Marine coating developers try to cover all the bases

Capt. Jack Sparrow must have had a hard time keeping barnacles off Black Pearl in his days as a pirate of the Caribbean, probably getting by with a simple scraping and painting. By comparison, today's commercial shipowners have a serious headache when it's time to repaint their hulls.

That's because they're trying to balance several objectives: complying with environmental regulations for both water and air pollutants, minimizing time in dry dock and maximizing fuel savings.

To address their needs, new coatings have proliferated. Some are antifoulants, which work by releasing active ingredients in the paint upon contact with water. Others are fouling-release coatings, which maintain an exceptionally smooth surface that keeps the hull free of foulants.

"To a shipowner it's a little bewildering because there are so many new technologies and so many new claims being made," said Michael Bentkjaer, Sherwin-Williams's global market director for marine coatings. "Because the market is moving so fast and because polymer chemistry is making advances rapidly, I think they are relying on their supplier to educate them."

{C}This ship was recently coated with Sherwin-Williams SeaGuard HMF antifoulant, which debuted in December 2008.

Within the past year, Sherwin-Williams has introduced coatings in both product categories. SeaGuard, an antifoulant free of heavy metals, received Environmental Protection Agency approval last summer. Sher-Release, a silicone fouling release coating system, was introduced this spring.

Other manufacturers have been equally busy. International Paint's Intersleek 900 is a fluoropolymer foul release coating designed for vessels traveling at over 10 knots that the company claims has resulted in savings of up to 6 percent on an Aframax tanker. Hempasil X3, a new antifouling coating that developer Hempel says fools organisms into thinking the ship's hull is liquid, won an award this spring from an engineers' society in Denmark.

U.S. paint giant PPG Industries, whose brands include Amercoat and Sigma Coatings, recently announced a contract to supply coatings for the entire fleet operated by the U.S. Navy's Military Sealift Command.

{C}A closeup of a newly painted hull.

Of all the concerns that today's coatings are expected to address, perhaps the least controversial, at least in the United States, is environmental. That's because U.S. shipowners, prompted by state and federal regulators, tend to be ahead of the pack. An international convention to regulate harmful antifouling systems was adopted by the International Maritime Organization and went into force last fall, but it caused scarcely a ripple here. Kathy Metcalf, director of maritime affairs for the Chamber of Shipping of America, says that was because shipowners anticipated it.

Nevertheless, concerns about the impact on the marine environment from hull fouling may soon replace those about the more publicized dangers from ballast water discharge. "Hull fouling is going to be one of the biggest impacts we face in the next 10 years," Sean Connaughton, the Bush Administration's maritime administrator, told the Global Greenship conference in Washington, D.C. last fall.

Concerns about copper are causing manufacturers to look for alternatives to cuprous oxide in paint. The U.S. Navy has a mandate to reduce the amount of cuprous oxide it emits from its vessels. Researchers in Sweden — concerned that an estimated 40 tons of copper are distributed along the nation's west coast every year — have been working with International Paint to develop an antifouling paint with a biocide that targets only the organism it is aimed at, so that only tiny amounts are released into the water.

Sherwin-Williams's SeaGuard antifoulant was created to meet the same concerns. "We're looking for biocides that degrade very rapidly in nature so they don't stay in the bottom sediment for years or decades, which is the case with heavy metals," Bentkjaer said. (Another plus for biocides over cuprous oxide: the paints weigh a lot less, saving shipowners money.)

Meanwhile, clean-air legislation has had its impact on the coatings industry as well. Manufacturers face limits on the solvents they can use and on hazardous air pollutants. "We are certainly moving towards higher solid materials, even toward 100 percent solid materials, because the emission of solvents — VOCs (volatile organic compounds) — has been a big issue in the U.S.," said Bentkjaer. "I think it's for the benefit of all of us that we limit the amount of solvents that go up in the clear blue sky."

And surface prep is far different from the bad old days. "Here in the U.S. several years ago we started to move away from abrasive blasting, which had been the norm for many years, and went to water jetting," said Bentkjaer. "So we had to come up with products that were suitable to be applied over a surface that had been water jetted." At the same time, shipowners pressed for coatings that dried fast and could be applied in fewer coats. "It was a labor cost and time issue," said Bentkjaer.

Of course, fuel savings from cleaner hulls have been a central concern recently, especially during last year's spike in prices. That has been one of the movers behind new developments in fouling release coatings such as Sher-Release.

"One of the things that has been said about these foul-release coatings based on silicone is that they have been mechanically weak, so if they hit something in the water they would be damaged rather easily," Bentkjaer said. "But the product that we have, our tests show it's a more durable, tougher type of coating."

"It used to be we had to keep the hull of a ship free of fouling," Bentkjaer added. "Now it's moved one step further: not only does it need to be kept clean, but it also has to be kept smooth, because in that way we can reduce the fuel consumption. That is something that has been tied into these new silicones that are being used for fouling control. We don't call them antifouling, because they don't prevent fouling, but if fouling occurs, they clean up very easily — just the friction through the water will keep the hull clean."

In today's economy, some ships aren't moving through the water at all. Some newbuilds are going straight into lay up and existing vessels are being idled.

Paint maker Jotun has an answer for that, too. In June, it introduced SeaQuantum Static, an antifouling paint whose composition and biocidal properties are designed for vessels headed for lay up, especially in warm or fouling-intensive waters. Jotun is looking on the bright side, saying its paint is also suitable for "owners who need to prepare the vessel for rapid re-entry into the market." •

Left, this ship was recently coated with Sherwin-Williams SeaGuard HMF antifoulant, which debuted in December 2008. Inset, a closeup of a newly painted hull.
Photos courtesy Sherwin-Williams Co.
This illustration shows Axel Spirit's track line from its anchorage as the crew attempted to pass Ambrose Light. The vessel struck the light tower, and investigators concluded that the master never plotted his intended course.
Ginny Howe illustration/Source: NTSB
Island Providour I, which sank in British Columbia's Sunderland Channel, is shown here at a Campbell River dock after the vessel was salvaged.
Michel Drouin

By Professional Mariner Staff