larryjc Posted October 10, 2017 Report Share Posted October 10, 2017 I know this has been discussed earlier this year but I have a slightly different question and didn't want to tag onto the end of an old thread. My water tank needs repainting - I think. I have a large hinged cover so can see inside easily and there are rust streaks and it looks quite manky. Mind you the water tastes fine. I don't want the hassle of stripping back to bare metal and using an epoxy because despite the large cover, my foredeck is tiny and access will be a B***ch. As I understand it until EU rules changed, a bitumen paint was classed as OK. One product - Rylard - states that its still Ok to use on tanks that have already had a bitumen paint applied. I've also spoken to International Yach paints who have 'Intertuf 016' and they say the same thing. Quote one chandlery - 'its easy to apply with a roller - clear off the loose paint/ rust and slap a coat or two over the top.' Does anyone have experience of these products? Link to comment Share on other sites More sharing options...
Neil2 Posted October 10, 2017 Report Share Posted October 10, 2017 I don't think there's much difference between any of the bitumen based products. I don't know the details as to why some of them have been described as unsafe to use on potable water tanks but if it's because of the bitumen base, which it presumably is, that makes them all "unsafe". The problem is if you have a bitumen coated tank you will have to remove every trace of it before you can use anything else. I suspect in the vast majority of integral tanks that is a practical impossibility. I still tend to think that once the bitumen has hardened the risk to health must be tiny, but I wouldn't drink the water from my integral tank anyway. (Actually I wouldn't drink the water from any storage tank.) I'd be more concerned about the possibility of the rust taking hold and perforating the hull from the inside so I would stick with the blacking and IMHO any old black will do. Link to comment Share on other sites More sharing options...
bizzard Posted October 10, 2017 Report Share Posted October 10, 2017 (edited) Bitumen is anticeptic, thats why swans and ducks pecking at a bitumen painted hull don't get ill with food poisoning. Childrens playgrounds are bitumen covered for when children fall over and graze their knees they're usually not infected. In days of yore and gore on navy sailing ships, amputated limbs after being sawn off, the bloody stumps left over were bunged up with hot tar to seal it and stop infection. Aneasthetic was half pint of rum and a bonk on the head with a mallet. Most died of shock with this treatment though. Bitumen is good for you. Edited October 10, 2017 by bizzard 1 Link to comment Share on other sites More sharing options...
Tony Brooks Posted October 10, 2017 Report Share Posted October 10, 2017 If there is time and the ambient temperature is OK maybe treat the cleaned off rust patches with something like Vatan/Fertan before re-blacking. Link to comment Share on other sites More sharing options...
larryjc Posted October 10, 2017 Author Report Share Posted October 10, 2017 (edited) Actually I think blacking bitumen and bitumen paint are different things but that said I think I'll stick with it. I always drink from these tanks in the UK. When I was abroad that was another matter. A few Aquatabs don't do any harm though. I gess as ex RN for 30 years (but not from the time of half a pint of rum and a bonk on the head) my digestive system is reasonably tough. Edited October 10, 2017 by larryjc spalling mastike Link to comment Share on other sites More sharing options...
Tony Brooks Posted October 10, 2017 Report Share Posted October 10, 2017 Yes, my shorthand for re-coating with a suitable bitumen based product. Link to comment Share on other sites More sharing options...
alan_fincher Posted October 10, 2017 Report Share Posted October 10, 2017 I think that unless you can remove all visible rust, and ideally also treat it, you will find that just slapping on new bitumen doesn't last that long. My evidence for this is that on our last boat I paid quite a lot of money to the local marina engineer to prepare and paint the tank, but within no more than a couple of years rusty water came out the taps as soon as it got anywhere close to empty. I then spent a lot of unpleasant days myself stripping and de-rusting it, "Vactan-ing" it, and blacking it, and some 7 years later the water quality still seemed pretty good. IMO it's not a winter job, though, as the products involved will not "go off" properly - it really needs to be a summer job. Link to comment Share on other sites More sharing options...
larryjc Posted October 10, 2017 Author Report Share Posted October 10, 2017 I get that but there's rust there now yet I don't get any coming through - maybe because I never let it get more than half empty. Of course this begs the question as to whether I need to do it at all!! If I do do it over the winter I'll use a hot air gun to dry it and once painted can afford to leave it empty for weeks even a few months to cure. Link to comment Share on other sites More sharing options...
Dr Bob Posted October 10, 2017 Report Share Posted October 10, 2017 4 minutes ago, alan_fincher said: IMO it's not a winter job, though, as the products involved will not "go off" properly - it really needs to be a summer job. I would avoid any painting job if the temperature is below 15 deg C, particularly if it is important to get a good cure ..ie in water tank. 2 pack systems need to chemically react and those reactions take place too slowly below 15C and one pack systems rely on evaporation of solvents and then air/moisture curing which again is slow below 15C. A further issue though is water condensation on the surface and you should always try and be 3 deg C above the dew point, which is not easy when you start dropping down in temperatures. There are systems that cure below 15C, ie some epoxies etc but in the main this will be a compromise so best to leave it until you can get some heat onto the curing system. Link to comment Share on other sites More sharing options...
larryjc Posted October 10, 2017 Author Report Share Posted October 10, 2017 The Rylard spec sheet quotes curing times down to 10 degrees but I take your point about condensation. Oh well, another job I can put off until next year. Link to comment Share on other sites More sharing options...
alan_fincher Posted October 10, 2017 Report Share Posted October 10, 2017 13 minutes ago, larryjc said: The Rylard spec sheet quotes curing times down to 10 degrees but I take your point about condensation. Oh well, another job I can put off until next year. If part of an integral tank is below water line, it is doubtful that water will be as much as 10 degrees, so the side of the tank will not be either. We currently have some hull lining down in Flamingo, our ex working boat, and my wife decided to remove loose rust and treat the riveted sides last week. She applied Kurust, which quickly cured above the water line, but stayed un-cured below it. Fortunately a fan heater did eventually persuade it, but it wasn't even cold that day. 1 Link to comment Share on other sites More sharing options...
IDS Posted October 10, 2017 Report Share Posted October 10, 2017 Wait for next summer. In the mean time look for a bitumen coating with WRAS approval for potable water tanks. This is the only guide to suitability. Expect the product to be more expensive as producers have to pay for the approval process. (the product may be identical with unapproved products, but you don't know) Vactan used to claim it was suitable for water tanks, not so sure about fertan, I used vactan as a bare metal treatment on rusty bits Link to comment Share on other sites More sharing options...
larryjc Posted October 10, 2017 Author Report Share Posted October 10, 2017 As I understand it no bitumen coatings are now approved for new tanks but can some can be used on ones that already have used it. A quote from the Rylard web site: Legislation has resulted in the withdrawal of the Water Research Council’s approval of bitumen for use in water tanks and equipment for all public services. This means that bituminous solutions are no longer approved by the WRC, but their continuing use on existing bituminised tanks is permitted under BS3416 on boats. If your boat has a water tank already coated with bitumen, you can use Water Tank Coating to maintain it. New water tanks must use two pack bitumen-free coatings (such as Epicol SF). Link to comment Share on other sites More sharing options...
ditchcrawler Posted October 10, 2017 Report Share Posted October 10, 2017 2 hours ago, bizzard said: Bitumen is anticeptic, thats why swans and ducks pecking at a bitumen painted hull don't get ill with food poisoning. Childrens playgrounds are bitumen covered for when children fall over and graze their knees they're usually not infected. In days of yore and gore on navy sailing ships, amputated limbs after being sawn off, the bloody stumps left over were bunged up with hot tar to seal it and stop infection. Aneasthetic was half pint of rum and a bonk on the head with a mallet. Most died of shock with this treatment though. Bitumen is good for you. When I was an apprentice boy we use to use the old style electrical insulating tape on cuts, that was cotton impregnated with some sort of black pitch Link to comment Share on other sites More sharing options...
WotEver Posted October 10, 2017 Report Share Posted October 10, 2017 23 minutes ago, ditchcrawler said: When I was an apprentice boy we use to use the old style electrical insulating tape on cuts, that was cotton impregnated with some sort of black pitch And then you’d spend the next three weeks trying to get your fingers clean. I came across an old roll of that insulation tape a few months back when having a clear out. Link to comment Share on other sites More sharing options...
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