MARINE COATING SYSTEMS
Strafford Morss, Preservation Engineer
MARINE COATING SYSTEMS
Introduction: Most historic ships come from the World War II era, and we are all aware of the immense changes in sensors, weapons, and engineering that occurred. Not so apparent was the impact of the 1940-41 Mare Island Naval Shipyard developed cold plastic anti-fouling paints that were so potent that dry docking periods were extended from every six to nine months to about 18 months. This paint allowed the fleet extensive operational flexibility and overall improved performance and operating economy, compared to the Japanese ships.
Slower to change were the traditional oil and lead based topside coatings. Linseed and later soybean oils were the vehicles. Lead was used in the color pigments, drying agents, and anti-corrosive barriers.
The often weird and unpredictable behavior of the junior enlisted involved in the down-and-dirty preservation work topside and below was attributed to immaturity, combat stress, the "perils of Navy life", and immoderate use of alcohol while ashore. While the above were all surely at work, the extraordinary behavior and health modification aspects (all bad) of the lead and heavy chromium compounds ingested were never recognized. The Navy banned the use of lead in 1980, four years after the FHA.
We have come a long way in coatings technology since then. A thin protective film is big business. The Sherwin-Williams Company, a major industrial coatings supplier, reports that Newport News Shipbuilding uses about 350,000 gallons of coating materials in building a new nuclear aircraft carrier.
Fundamental truisms relative to coatings appear to be:
The coatings that we see today are the:
Anti-fouling paints will not be discussed. For historic ships that do not move, anti-fouling paints are ineffective for over 90 percent of the time between ship dockings, 2007: I now disagree. I was too concerned with saving money to recognize the following: The anti-corrosive coating used (multiple coats of epoxy) will degrade when exposed to continuous ultra-violate light. The epoxy at the waterline and boot top should have been coated with anti-fouling, vinyl would have done nicely and can be overcoated in place, as I understand (but the manufacturer should always be consulted). The anti-fouling should be applied from the top of the boot top to about four feet below the floatation waterline.
The epoxies have a distinct overcoat window before they become too hard to allow adhesion of an overcoat without taking additional actions, i.e., roughing the surface, mist coats, etc., as the epoxy manufacturer may recommend if this absolutely has to be done, but always in the dry. There is now one approved underwater-applied epoxy paint for patching, but even the manufacturer, whom I know on a personal basis, tells me it is only temporary. Use of this coating does not address, or solve, the UV degredation problem.
Today we are privileged to have representatives from two very fine and competent coatings manufacturers, International Paint Company, and Ameron Paint Company.