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Painting the Mast

July 23, 2020

Not all of us have beautiful, pristine masts on our boats. Some of them are, shall we say, “experienced”. Now you could take it to a professional and have them do it. They would probably sandblast or bead blast the mast then apply several coats of Awlgrip primer, sanding between each coat. Then they would apply several coats of Awlgrip paint, again sanding between coats. The resulting mast would be as smooth as a baby’s bottom.
The downside is that it would cost you multiple boat bucks. Depending on what you tell your better half is the value of a boat buck, it will be over a thousand dollars or more. And don’t expect to do this at home. The Awlgrip paints are toxic. If sprayed (recommended) the sprayer must wear protective gear, including coveralls, bunny suit gauntlet gloves and a full hood with outside air supply.  I don’t know about you, but that’s not stuff I have around my shop.

Another mast finishing option is to have the mast re-anodized. Anodizing aluminum builds up a thicker layer of protective aluminum oxide. It won’t make a pitted mast look any better cosmetically and must be done by professionals.
Powder coating is also an option in locations with powder coaters with large (long) enough ovens. In this process, the mast is sandblasted to clean it up. Then epoxy powder is sprayed on the mast. The mast is electrically charged so the powder sticks to the mast. The mast is then baked in an oven which melts the epoxy powder and allows it to form a smooth coating. The powder coating provides a fabulous finish and extreme corrosion protection. Some caveats, though. I had some aluminum port frames powder coated. The first thing the powder coater asked was whether they had ever been it salt water. When I stated the affirmative, he stated that he would not guarantee the finish due to the possibility of salt crystals in the aluminum affecting the powder film. It also is not cheap and must be done by professionals.
However, many boat owners paint their own masts each year, most with great success. In this article, I’m going to state specific products, not because they are the only ones that will get the job done, but because I am familiar with them. Many other products will work as well, but I am not familiar with them.
As with any great paint job the devil is in the details. In this case prep work. Once you have the mast down and on saw horses, at a comfortable height, remove all the mast hardware. This is probably where your first difficulties will occur. Most mast hardware is installed with stainless steel screws or bolts. They will corrode the aluminum mast and make removal difficult. Start by liberally spraying the fasteners with a penetrative spray such as PB-B’laster or Kroil.
The next step is to consider the condition of the mast. In many cases, it will be grey or discolored. In a worst case scenario, it will be pitted. If the mast has been in salt water, there could very well be salt crystals in those pits. Unless scrupulously removed, those salt crystals will be a never-ending source of problems. They will continue to corrode the aluminum and bubble up any finish you try to apply.
If the mast is pitted, sand blasting or bead blasting is probably your best course of action. When the blasting is finished, immediately apply a protective coating. My choice here is Moeller Zinc Phosphate Primer Spray. It is self-etching and will chemically bond to the aluminum to form a corrosion resistant base coat.
If the mast is not pitted and is smooth but dull, sanding will be able to clean the aluminum down to a bright, shiny base. Before sanding, degrease the mast with Fiberglass Solvent Wash 202.  If the mast had been painted before, start with 80 grit sandpaper and change it often, life too short to sand with dull sandpaper. Once you are done with the 80 grit, go back over the mast with 180 grit and then immediately apply a coating of the Moeller primer.
Now comes the decision time. You can use a two-part polyurethane paint; my choice is Perfection. Or you can use a one part polyurethane like Brightside. I have used both with equally good results. Each product has its own companion products, thinners, etc. For best results, I recommend using the companion products from the same manufacturer. Mixing brands is a sure case for paint failure.By this time, you should have a mast with a coat of Moeller primer on it. This product is an etchant and very thin primer, not designed to be heavily sanded. You can lightly sand it with 320 grit to remove any runs or sags, but if you sand through the primer, recoat it.
Next apply Primekote 404 primer. This is a two-part epoxy primer designed for use with Perfection and Brightside paints. After mixing the two parts, add Bush Thinner 2333N, about 25% and apply it to the mast. Lightly sand between coats. Usually at least two coats will be required.
To apply the Perfection, first mix the two parts together and stir well. Let the mix sit for 20 minutes, then thin with 2333N. The exact amount of thinning will depend on temperature and humidity. Be ready to adjust the mix any time. You want a mixture that goes on sm
oothly but doesn’t run or sag excessively.
The application method for either type of finish is the same, “roll and tip”. It will require two people. The first person rolls on a light coat of Perfection. The second person follows behind and strokes out the paint with a dry brush. If the brush gets saturated, throw it away and get a new, dry one. When the two people are working in unison and the thinner is right, the resulting paint layer will smooth out with no brush strokes, runs or sags.
Wait until the first coat is touch dry and recoat. The paint is very thin so at least two or three coats will be required. It provides a very durable finish that should give you 10 to 15 years of service.

One Part Polyurethane (Brightside)
Again, you will be starting with a mast with the Moller primer on it. Apply Primekote 404 as outlined above. Brightside’s is a fairly thick paint as it comes in the can. Do not apply without thinning it (Brushing Thinner 333). A thick coat of paint will flash off the solvents from the surface, leaving the base layer of paint soft and uncured. It is much better to apply multiple thin coats. Sand between coats with 320 or 400 wet or dry sand paper. (here is a hint: if wet sanding, put a couple of drops of dish soap in the water. Works wonders!) On one job, I applied three coats of thin red paint over the primer. Years later, it is still shiny. BTW, one of the reasons I like Brightsides is the range of colors. In addition to various shades of white, you have the choices of Sundown Buff or Bristol Beige, if you fancy a non-white mast.

Finally
Refinishing a mast is well within the capabilities of the average sailor. In addition to the satisfaction of doing the job yourself, you will have saved yourself a bunch of boat bucks.

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