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Post by yorkshireman on Mar 1, 2008 8:21:06 GMT
How do I do the blackening of a steel part with both silver-solder and soft solder joints? I am looking for a uniform black color. Thanks Johannes
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Post by Tel on Mar 1, 2008 8:24:13 GMT
I've had great success with oil blackening, but it ain't gonna take on any species of solder Don't know of much that will, other than paint.
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Post by gilesengineer on Mar 1, 2008 11:35:16 GMT
I do recall in the model railway world they use chemical blacking. I think the manufacturer may have been Carr's.
Good luck
Giles
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Post by ron on Mar 3, 2008 11:26:54 GMT
Frost Restorations [www.frost.co.uk] do a metal blacking kit which does not require heating or quenching, only snag is you would need to be using it a lot as the price is £35. Ron
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steam4ian
Elder Statesman
One good turn deserves another
Posts: 2,069
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Post by steam4ian on Mar 3, 2008 12:12:13 GMT
G'day Johannes. Gile's response reminded me that lead lighters use some kind of blackening for the lead tracing after they have soldered it up; it gets rid of the bright spots. May be worth a try. You do have lead light in England. regards, Ian
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Noddy
Statesman
Posts: 672
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Post by Noddy on Mar 3, 2008 14:05:32 GMT
Your danger with solders and brazes comes if you use alkalis which will attack tin, cadmium zinc and possibly copper components of the solders.
With soft solder you cannot use much heat either.
The traditional "Bluing" which is used on soft soldered double barrel guns consists of inducing the part to rust evenly in moist (but not condensing) air, boiling it and rubbing it down gently with degreased steel wool, then repeating and repeating...... until it looks black enough.
There are all sorts of witches brews for inducing the rust, most needlessly contain nasties like mercuric chloride. Ignore them!, they're bullshit.
The important thing is to have the work piece and anything which comes into contact with it totally de greased.
a quick waft of the work over a bottle of conc Hydrochloric acid will have it rusting merrily.
Instant Bluing, is probably best achieved by giving your degreased work a very thin copper plating (dip it in copper sulphate that has been acidified with a little extra dilute sulphuric acid for a couple of minutes)
then expose it to hydrogen sulphide, which gives the copper plating a coating of black copper sulphide.
For the hydrogen sulphide, you could see if those little bottle shaped stink bombs are still available (ammonium sulphide) or generate your own with virtually any sulphide in dilute hydrochloric acid. Asking the local secondary school or college might be a good way to get the Hydrogen sulphide.
If you do it yourself, keep the work and the rotten egg smell in a sealed plastic bag, well out of doors, hydrogen sulphide is poisonous and smell is no guide to it's concentration, as it paralyses your sense of smell.
Hope this helps
Keith
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Post by AndrewP on Mar 3, 2008 15:21:21 GMT
Used pickle will copper plate an item if you introduce something ferrous into it. Hardboiled eggs can give you the sulphide required.
Might just have both to hand.
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Noddy
Statesman
Posts: 672
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Post by Noddy on Mar 3, 2008 17:29:35 GMT
Hydrogen Sulphide: There's a thought, Harrogate is coming up isn't it...
"....Would you like to see the sulphur well darling......"
Keith
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Post by petercolman on Mar 3, 2008 21:14:59 GMT
The shotgun barrel makers use a saturated solution of caustic soda with an oxidising agent - sodium chlorate or similar and boil the degreased components in this and deal with the solder joints with printers ink applied afterwards. If you go for this method, beware boiling caustic is very nasty, the fumes make you giddy anf the sollution with take your skin off in moments, this is not for the faint hearted, if you need more help contact me, I used this process at home for some years to treat gun barrels Peter
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Post by yorkshireman on Mar 4, 2008 0:12:36 GMT
Many suggestions, Noddy's Chemistry idea is attractive. As a retired Chemical Engineer the approach to - first deposit a uniform layer of Copper on the part and in - second step colorize the Copper into black CuS using H2S sounds good to me.
Maybe I'll do it like this: IronSulfide (FeS) ist used in Labs to create small amounts of H2S gas. One can buy FeS in science shops, or on ebay at this very moment.
The part will be plated in a CuSO4 solution, hanging on a bit of plastic string. Once the part is uniformally covered with Copper, take it from the solution, rinse it with Water, not touching it. Then one might hang it into another empty container, that can be closed, airtight. On the bottom of that vessel is a jar with a small amount of FeS. Pour a bit of acid over the FeS, close the lid and wait.
FeS plus any acid will create H2S. The fresh Cu-layer should go black quickly.
H2S is not only smelly, it is a Very Poisonous Gas! I did work in places, where H2S could be an instant killer. One sniff of H2S in a high concentration and one is dead before one hits the ground!
The questions are: Is the effort really worth it? Is the Copper-layer (fresh or blackend) really stable enough?
Or is the initial suggestion to just spray the part with some black paint the reasonable way to do it?
I'll find out and report here. Johannes
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