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Author: Subject: Metal surface treatments
mactuan12
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[*] posted on 12-1-2020 at 23:38
Metal surface treatments


This thread is intended to be about decorative and/or functional chemical surface treatments for metals, preferably using OTC chemicals. Please add your experiences.

Here's one I played with recently, to highlight some text etched into a copper plaque. Its based on the formulas I found here
Black Copper Patina

A solution of potassium sulphide applied to bare copper produces a black patina of copper sulphide. Not possessing any potassium sulphide I mixed saturated calcium sulphide solution ("Lime Sulphur" from a garden shop) with saturated potassium sulphate solution ("Sulphate of Potash" from a garden shop).
The quantities were very roughly equal (not good science, but then all I wanted was to blacken some copper :D). The resulting solution instantly produced a thick black non-adherent layer on clean copper. Diluting to 5% with water worked much better, the reaction was slower (blackening over 2-3 seconds) and producing a thin matt black coat with excellent adhesion. Polishing with fine steel wool to highlight the etching left the blackened areas shiny grey (like graphite), giving a lovely 'antique' effect.
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BromicAcid
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[*] posted on 13-1-2020 at 03:49


I did some electroplating of copper on a sign at one point and treated it with 'liver of sulfur' made by dissolving some sulfur in a potassium hydroxide solution. Worked well, just wiped it on and washed it off giving a deep deep orange/red almost black coloration.




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Armus_
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[*] posted on 14-1-2020 at 09:50


im not sure if it works but i have seen it happen before.

so there is a way to show the crystal structure of iron (not steel) by putting iron in a solution of copper chloride (slightly acidic) and when you see the crystal structure then take it out, rince it off, and dip it in a hot oil solution

correct me if im wrong, im wanting to do this experiment but i never got the chance to do so




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