Maintain Your Metal’s Mettle
STAINLESS STEEL, BRONZE, ALUMINUM—EVEN GALVANIZED: THEY ALL HAVE A PLACE ONBOARD. BUT WHAT KIND OF TLC DO THEY NEED?
We think of modern boats, especially production boats, as made of fiberglass, but even if your boat’s structure is ’glass much of the rest of her is metal. Hardtops and radar arches, bowrails, cleats and chocks, electric horns and spotlights, anchors, the rigging that supports a trawler’s mast—all of it started out as some kind of ore. Fact is, without metal we’d be back in the boating Stone Age. (Does “treenail” ring a bell?) But while metal is often robust, whether it’s stainless, bronze, aluminum, or iron it needs a little TLC once in a while. Routine care is easy, so easy your kids can do it while you enjoy a cool drink on the flying bridge.
When the kids complain that cleaning and polishing hardware takes away from valuable social-media time, explain to them how lucky they are to live in the 21st century, wherein the primary metals on most yachts are corrosion-resistant stainless steel and aluminum. All it takes to keep these alloys happy is soap, water, polish, clean rags, and elbow grease. Washing metal may seem like a fool’s errand, especially to a kid, but it’s the single most important step in keeping the stuff up to snuff: Not only salt, but also dirt will interfere with either stainless steel’s or aluminum’s corrosion resistance, which both rely on the free flow of oxygen across the surface.
THE CHROME STANDARD Stainless steel for marine use is an alloy of low-carbon steel, chromium, (about 18 percent) and nickel (about 8 percent); this is the basic Type 304 stainless, sometimes called “18-8” stainless. Stainless steel fastenings are usually 18-8 alloy. Type 316 stainless contains a bit more chromium and about 3 percent molybdenum for better corrosion resistance at the cost of a little strength;
BY MIKE SMITH
it’s used for deck hardware and underwater applications. But whatever the alloy, it relies on oxygen combining with the chromium to form a microscopically thin surface film of rustresistant chromium oxide. The oxide layer is easily damaged, but it re-forms as long as there’s oxygen present. If the oxygen is blocked—for instance, by encrusted salt, dirt, or a combination of the two—the oxide layer can’t regenerate, and before long the surface shows tarnish.
If left untended for a long, long time, the stainless will corrode away, more likely on components that are out of sight, like fastenings for deck hardware: Water seeping under deteriorated bedding attacks the oxygen-starved stainless and eventually something gives. So, whenever you see tarnish stains on fastenings, investigate further. Rebedding the hardware and replacing the fastenings is easy.
Maintaining stainless steel is even easier: Keep the salt and dirt off. Whenever you wash down, clean the stainless thoroughly with soap, water, and a sponge or rag—use a toothbrush to get into corners and angles. Remove any tarnish with an appropriate marine cleaner and polish (the chandlery is full of them), then polish again periodically. Even this rudimentary maintenance will keep your stainless steel looking great for years.
CONTROLLED CORROSION Aluminum also protects itself by combining with oxygen to create a surface layer of aluminum oxide, and it’s often given a head start during manufacturing by anodization, basically controlled galvanic corrosion: The aluminum acts as the anode in an electrolyte bath, and when electric current is applied it picks up oxygen from the electrolyte to form an aluminum-oxide surface layer. The anodized surface is corrosion-resistant, durable, and easily maintained. Color can be introduced during anodizing, or the metal can be painted afterwards; anodized aluminum holds paint very well. Or you can just leave it bare.
Once placed in service, the aluminum oxide coating repairs itself by interacting with oxygen in the air, just like the chromium in stainless steel. And therefore it’s just as important to keep the metal clean so you maintain its natural corrosion protection. Washing your aluminum whenever you wash your boat will keep its anodized surface looking good for years, especially if you wax or polish it every now and then. Again, there are lots of products on the market, but many folks I know rely on Woody Wax ( www.woody-wax.com), an easy-to-apply elixir that you just wipe on and let dry; you don’t have to buff it off, so you’ll be more inclined to use it often.
The 6061 aluminum alloy (more than 95-percent aluminum combined with small amounts of magnesium and silicon, plus traces of copper and chromium) used for most onboard aluminum rails, hardtop frames, arches, masts, and so forth—is