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Last year I brought two cannonball up from the seabed. I'd like to have them as ornaments in my garden.

I've had them sitting in fresh water for a year, changing it occasionally. What should I do now to preserve them, as I've heard that the iron content makes them difficult to keep intact?

Hope you can help.

Thanks

Ian
 

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The King Of The Divan
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paint 'em with smooth black hammertite.



ColinM
thats what I did with mine that I got from Falmouth - after keeping them in a bucket of water for a long time (changing it every so often), I gave them a good rub down with a wire brush and used the Hammerite.

One of them is still in mint condition after about 7 or 8 years but one loses a bit once in a while. The bits come off in about 5mm thick chunks but I touch it up again with Hammerite.

However, mine are softies as they don't live outside but have free rein of the house :). So not sure how they would have fared it they had to brave the elements.

Snash
 

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The King Of The Divan
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Just out of interest, did you have trouble bringing them up?
nah - they came out the other end - hurt like hell :teeth: sorry, couldnt resist...:embarassed:

no, dead easy - put the first one I found into a goody bag and then tied a lifting bag on and just put enough air in so they were neutrally bouyant a few inches off the seabed then pushed it along in front of me no problem until I found the next one which I then popped in the bag and carried on, until I got bored and sent them up.

Snash
 

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Why would they need running water if they ve been on the seabed for 00s of years??



For real authenticity you could always just fire them at the French:)
To get the salt out of the iron.

Jibbajabba has summed it up well on SWM:

'Putting it basically the answer was NO. Cast Iron is porous, during its time in the sea it will absorb salt water and rust it through. Leaving it in fresh water preserves it and removes some of the salt. The problem you will have, is that when it is removed from the water and it starts to dry out, salt crystals will form, the ball being totally made of rust, which has no structure will crack or crumble. The best preservation is to keep it in water.'
 

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13.05.2012 QPRmageddon Day
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To get the salt out of the iron.

Jibbajabba has summed it up well on SWM:

'Putting it basically the answer was NO. Cast Iron is porous, during its time in the sea it will absorb salt water and rust it through. Leaving it in fresh water preserves it and removes some of the salt. The problem you will have, is that when it is removed from the water and it starts to dry out, salt crystals will form, the ball being totally made of rust, which has no structure will crack or crumble. The best preservation is to keep it in water.'
Ahhhh thanks
 

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Make mine a Pan-Galactic Gargle Blaster.
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Toilet cistern is supposed to be a good place for such objects, frequent water replacement automatically :D

Has the added benefit of water saving too :thumbsup:
 

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Mark Milburn
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I've just been looking at this trying to find a definitive answer. I found some interesting stuff about preserving iron found on the 'Mary Rose'.

Conserving metal objects from the Mary Rose
The conditions around the Mary Rose prevented or slowed down corrosion of metal objects in many cases. However, once objects were recovered and exposed to oxygen again, corrosion could resume. Conservators wished to prevent this happening. Their aims were threefold:
To stop the corrosion process.
To leave the shape of the object unchanged.
To leave the metallic structure of the object unchanged.
To do this they had to tackle a problem caused by the long immersion of the artefacts in sea water. This was that during this immersion the surface layers of metal objects had absorbed chloride ions from the sea water. This could cause two main problems.
Firstly, any water that condensed on the surface of an object would tend to dissolve these ions and form an electrically-conducting solution that would form the electrolyte for electrochemical corrosion. This, together with oxygen from the air could form the ideal conditions for corrosion. To avoid this problem, objects would have to be stored and displayed in extremely dry air – difficult to achieve in a museum, for example, where visitors are continually breathing out moist air.
Secondly, under some conditions, the chloride ions could react to form hydrochloric acid which would itself corrode the metal.
For both these reasons it was necessary to remove the chloride ions.
Three methods were considered:
1. Washing the objects with water to dissolve the chloride ions out of the surface layer.
2. An electrolytic method in which the artefact is made the cathode (negative electrode). The negative chloride ions would be attracted to the positive electrode and drawn out of the metal.
3. Heating the object in an atmosphere of hydrogen. The chloride ions react with the hydrogen to form hydrogen chloride gas which is then sucked out of the furnace.
Experience suggested that method 1 could take up to five years to remove all the chloride ions. During this time, the object would be immersed in a solution containing chloride ions and would therefore be corroding.
Method 2 would be quicker, but could still take two years. There were two disadvantages. Firstly an electrical connection would have to be made to the object and this might damage it. Secondly, there is a possibility of hydrogen gas being produced at the cathode. If this were too vigorous, it could cause damage to corrosion already present on the cathode. As with method 1, during treatment the object would be immersed in a solution containing chloride ions and would therefore be corroding.
For iron objects, heating with hydrogen to 850 °C was the method actually chosen – even this had to be done for a week. A special furnace had to be built to hold objects as big as cannon. The reaction that is taking place may be represented as
2FeCl3(s) + 3H2(g)  2Fe(s) + 6HCl(g)
For safety reasons, the gas used in the furnace was actually a mixture of hydrogen and nitrogen. It turned out to be cheap and convenient to make this gas mixture by decomposing liquid ammonia using a catalyst:
2NH3(l)  N2(g) + 3H2(g)

So I think that's pretty definitive!
 

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Grape shot

Put mine in the toilet cistern for a year then dried them out and put black fireside Grate polish on them and buffed them up.

Still ok now
 
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