Most of us, at one time or another, have left the anchor chain on the bow or tools exposed to the elements—thus opening the door to an oxidation process that leaves us with that familiar nasty rust stain on the boat’s fiberglass. These stains, which are among the ugliest and the toughest to remove because rust seeps into the gelcoat, often form around deck hardware, too. The stains tarnish the areas around cleats, handrails, and stanchion bases.
We rounded up nine products that claim to remove rust stains. Most are cleaners meant for fiberglass; a few also can be used to clean chrome, tile, and porcelain.
What We Tested
We scanned the marine catalogs, the Internet, and the hardware store shelves. Most of the cleaners contain some sort of acid, like oxalic, or hydrogen chloride. Despite their acidic ingredients, some claim they won’t hurt a boat’s gelcoat. Marykate, one of the most popular brands of cleaning products in the marine industry, is one such product. Other household marine names in our test include Star brite, Aurora, and FSR gels (Fiberglass Kreme Cleaner) from Davis. Five of the others are liquid and two are sprays.
The more expensive products are the “marine” cleaners. For instance, prices range from $2.39 for a bottle of muriatic acid bought at Ace Hardware to $12.69 for a can of Boeshield’s Rust Free bought at West Marine.
How We Tested
To promote staining, we placed on the cockpit sole of our test boat several fish hooks, a large crescent wrench, about 10 feet of chain, a rusty old jack stand, and a few other tools. We sprayed the items with salt water several times over the course of two weeks until we had ourselves some real nastiness. Then it was time to clean.
We gave each product a roughly 1-foot by 1-foot section of cockpit to clean. The testers worked from the transom forward to avoid run-off of one cleaning agent getting on adjacent squares. We followed the directions of each, using either a small handheld brush or a white cotton cloth to clean the surfaces.
All of the cleaners instruct the user to let the product sit on the stain, some for as little as 30-60 seconds, some for as long as five minutes. Some call for just a rinsing with fresh water after application, others instruct you to do some scrubbing.
What We Found
The muriatic acid worked the best, leaving only a speck of a rust stain in its square. None of the others completely cleaned the stains in their sections. But some of these products worked better than others, for sure. Four products—all sold as rust-stain removers for fiberglass—made the cut after the first round: Star brite’s Rust Stain Remover (a spray), FSR stain remover (a gel), Power One Rust Stain Remover, and Fiberglass Kreme Cleaner. We tried these four again on a fresh set of stains. It became clear that the longer you let them soak into the affected areas, the better they work. So, to be fair, we applied the four finalists and gave them all five minutes before rinsing.
The Fiberglass Kreme Cleaner cleaned its section, but this blue gel also turned the deck light blue. The Star brite spray cleaned its entire stain, while the FSR and Power One left only trace amounts of stain.
The big question: Should you use muriatic acid—a product not sold specifically for cleaning fiberglass—on your boat?
No, says Mark Hollenback, technical director of the research group at Cook Composites, a major manufacturer of construction resins and gelcoats. “It can cause fading of certain pigments in gelcoat,” he said. The safest way to go is to put the responsibility on the people who produce a product for boats, he said.
PS agrees. Go with one of the products intended for the job. The top fiberglass-specific brand—the Star brite—worked just as well as the muriatic acid when it was allowed to soak for five minutes. It’s our top pick. If the Star brite is not available, we’d get the gel from FSR. The Power One cleaner is the cheapest per ounce, but it’s only available online, so you’ll have to pay for shipping.
Also With This Article
“Value Guide: Rust-Stain Removers”
• Aurora Marine Industries, 905/564-4995, www.auroramarine.com
• Fiberglass Kreme Cleaner, 800/382-9706, www.boatlife.com
• FSR, 510/732-9229, www.davisnet.com
• Instant Rust Out, 800/654-0791, www.ironout.com
• Marykate, 631/244-8550, www.crcindustries.com
• Power One, 315/486-9027, www.fountainofyouthrestore.com
• Rust Free, 800/962-1732, www.boeshield.com
• Star brite, 800/327-8583, www.starbrite.com
• West Marine, 800/262-8464, www.westmarine.com