Here's how you can professionally paint your duck boat including answers to frequently asked questions, step-by-processes for painting both bare aluminum, over existing paint, fiberglass, and additional painting tips.
1. Do I need a sprayer, or will a brush work?
Spraying gives a smoother finish and is much faster than a brush. However I have never desired a mirror like finish on a duck boat as a slightly textured surface from using a brush will help reduce glare from the sun.
2. What type of paint should I use?
Solvent-based or acrylic based can be used. Parker Coatings offers solvent or oil based with Krylon manufacturing both oil based in spray cans and acrylic base in gallon cans.
3. Do I need to sand off the old paint?
If you want the new paint to be perfectly smooth such as the paint on your truck the answer is probably yes. But sanding off original or factory adherent paint on a duck boat is not only a waste of time in my opinion, but will also cost you more money especially when repainting aluminum.
4) Do I need a special primer to paint aluminum?
A regular primer sticks to the material it is applied to by mechanical adhesion. Mechanical adhesion is accomplished by primer settling into scratches created from sanding, and then grabbing onto these scratches it shrinks when drying.
An etching primer is formulated to be put on bare metal such as bare aluminum. This type of primer not only provides a mechanical adhesion, but also a chemical adhesion. The chemical adhesion is achieved by an acid contained in the primer, which etches itself into the material it is applied to. The mechanical adhesion is achieved as describe above in regular primer.
1) Masking tape, 3/4" being most common
2) Masking paper - newspaper will also work
2) Sanding block or power sander
3) 600, 800, 100, 1500, 2000 grit sandpaper
4) Scotchbrite pad
5) Grease Remover - Dawn dishwashing soap and rubbing (isopropyl) alcohol
6) Paper towels
This is the route I would recommend for most situations. Keep in mind I only recommend this method if the current finish is factory original and not peeling or flaking. Because we already have a surface the paint can adhere to versus bare metal, no special primer is needed.
The first step is to thoroughly clean the existing paint with a grease remover as suggested per above. Once dry then remove any gloss with 600 grit sandpaper or a Scotchbrite pad. Even if the existing paint was flat, the existing surface should be scuffed up to promote paint adhesion. The finish should look dull, hazy, or milky.
Next either brush off all surfaces to be painted and then wipe these same surfaces with a rag soaked in rubbing alcohol. After the alcohol has dried you are ready apply 2-3 coats of the color you have chosen, letting the paint tack between coats and then let completely dry. If 2-3 coats are not enough to give sufficient hiding of the "old color", continue with more coats.
Paint should be allowed to cure and harden at least 2-3 weeks.
First step is to sand of the old paint down to bare metal using desired grit sand paper. 80 grit works best for this, it's coarse enough to remove the current finish and only leaves scratches behind that are easily removed. Once all the old paint has been removed lightly sand the surface/s again with 180 grit sandpaper to remove the larger scratches left from the 90 grit. If you want a really smooth finish sand surface/s again with 400 grit sandpaper. Now either use a brush or tack cloth to clean up all surfaces to be painted.
A conversion coating needs to be applied to the bare aluminum. This is most easily accomplished with a self-etching primer and is most easily applied from a spray can or sprayer. Another method is an acid based etching liquid that is applied and then rinsed off with water. In either case local automotive parts stores should have both types available and will also be able to assist you in this process. Be sure to follow all manufacturers' safety precautions when working with these products.
If using the self-etching primer above, once it's completely dry you're ready to apply 2-3 coats of the color you have chosen, letting the paint tack between coats and then let completely dry. If using the etching liquid you're ready to spray down a couple coats of regular primer, letting the primer tack between coats. Next apply 2-3 coats of the color you have chosen, letting the paint tack between coats and then let completely dry.
Once again I would recommend waiting at least 2-3 weeks for the paint to harden before using the boat, otherwise the paint will easily scratch or mar.
To camouflage your boat be sure to read our instructions at Camouflage Duck Boat Stencils And Painting Tips.
Always use a sanding block. You will be much more efficient when using a sanding a block and also will not put deep scratches into the aluminum. You can purchase a sanding block or make one out of about whatever you desire.
Surface preparation is a must to proper paint adhesion. Keep away from silicone products or grease/oil while doing the project. If you have naturally sweaty/greasy hands, it may be a good idea to wear rubber gloves or wash your hands periodically while working.
Prepping is the most important step in any painting project! If you're not going to take your time don't expect any primer/paint combination to make up for your laziness.
Important: It is critical for your own safety to carefully read and follow all manufacturer's instructions and warnings!