andrewturner
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| posted on 24/10/07 at 06:39 PM |
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Chemical Blackening
Does anyone no a way to blacken steel?
I have tried a product Blackfast it works OK but is expensive. What chemicals are used in the process?
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John Bonnett
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| posted on 24/10/07 at 06:58 PM |
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The method I have used and it works well is to heat the metal to red heat and then fully immerse in oil. Keep under the surface until it cools
sufficiently otherwise, the oil will catch light.
This gives a professional and durable finish and costs nearly nothing.
John
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nasty-bob
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| posted on 24/10/07 at 07:23 PM |
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I was looking into this a while back. Proper (hot) chemi-black oxiding can be pretty dangerous as it requires a wetting of the solution, which if done
incorrectly will errupt. And the solution is at 280 deg F. THIS site looks like a good
explanation.
Cold chemi blacking I understand is a bit naff and so not really worth it.
Worth noting that chemi black oxiding doesn't give any corrosion resistance- the part needs oiling for that.
Home anodizing of aluminium on the other hand....clicky
Hope this is some help.
Cheers
[Edited on 24/10/07 by nasty-bob]
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David Jenkins
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| posted on 24/10/07 at 08:55 PM |
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I do the oil blacking method that John suggested - it's fine for steel parts that don't mind being heated up.
I use a large coffee tin full of used engine oil - string the part on a bit of wire, heat it up until it's really hot (until it's gone
grey, but not glowing hot) then plunge it into the oil. Wait a while, take it out and re-heat it until all oil is burnt off it, then plunge it again.
Repeat until you're happy with the colour. Cheap and cheerful.
The only caution when using used oil is to watch out the first time you use it - there could be petrol in the oil, which will catch fire when the
metal goes in. Do it in the open air, have an extinguisher handy, hold the wire in pliers so your hands are well away, and wear gloves.
Do it at your own risk - you have been warned!
David
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C10CoryM
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| posted on 28/10/07 at 02:14 AM |
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One more warning for safety while oil quenching....... immerse it so no air/gas can get trapped under it. We used to quench some small capped
cylinders and sometimes they would take off with enough speed to hit the 30+ft ceiling
"Our watchword evermore shall be: The Maple Leaf Forever!"
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David Jenkins
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| posted on 28/10/07 at 03:43 PM |
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Forgot to mention - you also get copious amounts of foul-smelling smoke, which is why I recommended that it should be done outdoors!
Cof!
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