jenevers Posted August 18, 2018 Report Share Posted August 18, 2018 Here's an idea. Rust needs water and oxygen, so, how about depriving your bilge of oxygen by filling it with carbon dioxide by using a CO2 extinguisher? Discuss :-) Link to comment Share on other sites More sharing options...
WotEver Posted August 18, 2018 Report Share Posted August 18, 2018 So you’ll have a bilge full of carbonic acid instead? That’s assuming that you’re constantly replenishing the CO2 with a never ending supply of extinguishers of course... Surely better to remove the other component - Water. Link to comment Share on other sites More sharing options...
rusty69 Posted August 18, 2018 Report Share Posted August 18, 2018 That was a short discussion! 2 Link to comment Share on other sites More sharing options...
jenevers Posted August 18, 2018 Author Report Share Posted August 18, 2018 2 hours ago, WotEver said: So you’ll have a bilge full of carbonic acid instead? That’s assuming that you’re constantly replenishing the CO2 with a never ending supply of extinguishers of course... Surely better to remove the other component - Water. How is carbonic acid created? What's that acid in Vactan? Link to comment Share on other sites More sharing options...
Ian F B Posted August 18, 2018 Report Share Posted August 18, 2018 I think it's phosphoric acid, I use Vactan,seems to work well with good preparation and dries quickly so can be overcoated with primer or holding cost within an hour of so,? Link to comment Share on other sites More sharing options...
Neil2 Posted August 18, 2018 Report Share Posted August 18, 2018 Seriously folks... I have often wondered about the wisdom of venting bilges, though it is accepted wisdom that creating some air flow through the bilge is a good idea, it also introduces fresh oxygen and if the air flow doesn't dispel what moisture is in the bilge might it actually make matters worse? There's surely a case for sealing up the bilge entirely so once the oxygen has been used up (in the rusting process) no more can form. Link to comment Share on other sites More sharing options...
Steilsteven Posted August 18, 2018 Report Share Posted August 18, 2018 11 minutes ago, Neil2 said: Seriously folks... I have often wondered about the wisdom of venting bilges, though it is accepted wisdom that creating some air flow through the bilge is a good idea, it also introduces fresh oxygen and if the air flow doesn't dispel what moisture is in the bilge might it actually make matters worse? There's surely a case for sealing up the bilge entirely so once the oxygen has been used up (in the rusting process) no more can form. Or you could seal the bilge by treating and painting it, that would keep the oxygen at bay. Keith 1 Link to comment Share on other sites More sharing options...
larryjc Posted August 18, 2018 Report Share Posted August 18, 2018 Or do what I do and keep it dry!! Link to comment Share on other sites More sharing options...
Ray T Posted August 18, 2018 Report Share Posted August 18, 2018 2 hours ago, larryjc said: Or do what I do and keep it dry!! Some you can't keep dry. Our boat, Reeves hull, has a deep cratch. From the two side lockers pipes run the length of the boat to the engine room bilge. Although we have a cratch cover some water gets in, depends upon wind force and direction. This drains through to to the engine room bilge. Also when we drain the boat down for winter the calorifier also vents into the bilge, as it does on the odd occassion when the PRV blows. There is a separate sump beneath the engine, I can keep this dry. Link to comment Share on other sites More sharing options...
larryjc Posted August 18, 2018 Report Share Posted August 18, 2018 I guess I'm lucky with a pram over the hatch and only the stern gland to worry about. However, previous owners weren't so careful and there has clearly been quite a lot of water in there in the past. Which I why I have some fertran, bilge paint, wire brushes etc all ready for me to make the effort to paint it all out as soon as I can find the motivation!!! Link to comment Share on other sites More sharing options...
blackrose Posted August 19, 2018 Report Share Posted August 19, 2018 15 hours ago, jenevers said: How is carbonic acid created? Water + CO2 Link to comment Share on other sites More sharing options...
blackrose Posted August 19, 2018 Report Share Posted August 19, 2018 18 hours ago, jenevers said: Here's an idea. Rust needs water and oxygen, so, how about depriving your bilge of oxygen by filling it with carbon dioxide by using a CO2 extinguisher? Discuss ? Unless you have gas tight bilges you'd have to keep filling until you filled the whole cabin with CO2 and it was coming out of the vents. By that stage you'd already be dead. Link to comment Share on other sites More sharing options...
MtB Posted August 19, 2018 Report Share Posted August 19, 2018 (edited) 19 hours ago, Steilsteven said: Or you could seal the bilge by treating and painting it, that would keep the oxygen at bay. Keith Which is almost my thinking too. If painting seals out the oxygen, why does groupthink say is there a need to ‘treat’ the rust first with vactan or similar? Surely once painted the oxygen is sealed out, so further rusting is prevented whether or not existing rust has been ‘converted’ or ‘treated’. I suspect it is simply because it sounds intuitively the right thing to do, so a whole industry has sprung up selling rust converters to a willing but misinformed market. Edited August 19, 2018 by Mike the Boilerman Link to comment Share on other sites More sharing options...
Murflynn Posted August 19, 2018 Report Share Posted August 19, 2018 (edited) 19 hours ago, Neil2 said: Seriously folks... ............................ it also introduces fresh oxygen and if the air flow doesn't dispel what moisture is in the bilge might it actually make matters worse? There's surely a case for sealing up the bilge entirely so once the oxygen has been used up (in the rusting process) no more can form. ahh .... the dreaded fresh oxygen. dangerous stuff that - much better to have old and stale oxygen. .............................. err, ..................... but ....................... how do you get fresh oxygen without air flow? anyway, millenia of boat building experience has established that all spaces should be well ventilated - some narrowboat builders seem to have no knowledge of proper boatbuilding. Edited August 19, 2018 by Murflynn Link to comment Share on other sites More sharing options...
Tony Brooks Posted August 19, 2018 Report Share Posted August 19, 2018 1 hour ago, Mike the Boilerman said: Which is almost my thinking too. If painting seals out the oxygen, why does groupthink say is there a need to ‘treat’ the rust first with vactan or similar? Surely once painted the oxygen is sealed out, so further rusting is prevented whether or not existing rust has been ‘converted’ or ‘treated’. I suspect it is simply because it sounds intuitively the right thing to do, so a whole industry has sprung up selling rust converters to a willing but misinformed market. If paint is permeable to water you can bet its also permeable to gasses like oxygen. The fact paint can micro-blister when water is trapped on the surface shows it is water permeable. I suspect the rust treatment is supposed to form a less permeable surface to be better at keeping oxygen away from the steel underneath. I think International recommended (or did recommend) a minimum of five coats of Danbolin bilge paint. Not sure ow permeable two pack is or water based paint. Maybe the duck keeper has some info on this. Link to comment Share on other sites More sharing options...
PeterF Posted August 19, 2018 Report Share Posted August 19, 2018 On 18/08/2018 at 11:34, jenevers said: How is carbonic acid created? By dissolving carbon dioxide in water. Carbon dioxide in an enclosed space (such as a boat cabin) is dangerous as it is an asphixiant. Link to comment Share on other sites More sharing options...
Captain Pegg Posted August 19, 2018 Report Share Posted August 19, 2018 4 hours ago, Tony Brooks said: If paint is permeable to water you can bet its also permeable to gasses like oxygen. The fact paint can micro-blister when water is trapped on the surface shows it is water permeable. I suspect the rust treatment is supposed to form a less permeable surface to be better at keeping oxygen away from the steel underneath. I think International recommended (or did recommend) a minimum of five coats of Danbolin bilge paint. Not sure ow permeable two pack is or water based paint. Maybe the duck keeper has some info on this. It seems more logical to me that blistering occurs because the paint is impermeable, otherwise wouldn't whatever causes the blister be able to escape from under the paint? The benefit of rust treatment is to provide a uniform surface to which paint will adhere. It shouldn't affect permeability of the finished paint system but it should help it to stay stuck to the boat. Rusted metal will have small voids within it because of the way rust forms and these will remain under the applied paint and potentially cause the system to fail. Best to treat rust by mechanical removal rather than by chemically converting if possible. Reality is that both are often necessary. Let's see if Dr Duck concurs with either of our premises. JP Link to comment Share on other sites More sharing options...
WotEver Posted August 19, 2018 Report Share Posted August 19, 2018 10 hours ago, blackrose said: Water + CO2 H2O + CO2 = H2CO3 Link to comment Share on other sites More sharing options...
Tony Brooks Posted August 21, 2018 Report Share Posted August 21, 2018 On 19/08/2018 at 13:29, Captain Pegg said: It seems more logical to me that blistering occurs because the paint is impermeable, otherwise wouldn't whatever causes the blister be able to escape from under the paint? The benefit of rust treatment is to provide a uniform surface to which paint will adhere. It shouldn't affect permeability of the finished paint system but it should help it to stay stuck to the boat. Rusted metal will have small voids within it because of the way rust forms and these will remain under the applied paint and potentially cause the system to fail. Best to treat rust by mechanical removal rather than by chemically converting if possible. Reality is that both are often necessary. Let's see if Dr Duck concurs with either of our premises. JP Some years ago we had a bad winter where snow stayed on boats for many weeks and enough boats to cause notice had micro-blistered. Craftmaster paints got involved and we discussed in on this forum. Eventually Phill Speight concluded that the water sitting on the paint, under the snow, had permeated the paint film causing the micro-blisters. We also have a number of people periodically agreeing with the notion that you should not have things like mats laying on the paint because it causes paint breakdown and rust. If paint was not permeable then how do you account for the above. Link to comment Share on other sites More sharing options...
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