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--part1_15e.8863502.29967cad_boundary Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Most of the following is in the archives. First Paint Stripping Don't sand blast a tank ever. Sand blasting will remove all the anodize from aluminum and the galvanize from steel tanks. Use a chemical stripper with methylene chloride - zip strip or other type of stripper that you can get in a hardware store. Always use them in with good ventilation. Do not use the new past on strippers. These are the ones that use a paper backing. They use sodium hydroxide. Sodium Hydroxide etches aluminum. Clean After the paint is off use a good cleaner and some red scotchbright to clean the surface of all oxides. Do not rub hard, all you want to do is get the powdery stuff off. Rinse well. Primer The best primer for any tank is a chromated epoxy aircraft primer. These are qualified to a number of military specs. The most common are: TT-P-1757 (Zinc Chromate) Mil-P-23377 (solvent born Strontium Chromate) Mil-P-85582 (water based version of 23377) Check with companies that repaint aircraft, they may sell you a kit. If you can't get one of these, and you may not be able, go to a good autobody supply store and get just about any good epoxy primer for aluminum & steel. Top Coat (paint) Epoxy is a great primer but is attacked by UV so you have to put a top coat on it. The best are polyurethane based. Again get this at the autobody supply store. DuPont Imron is good but ask around. Most of the topcoats I use are mil-spec. The most popular is Mil-C-85285 which is formulated to Navy requirements. Baking after paint Don't At temps above 250 F aluminum will go through a transformation which is not reversible. What happens is the crystal structure changes and it will get brittle. This is when you hear about tanks blowing up. Never Bake any high pressure cylinder If you are worried about what your tanks look like - buy bare galvanized or anodized only and rinse them well after each dive. Pete Johnson Sikorsky Aircraft Materials & Processing --part1_15e.8863502.29967cad_boundary Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: 7bit <HTML><FONT FACE=arial,helvetica><FONT SIZE=2>Most of the following is in the archives. <BR> <BR>First Paint Stripping <BR> <BR>Don't sand blast a tank ever. Sand blasting will remove all the anodize from aluminum and the galvanize from steel tanks. Use a chemical stripper with methylene chloride - zip strip or other type of stripper that you can get in a hardware store. Always use them in with good ventilation. <BR> <BR>Do not use the new past on strippers. These are the ones that use a paper backing. They use sodium hydroxide. Sodium Hydroxide etches aluminum. <BR> <BR>Clean <BR> <BR>After the paint is off use a good cleaner and some red scotchbright to clean the surface of all oxides. Do not rub hard, all you want to do is get the powdery stuff off. Rinse well. <BR> <BR>Primer <BR> <BR>The best primer for any tank is a chromated epoxy aircraft primer. These are qualified to a number of military specs. The most common are: <BR> <BR>TT-P-1757 (Zinc Chromate) <BR>Mil-P-23377 (solvent born Strontium Chromate) <BR>Mil-P-85582 (water based version of 23377) <BR> <BR>Check with companies that repaint aircraft, they may sell you a kit. If you can't get one of these, and you may not be able, go to a good autobody supply store and get just about any good epoxy primer for aluminum & steel. <BR> <BR>Top Coat (paint) <BR> <BR>Epoxy is a great primer but is attacked by UV so you have to put a top coat on it. The best are polyurethane based. Again get this at the autobody supply store. DuPont Imron is good but ask around. <BR> <BR>Most of the topcoats I use are mil-spec. The most popular is Mil-C-85285 which is formulated to Navy requirements. <BR> <BR>Baking after paint <BR> <BR>Don't <BR> <BR>At temps above 250 F aluminum will go through a transformation which is not reversible. What happens is the crystal structure changes and it will get brittle. This is when you hear about tanks blowing up. <BR> <BR>Never Bake any high pressure cylinder <BR> <BR>If you are worried about what your tanks look like - buy bare galvanized or anodized only and rinse them well after each dive. <BR> <BR>Pete Johnson <BR>Sikorsky Aircraft <BR>Materials & Processing</FONT></HTML> --part1_15e.8863502.29967cad_boundary-- -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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