No Harm, No Foul

Coatings manufacturers roll out new weapons in fight against corrosion.

Jotun Paints’ SeaQuantum line of self-polishing antifoulant paints dates back to 2000 and has gone through several versions. The latest is the SeaQuantum Ultra SP.

Some SeaQuantum coatings are made for worldwide distribution, but the Ultra SP is “designed specifically for the North American markets, where it can cover both the slow speed and layup vessels, up to the medium-range vessels,” said Derick Hayman, marine business development director for Jotun.

For Ultra SP, he defines medium-range vessels with speeds up to 20 to 25 knots. “It would work well for a coastal tug and barge fleet, for cruise boats and for the military where you have long lay-up periods,” Hayman said. Ultra SP is VOC compliant and approved by the Environmental Protection Agency.

Like SeaQuantum’s earlier versions of Ultra, SP is a silyl acrylate self-polishing antifoulant. “It was the first silyl self polishing to be approved in the U.S.,” Hayman said. SeaQuantum antifoulants work by a chemical reaction of the coating with seawater. The chemical reaction that’s produced is similar to “the old tin copolymer types of antifoulant. It mimics it but has no tin.”

That produces a polishing effect that gives a predictable biocide release rate and a predictable polishing rate for the coating. At the same time, Ultra SP prevents slime buildup when a boat is tied up to a dock or moored for long periods. Hayman contrasts Ultra SP’s silyl acrylate with the “standard acrylic resin-based antifoulants that increase roughness over time dramatically and will reduce the release rate of biocide over that same period because they don’t have the polishing effect.”

So even though a boat doesn’t go at a particularly fast rate of speed, the antifoulant benefits of Ultra SP aren’t lost because the silyl-based antifoulant is less dependent on a boat’s movement through the water than others.

That predictability enables Jotun to guarantee a vessel won’t have “more than a certain percentage of speed loss dependent on the actual operating profile of the vessel,” said Hayman. And knowing the boat’s operating profile, Jotun can build a system that provides a five-year antifouling guarantee.

Much of this depends on Pathfinder, Jotun software that’s been used with earlier SeaQuantum coatings. Once an operating profile for a boat is developed, Pathfinder takes that information and provides a film thickness for an Ultra SP application to that vessel.

If you took a roughness reading of the Ultra SP antifoulant coating before a vessel was launched, it might be “a hundred microns,” said Hayman. After a year’s operation, if underwater readings were taken, “you’d probably get 90 microns. That’s the whole concept, to reduce hull roughness and improve your ability to reduce fuel consumption.”

“We can design the system to completely cover the antifoulant needs plus give the customer a much better fuel economy because of controlling the roughness of the hull,” Hayman said.

Ultra SP works with steel hulls. For aluminum, a barrier coat is recommended before application.

POWDER COATING

In 1988, Larry Weidman developed an antifoulant powder coating. However, due to the cost of getting EPA product registration approval, commercialization of the coating was postponed. Then in 2007, Reintjes Marine Surface Technologies, with Weidman as vice president and chief operating officer, was founded to obtain EPA approval and develop an improved plasma thermal spray system. Now, after five years, almost $1 million, and adjusting the coating’s formulation to meet EPA mandates, Reintjes has EPA product registration approval for its new antifoulant thermoplastic powder coating. The Tefcite antifoulant is made up of a polar thermoplastic — Polyamide 12. It’s an antimicrobial material and copper oxide coating that prevents corrosion and cavitation. These powders are delivered with a patented thermo spray system that sends the mixture out in a high velocity gas stream where they become molten in flight and bond together. The velocity of the mixture coming out of the spray system is delivered “at a little under Mach 1,” said Weidman. Mach 1 is the speed of sound. Once on the hull, the coating forms a smooth surface and sets up in less than one minute, he said. There’s 58% cuprous oxide, or copper, in the mixture, but the leach rate is only 1 microgram per square centimeter for 24 hours, said Weidman. “That’s way under what all the state legislatures have recently adopted.” When a boat is hauled and the bottom blasted with a high-pressure water system to clean the hull, that won’t affect the antifoulant. “You can pressure wash it and not worry about the copper and biocides running out and getting into the water,” he said. Tefcite can be applied with a plasma gun or to drydocked steel boats with a thermal robotic drive module that magnetically attaches to the hull and is controlled remotely by an operator who guides the robot around the hull at 500 sq. ft. per hour. Besides being appropriate for a steel hull, Tefcite is OK to use with fiberglass. Because of the copper in the coating, a barrier coating is required for aluminum hulls. It works on both a fast and slow moving hull. The Tefcite thermoplastic powder coating is not something you buy in a five- or 50-gal. can at your local marine supply store. It takes a special thermal spray system to apply the coating. Reintjes manufactures the equipment and the antifoulant materials, but only a boatyard or a very large fleet operation would be able to afford the nearly $300,000 for the equipment. Reintjes is currently lining up licensed contractors.

TEMPERATURE NEUTRAL

A new coating for a completely different application is Heat Flex 3500 from Sherwin-Williams. Instead of going on the outside of a hull, Heat Flex 3500 can be applied to piping and ductwork throughout a boat, especially in the engine room. Introduced in June, Heat Flex 3500 was originally marketed to the oil and gas industry. “Now we are moving into the marine market with the product,” said Ron Knecht, a regional market director with Sherwin-Williams. Heat Flex 3500 is an insulative acrylic coating. It’s basically an acrylic-based resin binder with microspheres as a filler. Those are small beads filled with air that give the coating its insulative properties. When applied to hot piping and ductwork it can do several things. It primarily protects workers from what would otherwise be a hot pipe (up to 350°F) by preventing burns. In cases where heat should be kept in a pipe or tank, it “blocks the flow of energy going out,” said Knecht. The same principle applies if the coating is applied to the walls of the engine room. It keeps heat from migrating into nearby spaces. If you operate in northern latitudes, Heat Flex 3500 keeps water lines from freezing. It also eliminates the need for insulation over pipes, which can trap moisture and cause corrosion.