copper kettle turns a gunmetal colour

[kalindi]

I went to the boat on Sunday to check if everything was ok after the recent bad weather and noticed that the copper kettle I have had completely changed colour to a uniform gunmetal apprearance. This surface is qite hard and cannot be washed off. On close inspection an oil burning lamp had also changed colour but only in directly exposed areas but generally of a simmillar experience. Everything else seems ok. The only thing that I could think off was that the batteries had over charged and vented gas into the saloon in sufficient quantities to cause this problem but on examiningthe battery bank everything seemed to be OK. So I hope someone can help me understand what has happened. As you can imagine I am a bit worried about what chemicals I have got circulating in the atmosphere. By the way the boat is reasonably ventilated by leaving vents open and has a small solar powered fan running when the sun shines, we are based in southern france, but it is also damp due to the specially bad weather we have at the moment and some leaks still to be fixed.
Thanks in anticipation of the help

 

[footsoldier]

Posted to bump you back up the list.

(I think your diagnosis is correct, but I want to see it confirmed by someone who knows)

 

[kalindi]

Thanks for pushing the question back up the list. It seems a bit strange that there has been no response as I would have thought if it was due to fumes from overcharging a battery then I would not have been the first to do it. I will put my thinking cap back on

 

[chuzzlewit]

copper gets oxidised to verdigris(copper carbonate??)

which is pale green.All it needs is damp and air- nothing toxic. Try wiping with a little battery acid or vinegar. My school chemistry is a bit rusty.

 

[Hoolie]

or dilute oxalic acid, widely available in France.

 

[ianat182]

Mine, a gift from a friend, has also changed colour. I've got it back to the normal colour but not gleaming, with Cif cream, if it doesn't last I'll try Coca-Cola,which I know cleans copper coins without any friction applied. For your lamp I would suggest the same but afterwards use a spray varnish to keep the shine.Someone suggested that Ladies hair lacquer would do it,but if it is an oil lamp, or near flame, I'd not use that.
As to the cause, I think it is the salt air and damp/coldness this year, last year no oxidization at all.

ianat182

 

[Pasarell]

How long is it since you went to the boat?
Sounds like the surface has oxidised in the way water pipes in houses do making the copper go a dark, matt, brown. If the air is damp and salty there will also be a hint of cupric hydroxychloride there which would, perhaps, give the gunmetal appearance although ultimately it would go green. Normally this only happens when the copper is immersed so a bit surprised unless the boat has sunk!
I don't think it is because of fumes from the batteries but VicS might have something to say about that.
To get rid of the hydroxychloride film use a dilute acid, wiping with a lemon may be the simplest way but 10% hydrochloric would be quicker. Take sensible precautions if using acid - gloves and goggles for hydrochloric, G&T for citric. This will not remove the oxide layer though so you will need to abrade with a cream or scourer for that

 

[kalindi]

Thanks for the replies. I will be back on the boat today and see if I can clean back to the originol colour. I am still a bit puzzled as to why the dramatic change in colour it cerainly is a matt grey without any hint of green and it took place over a couple of weeks since I was last there. Anyway I am more relaxed now as nobody has confirmed my worry that it was due to battery acid fumes.

 

[sarabande]

unless you have cooked your batteries in those two weeks, the only possible gas produced by them will be a little hydrogen - which will be in such small volume, and will disperse (think Godenov, Napier Stocks) very quickly.

Did you have a curry on board last time ? Evaporating vinegar, or loo cleaning chemicals could be a contributing factor.

 

[FistralG]

Tomato ketchup is the best thing for getting copper shiney. The acid from the vinegar and the tomatoes is held in contact with the surface by the gel like consistency (doesn't evaporate or slip off too easily) and can be wiped off after a few minutes to leave a gleaming surface.

 

[Cliveshep]

Bare copper exposed to air/damp etc will as you have found oxidise to brown, grey, black and finally green - you can see that on copper roofs which turn a pleasant green.

Brick acid or patio cleaner will clean it but the problem will only start again and the spray lacquer route is probably the only thing to exclude the air and keep the thing shiny. Of course, using a kettle will burn off the lacquer around the edges and sides.

Being a bit of a Philistine here - but why not hang it on the wall nicely lacquered and buy a stainless steel kettle for everyday use?

Frankly, the only way to keep copper or brass shiny is to employ an out-of-work Public Toilet Attendant to polish such items daily!

 

[SAMYL]

Try Cillit Bang, the TV ad shows it cleaning a copper coin very quickly although I havn't tried it myself yet

 

[oldsaltoz]

Swamp gas will turn copper black, any bad egg smell on board?

 

[footsoldier]

Thanks for pushing the question back up the list. It seems a bit strange that there has been no response as I would have thought if it was due to fumes from overcharging a battery then I would not have been the first to do it.

Since no-one has confirmed your fears, it seems all is OK. When I read your original post it sparked a vague recollection of hearing in the past that the phenomenon was an indicator of a battery problem. I was waiting to see the views of the forum as I have a bit of a phobia about this, having been gassed twice by batteries cooking themselves.