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Topic: Coloring Steel chemically.  (Read 4086 times)

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Offline Sarhil

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Coloring Steel chemically.
« on: July 09, 2018, 04:17:24 AM »
Hello,
I am a computational mechanics scientist which has a weak background in chemistry.
I have a problem which I ask kindly to help with.
I have different kinds of concrete with very tiny steel fibers.
I make cross-sections of some spicements and I want to  detect these fibers using some automated software I developed, which depends on colors canals.
The problem is the color of the steel is not unique and I want to color the steel chemically to red, blue or green. Is it possible?
Sorry if I have some language mistakes but I am German.


Thank you.
Vielen Dank.


Offline Enthalpy

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Re: Coloring Steel chemically.
« Reply #1 on: July 09, 2018, 11:03:21 AM »
Maybe a bath that makes the steel black or dark. It's used for black screws and other mechanical parts
https://de.wikipedia.org/wiki/Br%C3%BCnieren
with a bit of luck, the bath won't blacken the concrete.

Offline Sarhil

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Re: Coloring Steel chemically.
« Reply #2 on: July 11, 2018, 10:34:17 AM »
Thank you for this idea,

I will try it but the problem which I could have later, I have black stones inside the concrete and in general my concrete is darker than the usual concrete (ultra high performance concrete).
 

Offline Arkcon

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Re: Coloring Steel chemically.
« Reply #3 on: July 11, 2018, 10:52:52 AM »
There are some other coloring surface treatments for steel, steel bluing for example, or thin rust-like coatings that aren't friable, maybe even thin plating of shiny metals. 

But from the context, you seem to want to turn the mass of metal, into a vibrant primary color.  That may be possible ...as surely as we can have gold that's cheap to acquire, or lead that isn't heavy, or a steel bar no one can bend, that is to say, purely in the realm of fantasy.

Since you want to learn something about the concrete casting process, by a destructive analytical method, and not use it later for dimensional purposes, maybe you can use colored plastic fibers?
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline wildfyr

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Re: Coloring Steel chemically.
« Reply #4 on: July 11, 2018, 01:02:04 PM »
There are some truly powerful colors that can be gained from anodizing

https://www.colormenuts.com/listing/532596144/anodized-colored-aluminum-hex-nut-516-18

Offline Sarhil

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Re: Coloring Steel chemically.
« Reply #5 on: July 12, 2018, 03:43:45 AM »
This fiber detecting procedure will be done after some mechanical tests and having some cracks. This is why I must use the steel fibers and not another red plastic fibers.

My idea was simple that I can color the fibers over the surface after cutting, in the same manner like rust.

I found a lot of ideas also how to detect iron in a solution like the following link https://en.wikipedia.org/wiki/Prussian_blue but nor sure if this will work on a surface.

Thank you for your help.


Offline Enthalpy

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Re: Coloring Steel chemically.
« Reply #6 on: July 13, 2018, 07:53:47 AM »
Dip the fracture surface in molten metal, like Sn or Sn-Pb, Sn-Cu-Ag... The brilliant metal with wet only steel and increase the contrast with concrete. Depending on how old the fracture is, wetting may take several seconds. Alloys liquid at room temperature exist, like Ga-In-Sn "Galinstan", or just above room temperature like "Woods metal".

Anodisation comes in many colours but I've seen it for aluminium up to now, not steel. Depositing aluminium first is less easy than other metals.

Offline shazeb

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Re: Coloring Steel chemically.
« Reply #7 on: July 14, 2018, 07:05:03 AM »
Chemical coloring of metals is the process of changing the color of metal surfaces with different chemical solutions.

According to David Fishlock, Basically there are only two methods of coloring a metal

electroplating - coating the metal with some other metal by means of a process such as electrodeposition
patination - converting the metal surface into an oxide or salt which is colored or capable of absorbing coloring materials, or which produces color by interference.

Offline Enthalpy

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Re: Coloring Steel chemically.
« Reply #8 on: July 15, 2018, 02:56:25 PM »
According to David Fishlock, Basically there are only two methods [...]

How come a bell rings every time I read "all the methods are", "the only possibility", "proven impossible" and the like?

Maybe I'm getting old and have seen enough inventors find solutions where other people saw only impossibilities.

Or maybe we don't live in a mathematical theory where proofs are possible.

Offline pcm81

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Re: Coloring Steel chemically.
« Reply #9 on: July 16, 2018, 07:30:16 PM »
Are your test specimens already made? If not, may be you can mix a colouring agent into cement to make it, say green, then steel will be different colour. You can try to rust the metal with some HCl, but that may stain the cement with rust run-off. You may have decent luck with electroless nickel deposition or phosphate bath, both of which are weak enough solutions not to eat away at cement too badly.. Not sure if hot black oxide bath would eat away at cement. If you want to try it i use 5lb of sodium hydroxide and 2lb of sodium nitrate per gallon of water, running at 290 degrees F.

Offline pcm81

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Re: Coloring Steel chemically.
« Reply #10 on: July 16, 2018, 07:37:33 PM »
Another possibility would be to take some fine grain powder of some colour like green. rub the surface with it and then use compressed air to blow it off. The theory is that powder will blow off the smooth metal surfaces at lower pressure than from porous cement surface, hence giving you colour differential.

Offline Sarhil

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Re: Coloring Steel chemically.
« Reply #11 on: July 20, 2018, 04:48:16 AM »
Thano you all

I will try your ideas and inform you what is really working.

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