In the near future, crewmembers on board U.S. Navy vessels will have an easier time keeping their footing on decks awash with seawater, thanks to the work of scientists at the U.S. Naval Research Laboratory (NRL).
In a 2010 test, the NRL-developed siloxane nonskid deck coating (on the right side of the picture) is compared with traditional epoxy nonskid deck coating (left side) six months after application for resistance to wear, and discoloration from daily use and exposure to the sun and sea on board the U.S.S. Mason. The siloxane coating has retained more of its more of its original color, and nonskid texture. (Photo courtesy of U.S. Naval Research Laboratory)
A new nonskid deck coating developed at NRL, and now undergoing final development and ship testing, promises to be more durable, hold its color longer, and be more resistant to spilled chemicals. Because the new material, called siloxane, will last longer compared with traditional nonskid deck coating, it will also be cheaper in the long run.
With approximately 250 ships, 11 of which are aircraft carriers, the Navy has nearly 5 million square feet of deck area, including walkways and carrier flight decks to cover. The annual bill for "nonskid," as it is called in Navy parlance, comes to about $57 million annually, which does not include the cost of labor, power removal of old deck coating, and other considerations.
John Wegand with NRL’s Center for Corrosion Science and Engineering says that the goal is to develop a functional coating that works better than current epoxy nonskid that has been in use on naval vessels for decades.
“We have a material that’s going to be more durable, and have better service life than the current epoxy nonskids that are out there,” he explains.
The siloxane nonskid coating is made up of both inorganic (silicone) and organic (carbon, hydrogen and nitrogen) materials. The inorganic components help with durability, and also improve resistance to the harmful effects of ultraviolet light (UV).
Epoxy coatings currently used on Navy ships, on the other hand, are primarily organic in nature, composed of aromatic epoxy resins that are mixed together, and then applied over an anti-corrosive deck primer paint. The organic nature of traditional deck nonskids give them an 18-month operational life, after which they must be reapplied. The new siloxane nonskid, by comparison, is projected to have a service life of more than 60 months before it will need to be reapplied.
Dr. Erick Iezzi, an NRL researcher who led development of the new nonskid product, says his unit was given the assignment to develop the new product by NRL’s parent organization, the Office of Naval Research, after a better coating was deemed to be a top priority for the fleet. He says the siloxane nonskid is the result of about 6 months of laboratory development in 2009, with the first shipboard trials taking place in 2010, primarily on Atlantic fleet ships based in Norfolk, Virginia.
Iezzi says a big priority in developing the new siloxane nonskid is that it apply in much the same way as the current epoxy-based coating. “We wanted to substitute the material into the fleet,” he explains, “and not have to retrain everyone currently applying nonskids to ships.”
Traditional epoxy nonskid can only be applied to decks with standard paint rollers. The new nonskid also can be sprayed on, cutting application time, because it is less viscous than traditional nonskid.In addition, siloxane is easier to clean, since it has better porous resistance to liquids containing hydrocarbons, most often the material that is spilled on decks during normal ship operations.
NRL’s James Tagert helped establish and supervise the testing program for the siloxane nonskid. He says this involved applying the new coating alongside the epoxy nonskid on the decks of working navy vessels.
“We test for things like adhesion to the primer,” he explains, “the coating’s coefficient of friction or resistance, durability or wet-wire resistance to abrasion, and exterior durability to ultraviolet light.”
Tagert adds that along with demonstrations on Atlantic fleet ships in Norfolk, demonstrations have also taken place on Pacific fleet vessels based in San Diego, California. To date, eight Navy ships have taken part in the testing program.
The development program for the siloxane nonskid coating is expected to continue into the next fiscal year. “We are finishing our qualification testing,” Tagert says, adding that they are also continuing development to further refine the nonskid product.
“We want to reduce solar absorption, and also look at it as a direct-to-metal application,” he explains. Traditional epoxy nonskids are currently applied over a separate anti-corrosive primer. Tagert says in an effort to improve the long-term durability, they are testing the siloxane nonskid with new primers developed for Navy use in other parts of ship operation over the last several years.
Reducing absorption of the sun’s rays is important, Iezzi explains, because dark colored nonskid makes ship decks hotter, increasing the thermal load on other parts of a ship, especially operational areas below those decks.
“Many of the nonskids currently in use have a 10-20 percent solar reflectance,” he outlines. “We’re trying to increase that threefold, and give the Navy a nonskid that will reflect 60 percent” of the sun’s rays.
NRL is developing the siloxane nonskid under a nonexclusive license with NCP Coatings, Inc. of Niles, Michigan.