Re: Dupont Imron over bottom paint?
This should help - long and short is some are made to come off so I doubt you could paint over it with good results. This is from West Marine Advisors<br /><br />How antifouling paint works<br /><br />They all contain biocides, chemical agents that hinder or repel unwanted underwater life. Most contain copper compounds combined with other substances for particular characteristics. Some antifouling paints maintain a level of biocide near the hull surface, which deters growth from adhering. Some paints and coatings rely on their inherent "slickness" to prevent growth from sticking.<br /><br />Ablative Anti-foulings<br /><br />Ablative paints wear down like a bar of soap when water passes over them. The abrasion created by the hull moving through the water reduces the paint thickness, exposing fresh layers of biocide to the surface throughout the boating season. Although the wear happens in a controlled fashion, it will wear off faster in higher drag areas on the hull and appendages. This paint works well in high-growth areas and continues to be effective after haul-out and re-launch. Because ablative paints expose new biocide until worn completely away, additional coats add to their longevity. We recommend the application of three coats. Ablative paints with anti-slime additives are best for heavy fouling areas. A practical side of ablative anti-foulings is that they can be applied over most other types of antifouling paints.<br /><br />Best use: On boats that are used often, but not serviced by a diver. Not recommended when you want a super-smooth bottom finish and have a diver maintain it since scrubbing removes paint and reduces longevity. Ablative paint is not the best solution for boats that are hauled and re-launched without a new bottom job like trailer boats and boats that are stored seasonally. Also, this type of paint requires thicker coats, which means more weight and more money since you need more product.<br /><br />Hard Anti-foulings<br /><br />If you like to go fast, you are most likely a candidate for a hard antifouling paint that leaches biocides upon contact with water to prevent marine growth. As the season wears on the paint will become less and less effective, because it "runs out of ammunition," meaning the amount of biocide it releases will decrease. When all the biocide is used up, the thickness of the remaining paint is still the same as it was at the day the boat was launched (a difference to ablative paints). Some hard antifouling paints have Teflon added to reduce surface friction. These products resist scrubbing and abrasion, making them ideal for avid racers who have their boat's bottom regularly scrubbed. They also can be wet sanded or burnished for super smooth surfaces that produce very little drag. On the down side, they are incompatible with most other finishes and lose effectiveness when the boat is stored out of water.<br /><br />Best Use: Performance powerboats and racing sailboats that prioritize slickness or when cost is a primary consideration. Avoid when you don't want paint to build up from annual paint jobs.<br /><br />Anti-Slime Paints<br /><br />During recent years, companies such as Akzo Nobel or Ciba Specialty Chemicals have developed technology that improves the slime-blocking capabilities of bottom paint, e.g. by reducing the growth of sliming organisms, which are impervious to copper. Paint manufacturers have incorporated them into their products, expanding their usability and effectiveness.<br /><br />How do anti-slime paints work? Oversimplified, it's sunblock for your boat's bottom. Most boosting biocides work by preventing photosynthesis in the slime and algae that attaches to the boat. If the slime and algae cannot change sunlight into food they die or more likely they move on to another place that is more to their liking.<br /><br />Ciba's low toxicity additive is called Irgarol, Interlux (which is part of Akzo Nobel) calls their slime-blocking technology Biolux¨. According to Ciba, Irgarol dissipates rapidly, breaks down in water and is fairly low in toxicity to fish, shellfish, mammals and other marine animals. In addition to reducing algae slime, Irgarol allows the copper bottom paint to do a better job on other organisms. The algae layer can actually reduce the amount of copper present on the surface, thus allowing animals to attach.<br /><br />Interlux explains that Biolux¨ is not an ingredient but an antifouling technology that incorporates organic boosting biocides such as Irgarol or many others (such ZPT or Sea Nine 211) into a special biocide release system. By controlling the release rate of the main biocide (most antifouling paints use cuprous oxide) and the boosting biocide you get longer lasting and more effective antifouling protection. The company says that paints containing Biolux are up to 240 times more effective against slime than products solely based on copper.<br /><br />And there is more good news: the new anti-slime additives may actually increase the life of your antifouling paint. The reason is pretty simple: removing slime growth is one of the reasons that boaters scrub their boat bottoms. When antifouling paint is scrubbed, even with relatively gentle materials like burlap, it inevitably removes some active paint film, and thus reduces the effectiveness of the paint. Since Irgarol and Biolux paint formulations remain cleaner, less scrubbing is required.<br /><br />Freshwater Antifouling<br /><br />Thin-film paints are more common in freshwater venues for seasonal antifouling protection. They offer a super slick Teflon (PTFE) finish to keep growth from attaching to the hull in addition to one or more biocides. <br /><br />Best Use: Freshwater or cold, low-fouling salt water or high performance boats that benefit from the friction-reducing properties of Teflon¨.<br /><br />Aluminum Hulls and Underwater Metals<br /><br />Metal hulls and parts require special primers and paints. West Marine carries a complete line of products for these applications. Please call 1-800-BOATING for more information.<br /><br />Good-bye TBT<br /><br />As of 2003 the use of tin-based paints has been outlawed for boats less than 82 feet in length. TBT (tributylin tin) was very effective but the toxicant remained in the environment and affected non-targeted species. As a result of the ban, West Marine stopped selling tin-based paints and replaced them with products that are differently formulated to protect the bottom of your boat or outdrive. Paint makers continue to research and develop more effective antifouling products that don't have a lasting negative effect on the marine ecosystem.
