Chemical Etching of Iron and Gold

In summary, the author is researching different etching baths and recommends a 1:2:10 mix of potassium ferricyanide, iodine, and water.
  • #1
G01
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Hello All,

I have a sample which has been covered in a layer of iron and gold for protection. So, in order to work with the sample, we need to etch away the metallic layers. I hear there is a specific chemical recipe for chemically etching away iron and gold from a sample. If anyone can link me to a list of instructions for doing chemical etching of Fe and Au that would be great. Any help at all is appreciated! Thanks.
 
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  • #2
I wonder if both will be not dissolved in the aerated cyanide bath, but that's not a recipe, that's a chemical instinct.

Gold is so strongly complexed by cyanides that oxygen from the air is strong anough oxidizer. Iron doesn't need strong oxidizer, in fact any acid will do, but it is complexed by cyanides as well so it will most likely follow the same path as gold. The only problem is what pH will be the best, as low pH will be deadly (evolving HCN) while high can precipitate iron hydroxide (unless complex is strong enough; that can be easily calculated).
 
  • #3
Aqua regia will etch both; its recipe is readily available online. You MUST wear personal protective equipment (goggles, face shield, apron, gloves) and use proper ventilation equipment, preferably a chemical fume hood.
 
  • #4
Yes, I didn't mentioned it as it will eat through gold, iron and everything else :wink: Cyanide bath - while dangerous too - will be probably more specific.
 
  • #5
Borek said:
Yes, I didn't mentioned it as it will eat through gold, iron and everything else :wink: Cyanide bath - while dangerous too - will be probably more specific.

Good point. G01, what is the underlying sample made of?

Potassium iodide is another good selective etchant for gold.
 
  • #6
Mapes said:
Good point. G01, what is the underlying sample made of?

Potassium iodide is another good selective etchant for gold.

Yes. In the mean time I have done some research and decided that a 1:2:10 mix of I2, KI, and H2O are best for my purposes. I here it's very selective and won't attack the material underneath.

Thanks for the advice!
 
  • #7
That's good. Silicon won't be affected by any of the etchants we've discussed. Good luck!
 
  • #8
Just for the record: I am reading August issue of Journal of Chemical Education and there is a paper that lists several etching baths based on potassium ferricyanide.
 

1. What is chemical etching of iron and gold?

Chemical etching of iron and gold is a process used to selectively remove layers of iron and gold from a substrate using an etchant solution. This technique is commonly used in the manufacturing of electronic components, jewelry, and precision parts.

2. How does chemical etching of iron and gold work?

The process of chemical etching involves immersing the substrate in an etchant solution, which reacts with the iron and gold to dissolve them. The etchant solution is typically an acid or a combination of acids that have a specific affinity for iron and gold. The duration of the etching process varies depending on the desired depth of the etching.

3. What are the benefits of chemical etching of iron and gold?

Chemical etching offers several advantages over traditional machining methods. It allows for precise and intricate designs to be etched onto the substrate, with high levels of accuracy and repeatability. It is also a cost-effective process, as it eliminates the need for expensive tooling and reduces material waste.

4. What are the limitations of chemical etching of iron and gold?

One limitation of chemical etching is that it can only be used on materials that are chemically reactive with the etchant solution, such as iron and gold. It is not suitable for non-metallic materials. Additionally, the etching process can be time-consuming, and the etchant solution may need to be replenished or disposed of after each use.

5. Are there any safety precautions to take when performing chemical etching of iron and gold?

Yes, it is essential to take proper safety precautions when performing chemical etching. This includes wearing protective gear, such as gloves and goggles, to avoid contact with the etchant solution. The process should also be carried out in a well-ventilated area to prevent inhalation of fumes. Proper disposal of the etchant solution is also necessary to avoid environmental hazards.

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