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Martian Ind

What is that Bronzey colouring on Doll boilers?

Hi,

Just refitted the sight glass on my doll boiler, it was leaking, as a result there has been some corrosion, revealing the Cu beneath.

Does anybody know what the coating/plating is? I have a electrolysis/brush on plating kit which I use for Nickel & Gold.

If somebody knows what the coating is on these boilers maybe I can brush it on.

Thanks

Martin
Timonade

Martin, it seems like Doll boilers are made of brass. If this is the case, then they are not coated; brass is a alloy of copper and zinc (of course, it is possible to plate brass with nickel). In your case dezincification has probably done its job - water has leeched the zinc out of a certain area of the boiler over the years, leaving copper.

The only way to properly fix this is to cut out the corroded area and braze a new patch into place. This is a fair bit of risky work - you could ruin the whole boiler if not experienced - and in most cases is not worth it, it is easier to make or buy a new part.
Of course you can always clean and cover the corroded area with soft solder. It won't look nice, and it only patches up pinholes, but it'll make the boiler usable for a while. This is called postponing the problem.

Please specify the model you're having problems with so boiler material can be identified.
Martian Ind

Timonade wrote:
Martin, it seems like Doll boilers are made of brass. If this is the case, then they are not coated; brass is a alloy of copper and zinc (of course, it is possible to plate brass with nickel). In your case dezincification has probably done its job - water has leeched the zinc out of a certain area of the boiler over the years, leaving copper.

The only way to properly fix this is to cut out the corroded area and braze a new patch into place. This is a fair bit of risky work - you could ruin the whole boiler if not experienced - and in most cases is not worth it, it is easier to make or buy a new part.
Of course you can always clean and cover the corroded area with soft solder. It won't look nice, and it only patches up pinholes, but it'll make the boiler usable for a while. This is called postponing the problem.

Please specify the model you're having problems with so boiler material can be identified.


Hi Thanks for that, please see attached photos



See what I mean by a nice bronzey colour, probably got so hot its some form of annealing...  
MrDuck

It's chemically blued to make it more attractive but time and flames eat away on the blue (or brown) and the brass shines through.
Your boiler looks to be in good condition.
Dampfzauberer

That's the blueing of the boiler!
Very common on old german engines.
The brass has been chemicaly darkened.
(you can't say blackened, because it is not black)

It is a very specific, plum-ish looking colour.
Sometimes even silversish-grey loking.

The thought behind this was, to have the toy steamer's boiler look like the real thing (which were made of steel)
So you can say they wated the brass to look like steel.
Martian Ind

Dampfzauberer wrote:
That's the blueing of the boiler!
Very common on old german engines.
The brass has been chemicaly darkened.
(you can't say blackened, because it is not black)


Thanks for that so if I wanted to " blue it " again how do I do it, and also the chemically darkened or bronzey/steel finish how is this achieved?

Also thanks the engine is practically new apart from the leaking sight glass causing the discolouration, it even came with the filler/oiler and can? and some spare original gaskets and o rings. Do you know whether these are Doll originals or some other additions, there is also some sort of dipper or oiler which I have not shown.

Thanks again see photo


scorpion2nz

I have  used gun bluing creme  with  trail and error producing marginal  results.which at a distance  is better than brass
Atticman

The funnel and can are correct, originally the can was used for measuring out the meths and water I believe.

Im not sure the oiler is original to the engine.

Incidentally that blueing is excellent, and please dont polish it.

It was I believe a chemical process that seems very hard to replicate.

The messy area around the water guage is tricky to clean we can see what others think to that. Maybe a tiny bit of vinegar would clear it, but it will mess the bluing up  

the glass is often fragile, sometimes a thin smear round the leaky area with silicon sealant can help.
Steam Models

As everyone has already said it's a chemical Bluing which they do for brass.

the Model Engineer members have all given their own and different recipies over the years.
And I'm sure that a search will bring them back.

In the seventies the Japanese Camera makers used a brass blackening on the top and bottom hats of their Cameras.

Most engineering shops also have different chemical recipies as well.
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