An important component of any workboat, one that is often taken for granted until it looks like hell and you realize it can’t be ignored, is paint.
Whether it’s the bright, glossy coating with your company name in large letters painted over it, the coating below the waterline, paint that goes over the bare metal deck, or even a nonskid, it’s something that’s never easy or cheap to replace.
Some recently introduced coatings are designed to save boat owners money in terms of application, maintenance or weight.
In May, International Paint introduced its lightweight Intershield 7100LWT. This works as a deck covering that can be painted over or as an underlayment beneath tiles and carpets.
It is a self-leveling epoxy coating with strong anticorrosion and adhesion properties. When applied to the deck in a ¼-inch thick layer it tips the scales at just 0.8-lbs. per/sq. ft. Many underlayments applied with the same thickness weigh in at as much as 2-lbs. per/sq. ft., according to figures provided by International Paint. That’s a weight difference of 59.5%.
“The whole premise is there’s a lot of interior square footage. This being light it reduces a lot of weight. It can be significant,” said International Paint’s John Mangano.
Intershield 7100LWT is applied without a primer, directly to metal. The application process is fairly easy because of the coating’s self-leveling characteristic. In addition to interior areas including showers and heads, it can also be applied to exterior decking, which is then covered over with paint or a nonskid coating.
A nonskid deck coating introduced to the commercial marine market at the end of the summer is from NCP Coatings Inc. The deck coating was developed at the U.S. Naval Research Laboratory. For the past four years, NCP worked with the Navy, “scaling the product up and developing it into a commercial product,” said NCP’s Randy Terrill.
With an annual bill of $57 million for nonskid deck coatings — that’s just the stuff that comes in the cans, not the preparation or application work — the Navy wanted a coating to replace the traditional epoxy nonskid. It needed to be more durable with a longer service life, which would cut costs over a long time range.
The Navy has been using organic epoxy deck coatings with aromatic epoxy resins. Being organic, the nonskid coatings generally last 18 months and then a new coating must be reapplied.
The new SiloxoGrip, which was first used on Atlantic fleet ships in 2010, is a mixture of inorganic silicone and organic elements carbon, hydrogen and nitrogen. “The silicone part of it is the siloxane base and gives it its durability,” said Terrill. That’s expected to push the 18-month life for the deck coating out to more than 60 months.
One reason for SiloxoGrip’s improved durability is reduced absorption of the sun’s rays. “Nonskid coatings made out of epoxy don’t have good UV resistance,” Terrill said. The nonskid coatings have about 10% to 20% solar reflection while SiloxoGrip’s is closer to 60%. That helps cut the thermal load on other parts of a boat, especially areas below the decks.
Terrill describes polysiloxanes as the next generation of coatings, but SiloxoGrip can be applied with paint rollers, just like older epoxy nonskid coatings, and can also be sprayed on.
What about the paint that covers a boat’s hull and superstructure? International Paint came out with another product in May, Interfine 5703. It’s a high performance, high-gloss finish paint that comes as a single-pack coating.
“Typically most boats use a polyurethane. That’s a two-pack coating,” said Mangano. “That means you have to mix it properly, and traditionally polyurethanes have isocyanates which are carcinogenic.”
The Interfine 5703 eliminates both of those potential problems. Isocyanates are non-existent, and because it’s a one-pack coating, you don’t have to worry about mixing two parts correctly.
Polyurethane paints provide good color and gloss retention but can be wasteful. “Once you mix parts A and B, that’s it,” noted Mangano. “You have to throw the rest out because it will cure in the can.”
Interfine 5703 is an acrylic modified polysiloxane, not an oil-based paint. “That’s the highest performer for color and gloss retention,” said Mangano. “It gives the performance of a two-pack coating, without having to mix parts A and B.”
below the waterline
So what’s available below the waterline? Once a boat is underway, it can be argued that the rudder suffers the most abuse. It’s continually exposed to cavitation erosion — those tiny bubbles coming off the propeller blades that implode against the rudder’s surface, causing pitting and corrosion.
That creates drag, which drives up the fuel bill and maintenance costs. Ecoshield from Hydrex can protect rudders from cavitation damage by eliminating the pitting and corrosion. Hydrex is known for its Ecospeed underwater ship hull coating system. Ecoshield is a specially reinforced version of Ecospeed.
Ecoshield absorbs the cavitation forces with a tough, flexible coating made up of layers of glass flakes in a vinylester resin. There are also proprietary “ingredients that make the vinylester flexible,” said Hydrex’s John Green. “They are one of the key things to its durability.”
Ecoshield is a tough coating, “made specifically for the rudders of icebreakers,” said Green. And from an environmental standpoint, Ecoshield doesn’t have heavy metals or toxic chemicals to leak into the water.
Ecoshield also works well on bulbous bows, stabilizer fins, thruster nozzles and other underwater gear and it doesn’t take long to apply. Only two applications are required with three hours of drying time between each coating.
If it’s an existing rudder with extensive pitting and damage, Hydrex offers Ecofix. This is a vinylester resin product used to fill in the rudder’s pitting and damaged areas. Once the surface has been smoothed over, it’s painted with Ecoshield.
At about $45 a liter (about two liters will cover a square meter) Ecoshield is initially more expensive than other coatings. However, with a warranty that starts at 10 years, the time between recoatings is much greater than with other products.
Ecoshield will remain intact for the lifetime of the vessel. Thus no repainting will be needed during regular drydockings.
According to Hydrex, easy touch-ups of less than 1% of the surface area will be required.
