Collier, Ev."Antifouling answers: foul-release paints can reduce your fuel consumption by up to 10 percent."National Fisherman.90.1(May 2009):32(2).General OneFile.Gale.Cape Cod Regional Technical High School.13 Sept. 2010
Full Text:COPYRIGHT 2009 Diversified Publications
Estimates of excess fuel consumption caused by fouling of the bottom of a boat range from 10 to 40 percent.
But even if you have a fresh coat of antifoulant, don't think you aren't in that group throwing away money on wasted fuel. A study by the U.N.'s Department of Fisheries and Aquaculture estimates that bottom fouling increases fuel consumption up to 7 percent one month after the paint is applied and 44 percent after six months.
Increased fuel consumption translates into increased spending by the boat owner. In November 2006 the price of diesel fuel in Florida was $2 per gallon but by July of 2008 it was $4.72 before dropping to $2.25 in November.
In Alaska, prices were averaging $3.20 in January 2008; $4.60 the following July and $3.87 this past December. Fishermen in Alaska are obviously paying more than fishermen in Florida, but even at $2.25 per gallon, burning an extra 10 percent or more of fuel each day is not a good way to try to turn a profit. And make no mistake about it, those schizophrenic fluctuations in fuel prices, superimposed on a steadily increasing base price, will return.
Paint companies have been turning their attention to coatings that are easier on the fuel bill, but for years the main focus of bottom paint technology has been to meet the objections of environmental groups and government agencies. And as it turns out, a benefit of the quest for environmentally friendly paint is bottom coatings that might reduce fuel consumption,
When you look back a bit at what boat owners have used to keep marine organisms from taking over a boat's underwater surface, you find antifoulant coatings that incorporated such toxicants as mercury, lead, cadmium, tin and even arsenic, not to mention a whole list of unpronounceable chemical biocides including DDT--dichlorodiphenyltrichloroethane.
These heavy metals and biocides have reputedly killed or made awfully sick many species of marine organisms. Organotins, which are compounds of tin, are credited with the collapse of the oyster fisheries in Arcachon Bay, France and caused severe cases of gender confusion in whelks, a large marine snail commonly eaten in Europe.
Most bottom paints with any of these ingredients have been discontinued, leaving us just copper in its various forms: cuprous oxide, copper thiocyahate and metallic copper. However, copper-based bottom paints are currently under intense scrutiny by environmental agencies.
Take the case of the Port of San Diego, which under a grant from the U.S. Environmental Protection Agency is currently conducting a two-year project designed to identify safer alternatives to copper-based antifoulants.
Copper has been identified as a water quality problem in San Diego Bay marinas, and a 76-percent reduction in copper by 2020 has been imposed that places strict limitations on the use of copper-based antifouling paints. The objective of the study is to identify non-copper bearing paints, not necessarily non-metallic or non-biocidal coatings.
Some 46 coatings from 23 manufacturers were submitted for the first phase of the study where test panels were submersed in the water. This phase of the project has been completed.
The next testing phase begins in April and will be an evaluation of the 19 coatings that successfully completed the first phase. This time the paint will be on the bottoms of boats.
Of the coatings submitted, 39-percent were zinc-bearing (zinc oxide and zinc pyrithione). Nine-percent contained some form of proprietary biocide, and the remainders contained neither metals nor biocides.
ePaint and Pettit were two of the coatings being tested that contain neither metals nor biocides. These are copperless coatings that use Zinc Omadine, an antimicrobial agent approved for use by the EPA and commonly found in dandruff treatment lotions.
Another antifoulant in the test containing neither metals nor biocides is foul-release paints from International Paint and Hempel. It's that type of bottom paint we are primarily concerned with here.
Foul-release paints can save 8 to 10 percent or more on fuel costs, and, depending on the surface preparation, have a service life of five to 10 years before recoating. That's with no hazardous materials to inhale, wallow around in or dispose of. According to the advertising claims of the major suppliers of these coatings, that's about what you can expect.
Foul release coatings are typically based on polymer compounds that produce super slippery, low surface energy finishes that dramatically diminish the ability of fouling organisms to adhere to it.
The working principle is strictly physical, as opposed to chemical. The paint's low surface tension simply releases the fouling organisms as a result of water flowing along the hull as the boat is moving. Any organisms that do remain attached when the boat is idle for extended periods are not firmly affixed to the hull and are easily removed, whether by the movement of the vessel when it gets underway or by wiping with a soft brush.
The concept of super-slippery foul-release coatings is not new; it goes back to 1977, when the first patents on the technology were issued in the United Kingdom and in the United States. But it was not until 2003 that the technology looked like it worked. That was 10 years after International Paint did a full-ship bottom coating of its Intersleek on Tropic Lure, a 2,563-deadweight-ton roll-on, roll-off cargo ship.
After 10 years of service in the warm waters around Florida, where the bottom of a boat can easily be covered with marine growth, the Tropic Lure was dry-docked and found to have only an easily removed slime coat on the bottom with no macroalgae or barnacles.
The vessel had been hauled once in 1995 and again in 1998 and given only a high-pressure washing and repairs to damaged areas. Shortly thereafter, Hempel A/S introduced its Hempasil foul-release coating system, and in 2005, Jotun entered the fray with its SeaL-ion product.
All paint manufacturers were reporting reduced fuel costs; the most frequent savings mentioned being 10 percent. Additional benefits include increased speed, reduced maintenance and five or more years between re-coatings.
The paints fell into two categories: those for high speed vessels with operating speeds of 30-plus knots and activity levels of at least 50 percent or more, and those with service speeds above 15 knots and activity levels over 75 percent
Those coatings worked well for large vessels such as fast ferries, container ships, tankers, and cruise liners, but they were just a matter of interest--and possibly envy--for commercial fishing boats with slower hulls and very different activity profiles.
However, time marches on and the inevitable technology advances occur, and lo and behold, maybe it's time to take another look at these coatings.
In March 2007, International Paint introduced its third- generation foul-release system, the fluoropolymer-based Intersleek 900, and Hempel brought out its third-generation Hempasil X3. (Sherwin-Williams is about to release its SherRelease paint.)
These paints work with operating speeds as low as 8 knots and activity levels down around 50-percent. That clearly puts them within the range of commercial fish boats.
The foul-release paints are multicoat systems. If you are looking for a 10-year service life, all the existing bottom paint has to be removed, down to the bare hull. Then one or two epoxy anti-corrosive coatings are applied, followed by a proprietary tiecoat and finally the foul-release topcoat. (The tiecoat is the key here. It binds the anti-corrosive coating to the topcoat and without it, the foul-release paints won't work.)
If you want to avoid the expense of blasting the hull down to its bare surface, the tiecoat and topcoat may be applied over conventional self-polishing copolymer bottom paints. But you will only have a maximum five-year service life.
Hull smoothness is crucial to the coating's performance. So the coatings must be applied according to the manufacturer's instruction using airless spray and strict control of film thickness.
The average hull smoothness of a conventional antifouling paint (That's the difference between a paint area that's perfectly smooth and nearby bumps and nodes.) is typically in the range of 125 to 150 microns (a micron is one millionth of a meter or 0.00004 inches).
After taking a hull down to its bare surface and then applying the coatings, the average hull smoothness for a properly prepared foul-release coating is on the order of 20 microns, so the application process is critical. However, this is a onetime cost, subsequent recoatings after 5 or more years consist only of repairs to damaged areas and a fresh topcoat.
Now comes the caveat to foul-release coatings: cost. These paints are not cheap. You can expect to spend between $500 and $600 a gallon.
Based on discussions with suppliers of these coatings--not for attribution, as celebrities and other "knowledgeable sources" are wont to say--I've put together a couple of mathematical examples of applications (see "Are foul-release paints for you?") to provide a rough idea of whether an investment in foul-release paints can pay off and how long it would take.
The numbers I've used are only my guesses; nobody knows your operating profile better than you, so feel free to plug your own numbers into the equations.
Lastly, research work carried out in the New Zealand fisheries found the major causes of fuel inefficiency to be, in order of importance:
People--primarily the vessel operator
Propellers--incorrect diameter or pitch
Engines--mismatched to the gearbox or propeller
Notice that the skipper is the most significant factor in the system. So, after improving your fuel efficiency with some expensive bottom paint, you could easily cancel out any fuel or cost savings through an injudicious use of the throttle.
Are foul-release paints for you?
Justifying the expense of foul-release paints isn't complicated but it can be a chore, as it involves calculating fuel saving over time.
Factors in this calculation are the cost of paint and its application as well as your expectations about the price of fuel and how much you will burn--or more importantly, save over the life of the paint job.
For help in making this calculation, go to
Ev Collier owned a marine electrical installation business. He wrote "The Boat Owner's Guide to Corrosion."
Gale Document Number:A197597679