation guidelines and national regulations.

For more information or any special waste regulations, please contact your local waste regulation authority.
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Step 1 Cleaning bare steel / cast iron

1.1 Rinse

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

1.2 Degrease

  • Degrease the surface with a specialized cleaning product.

1.3 Rinse again

  • When using a water soluble cleaning product, rinse the surface with plenty of fresh water. However, it’s important to avoid using too much water on bare cast iron as it is porous and can 'soak' into the metal leading to corrosion when your boat is in use.

  • Allow the surface to dry.
Show tips from pros
  • 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.

  • 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.

  • 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
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Step 2 Sanding bare steel / cast iron

2.1 Sand

  • Sand well using an abrasive disc (24-36 grit) to achieve a heavily scored surface profile.

2.2 Remove particles

  • Remove any sanding residue with clean compressed air, sweep the surface with a clean brush, or vacuum clean for best results.

2.3 Application

  • The first coat of primer on bare steel should be applied within 4 hours after you’ve finished the sanding (or blasting).
Show tips from pros
  • Corrosion materials / rust will start to form in the presence of air and water so the sooner steel can be overcoated after preparation the better.

  • Power grinding is the most effective way to prepare bare steel.

  • Be careful not to sand over the sealants around windows or fittings as the sealant can contaminate the surface. Cover these areas with masking tape before sanding.

  • Grit blasting is the best way to prepare bare steel as it provides an ideal profile for paint adhesion. Grit blast to Sa 2½ to a near white metal surface. This should be done by a professional.
Show equipment you'll need
  • Cleaning brushes

  • Sanding paper 24-36 grit (various grades for surface preparation)

  • Vacuum cleaner (or compressed air)

  • Cleaning thinner

  • Rubber gloves

  • Dust mask

  • Overalls

  • Sanding machine and/or suitable sanding blocks

  • Eye protection
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Step 3 Applying primers

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.

3.1 Mask off

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

3.2 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.

    • 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 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.

3.3 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.

3.4 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, 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.

  • Product performance is based upon the film thickness, so please make sure the recommended number of coats are applied.

3.5 Final sanding

  • Once all the primer coats have been applied and cured, sand the entire surface using 180 - 240 grit paper. Make sure you don’t expose any substrate. If you do, you’ll need to re-prime those areas and feather the edges back in once it’s cured to avoid the edge of the patch showing through to the final finish.

3.6 Clean surface

  • Dust down with a lint-free cloth or suitable tack rag.

  • If there is any risk that the surface has been contaminated with oil or grease (e.g. fingerprints), wipe with a suitable thinner prior to applying the undercoat.
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 5-6 mm 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 75-150mm 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.
Show equipment you'll need
  • Sanding paper 120 - 180, 320 - 400 grit (various grades for primer application)

  • Paint roller tray

  • Paint rollers (suitable sizes and types)

  • Paint brushes (suitable size)

  • 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
Cookie Settings

Step 4 Applying topcoat finishes

4.1 Mask off

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

4.2 Mixing

  • Single pack products:
    • With single pack topcoats, 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 topcoat, mix the individual components thoroughly.

    • Combine the two products and mix the paint thoroughly as indicated on the datasheet or the label on the can. Two pack products have a limited pot life when mixed. Refer to label or technical data sheet for further information.



  • It is usually necessary to add solvents to aid application or improve flow. For the recommended solvent and the amount you need to add, please refer to the datasheet or the label on the can.

4.3 Wipe down

  • Wipe the surface with a tack rag to remove all final traces of dust.

4.4 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.

  • Taking one or two square metres at a time, paint the masked off edges or difficult areas with a small brush first.

  • The best method for applying topcoat to a larger area is by using a roller to apply it to the surface, and use a brush at a 45 degree angle to smooth out the wet paint (this called the roll and tip method).

  • 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.

4.5 Overcoating

  • If any of the coats you apply develops runs or sags, or has contamination in it that needs to be sanded out, use 320 grit.

  • You can apply the next coat within the recommended overcoating time.

  • For the best aesthetic results, we recommend a light sand between coats.

  • If you exceed the maximum overcoating time, you must sand the surface with 320-400 before applying the next coat.

  • If the surface has been sanded, wipe with a tack rag before applying the next coat.

4.6 Finishing up

  • 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.

  • After the final coat, remove any masking tape whilst the paint is still wet. This will give you a clean painted edge.

Important:

  • It is possible that the repaired area may show a colour difference when compared to the original finish* To minimise colour differences, try and carry the repainted area out to defined panel edges or join lines; for example if you have repaired a transom then you could repaint the whole transom. If you are repairing a hatch repaint the whole hatch.

  • If you have made a patch repair on one side of a hull only, then you might be faced with repainting all of that hull side as there are unlikely to be any suitable edges.

  • It is not recommended that DIY painters attempt to cut and polish the edges of a repaired area. Doing so would lead to irreversible damage to the finish resulting in premature loss of gloss and possibly a greater colour change over-time. Products that are capable of being cut and polished are generally for professional use only.
Show tips from pros

Working with a roller:

  • Applying paint with a roller is a fast method of covering large areas

  • Rollers should be high density closed cell foam types to minimise formation of bubbles that can occur with mohair or large cell foam rollers.

  • 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 should be medium to large width typically 75 – 150mm with long flexible bristles.

  • A smaller 50mm brush will be used for painting around windows or any other fiddly detail.

  • Wash your brushes with the thinner and dry them thoroughly before using to avoid contamination.

  • When applying by brush, clean or change brushes after 20 minutes to avoid overloading with paint.

  • Use a worn brush if possible for the final coat to ensure less brush marks.

  • When tipping-off with a brush, put some thinner inside a container to clean the tipping brush should the bristles start to clog due to curing or thickened paint.

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.

  • If you’re getting runs as the paint is applied then it’s either too thin or you’re applying too much. If you’re seeing runs/sagging that occurs after 5-10 minutes, the paint is too thick and needs to be carefully thinned.

  • Always use lint-free cloths/ tack rags.

  • Never paint wearing wool clothing as the fibres can find their way into your work.

  • Avoid using paint direct from the can as this may introduce contamination and prematurely age the paint from solvent evaporation. Pour the amount you expect to use in 30 minutes into a separate container.

  • You may find some old jam jars or clean dry tin cans are useful for mixing paint. Also metal measuring spoons of various sizes from the supermarket are ideal for measuring small quantities of paint and hardener for the smaller jobs.

  • Normally 2 - 3 coats of finish coat will be needed. After the first coat, assess how much product you used to help you work out how much you'll need to complete the job. Refer to label data for self-on-self re-coating times.

  • Finishes can be applied using a brush and/or roller. stir and leave the mixed paint for around 10 minutes to allow bubbles to disperse.

  • On a hull, it’s best to have two people working side-by-side. One applying vertically by roller and the second following along tipping off vertically with a brush whilst the paint is still wet enough to retain its wet edge.

Show equipment you'll need
  • Sanding paper 320 - 400 grit (various grades for topcoat application)

  • Paint roller tray

  • Paint rollers (suitable sizes and types)

  • Paint brushes (suitable size)

  • 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

We're here to help

We're ready to help. Our friendly help desk is open weekdays 8:00 - 16:30
Call 01489 775062
Send an e-mail to iyp.uk@akzonobel.com
Whether you call or e-mail, please mention your paint guide reference: AW098

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