Gas Bottle Anode??

DJE

DJE

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As my gas locker is under the cockpit seats it catches rainwater and the occasional dollop of sea water. All this passes out through the drain but the bottle tends to go rusty and leave a stain on the transom where the drain comes out. Now I've got these lumps of zinc in the garage (old anodes) so if I cut a bit off and fix it to the gas bottle will this reduce the rusting? I'm thinking of attaching it to the base ring of the bottle rather than the pressure vessel itself but obviously I don't want to risk any damage to the bottle. I've got a similar problem with the spare bottle which lives in the anchor locker. Good idea or not?
 
Problem is that for an anode to work it and the item being protected need to be immersed in water, or at least connected by a continuous film of it. What you are experiencing is general corrosion caused by splashes, discontinuous films, condensation, etc. So an anode might work on steel immediately surrounding it but is unlikely to have much effect further away.

My solution is to cut shallow trays from polythene bottles a little bigger than the gas bottles. A hole can be drilled in them to let surplus water out. These won't stop all the rusting but at least the stains won't be on the boat.
 
The zinc would have to be attached to the base of the bottle in such a way that there was a good electical connecton between the two., ie firmly bolted to bare metal.
It might work if the base of the cylinder and the zinc were immersed in water but probably won't if its not.

Try it by all means but I am not at all optimistic that it will do much good.

Although there is no requirement for the gas bottle locker to be sealed above the level of the high pressure components I think the more sensible thing would be to fit a close fitting lid that will not allow water into the locker. A lid with a good seal would be even better but the locker would then have to be provided with a vent.
 
By all means try, but I suspect that it won't make a lot difference to overall surface rusting of the bottle. I would look at trying to stop water getting into the gas locker in the first place. As for the spare, what about a stout (plastic ?) wrapper of some type, but you won't want it to retain water though.
 
Not quite sure of why its a problem really ?
Surely you change the bottles often ... possibly nit.
We use 2 907 camping gaz bottles for liveaboard use, each bottle lasts around a month, then is simply exchanged.

Do you refill the ones you have ?.

Joe n Jayne
 
I've done my research now and I see the problem, at least if you just have the orginal Sadler 29 gas bottle stowage. Not a locker at all just an open fronted compartment in the cockpit next to a cockpit drain.

The ideal solution to that would be a fixed and gas tight front to the space and a weather proof top. I dont know how you'd make the top weatherproof though. If the front is completely sealed the compartment would need its own drain so perhaps a drain into the cockpit would suffice, although not complying with the requirements of the Boat Safety Scheme. (I am right in thinking that the cockpit drains exit via the transom well above the water line? ) Also if the top were completely sealed it would be necessary fit a separate vent.

The space is only designed for a 907 Gaz cylinder, I think, so that rules out Rickp's suggestion to use the plastic BP gas bottles!
 
Have had same problem, after much thought stuck bottle in a bin liner trimmed to lenght sand taped around the top leaving the fill/discharge valve in the air. solved it for me. /forums/images/graemlins/grin.gif
 
Vic,

There has been a good deal of correspondence on this subject on the Sadler site. I think the 29 is very similar to my 34 so far as gas is concerned. The intention is that any gas that escapes from the installation drains out of the cockpit drains through the transom, above the water line. Sounds OK, except that with a reverse sheer transom the skin fittings slope downwards, creating a 'U-bend' for drain water to gather in and preventing any gas from getting out.

The last boats built had an additional drain in the gas locker, this drops straight down to the hull and exits there. Unfortunately, to retrofit this is quite a big job as the hull is double-skinned with foam between. There have been suggestions that a modified Eberspacher exhaust fitting let into the transom would overcome the problem, as it is designed to slope downwards even in a reverse sheer transom.

The gas locker is designed for two Gaz cylinders, although it is possible to fit one Gaz plus one Calor. I don't find rusting to be a big problem: some of the exchange bottles we pick up in Greece are very badly corroded anyway, so a plastic tray is needed before they even get wet!

Vyv
 
zincs would only work in a limited area round the zinc and maybe doubtful even then. the paint on camping gaz cylinders is cr*p.

simple solution - spray each cylinder with duck oil or paint over with waxoyl. when exchanging a quick wipe with a petrol soaked rag will remove the wax. messy but much more likely to work than zinc.

oxalic acid will remove the rust stains
 
Thanks everybody for your ideas and advice.
I've modified the gas locker by cutting the original door about and inch below the level of the cockpit seats and glassing the lower portion permanently in place. Before doing this I installed a new drain from the bottom of the locker to the transom (using tapered washers to keep the skin fitting horizontal) but the lid is still far from weathertight. Perhaps the next job is to look at some sort of foam seal to the locker lid. The spare bottle in the anchor locker is already in a stout platic bag which reduces the rusting a little.
I can't see what the plastic trays under the bottle would achieve, surely they'd fill up with water and overflow via the drain.
 
<<< I can't see what the plastic trays under the bottle would achieve, surely they'd fill up with water and overflow via the drain. >>>

If you'd like to read my post again, I said to drill drain holes in the trays. If the bottles are going to rust, which they will if left alone for a while, then let them rust somewhere other than on the floor of the locker.
 
Vyv , thanks for a bit more info about the Sadler 29. What I know is a bit dated (1981)

The pictures I have show a space for only one gas bottle. I thought it was a Gaz one but the text implies that there is room for a Calor one.

I agree with DJE about the plastic trays. He is complaining about rust stains on the transom where his retrofitted gas bottle locker drain exits not in the locket itself although I am sure he'd like to keep that clean and stain free as well.

I feel the only satisfactory answer is to weather proof the top cover. It'll need some sealing strip and some means of clamping the cover down tight on the seal. Thats the bit that will be difficult.

In the meantime a periodic clean with oxalic acid or an oxalic acid based cleaner such as Y10 perhaps.
 
My mistake on the staining location, should have re-read the OP. I get rust stains all over the floor of the locker.

I don't know the 29 well but I know there are lots of similarities between it and the 34. So not certain whether the 29 carries 1 or 2 bottles. I agree on the oxalic based cleaner. I use Boatlife, it shifts rust stains instantly.
 
Re: Gas Bottle Anode?? / Sadler29

VicS and Vyv,

Just for interest can confirm that the Sadler29 'locker' (hinged lid) will ONLY accept one 907 type GAZ . In view of the ridiculous cost of GAZ I carry one or two 7Kg Calors strapped securely against the transom. I find this no inconvenience at all. and it makes switching off at the cylinder very convenient.

I do carry a 907 in the original locker as an emergency supply and for exchange if necessary abroad. My solution to the rusting is to spray a 'new' cylinder with WD40 and encase it in a strong sealed plastic bag until needed. Strange that the (galvanized) Calor bottles never rust /forums/images/graemlins/grin.gif

Vic
 
Surely an anode is not going to stop rusting anyway? Different process to electrolysis ..?

My vote would go with the Waxoyl solution // simple and doesn't involve surgery:-)

Roll on Summer !

All best Nick (see you in the yard)
 
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