The right decision about finishing an aluminum mast can be key to your rig’s longevity.
Issue 148: Jan/Feb 2023
Sailboats would be nothing without their sails, but even less without masts to hold them. As shipyards and boat designers continue to move away from the traditional wooden spars, we see forests of aluminum masts popping up around marinas and anchorages, trading varnish for white paint finishes. Although painted masts have a modern, classic look to them, I was curious whether the painting is purely aesthetic or if it has any preventative properties to protect the metal.
The author’s husband, Chris, uses an angle grinder with a 5-inch hook-and-loop sanding pad to remove the mast’s
old paint.
Aluminum is one of the most popular metals for marine use. It is durable, relatively lightweight, and forms an aluminum oxide coating that creates a barrier that prevents the metal from corroding—making it essentially self-repairing. If the metal is maintained and kept dry (which can be challenging on a boat), the oxide will re-form and continue to protect the metal. However, aluminum can become rather rough-looking after years of use and exposure to salt water, so many people often turn to paint. When applied by a professional, paint can last for many years, but if misapplied, the paint can quickly start to fail, creating the potential for problems like corrosion.
If you look at any Coast Guard vessel, you will notice that beyond the signature stripe and bottom antifouling paint, its topsides are all unpainted. The bare metal, utilitarian aesthetic not only looks rugged and saves the Coast Guard costs for paint and maintenance, but also increases the service life of the alloy hulls. Beyond the Coast Guard, owners of other aluminum- hulled vessels frequently embrace the natural oxidation process, allowing the metal to breathe. So why are aluminum masts typically painted?
Prep is Paramount
There is a common misconception that paint prevents corrosion, but it can do more harm than good. Once aluminum is painted, its surface essentially becomes starved of oxygen, making it incapable of developing and maintaining its corrosion-resistant oxide coating. If the paint coating remains intact and the boat’s dissimilar fasteners have a barrier, there should be no issue; with no oxygen and no water present, corrosion can’t occur. However, if the coating is even slightly compromised, it sets the scene for a corrosion cascade, killing your mast’s integrity slowly but surely.
Although paint is considered pleasant to look at, the price for a professional paint job can be an investment. But painting your mast yourself can cause significant issues if it’s not done properly. Be sure to read the paint manufacturer’s instructions before starting any application. Generally speaking, for paint to adhere to aluminum, the surface must be stripped down to oxidation-free bright metal, then immediately undergo a sealant treatment before the aluminum has a chance to develop a layer of oxidation, which will happen as soon as moisture has a chance to settle on the surface.
Mast paint can fail over time, creating the
potential for corrosion.
Properly prepping a previously painted aluminum mast can make painting the topsides seem like a minor operation in comparison, which may be why some boat owners abandon the idea, opting to leave the spar bare or even anodizing it.ÁAnodizing is an electro-chemical process that converts the surface layer of aluminum into a specifi cally structured oxide which is electrically non-conductive and signifi cantly harder than the base metal.
Aluminum oxide is so hard, in fact, that it is commonly used as an abrasive medium—for example, in aluminum oxide sandpaper. The depth of penetration generally determines the quality of anodized coatings. The last step in the anodizing process is the application of a fl uoropolymer sealer which fi lls in the microporosity of the surface resulting from the acid baths used in the anodizing process.
An anodized spar may develop stains and an unsightly appearance but won’t have the rough fi nish of naturally oxidized aluminum. Unfortunately, for us sailors here in California, there are no anodizing tanks large enough to treat masts due to the state’s environmental regulations. So, without the option of anodization, is bare really better?
As mentioned, exposed aluminum will oxidize, which is essentially the metal’s way of protecting itself from the elements. Although more aesthetically rugged, the crispy layer will uphold the integrity of the mast and bare all imperfections, if any, allowing you ample time to react versus waiting to see problems such as corrosion through paint.
Marissa gives a happy thumbs-up to the newly
refreshed mast.
The Sealant Solution
If you don’t like the look of bare aluminum, there are a few tried-and-true products on the market that seal the metal’s pores to protect against saltwater damage, oxidation, pitting, white rust, and black streaks. Products such as Nyalic Clear Coat for fi berglass and aluminum boats help to preserve a boat’s fi nish, and the cleanup of a Nyalic-coated surface is simple, fast, and easy. This boat surface protectant is ideal for aluminum hulls, pontoons, tuna and wake towers, brightwork, lifeboats, in engine rooms, and yes, even on masts.
When it came time to make a decision about our own mast, my husband, Chris, wanted to leave it bare, and although I agreed that I did not want to repaint it, I was concerned about the aluminum looking shabby over time, especially when we’ve put so much work into making our boat shine. After days of research and consulting with industry professionals, we decided to give Nyalic a shot. Chris used a 4-inch roller to apply it and aerosol spray for the harder-to-reach places. He was skeptical about the product’s near-perfect reviews, but nearly a year later, it has held up as well as the day we applied it.
If only the question was as simple as: To paint or not to paint? The many variables involved can make the decision daunting, especially if you don’t have all the facts. Safe sailing isn’t based on aesthetics. Learn the pros and cons of each option and understand what can go wrong. Do your research and consult with professionals to ensure your mast is shipshape and worthy of sailing to new horizons.
Aluminum is a beautiful and stable material. Using the proper aluminum fi nish will dramatically increase the lifespan of your rig.
Chris and Marissa Neely have been living aboard and upgrading their 1979 Cheoy Lee 41, Avocet, since 2018. Primarily they sail in and around Southern California’s Channel Islands. Follow them at svavocet. com, on other social platforms at @svavocet, and on their YouTube channel called Sailing Avocet.
Thank you to Sailrite Enterprises, Inc., for providing free access to back issues of Good Old Boat through intellectual property rights. Sailrite.com
