Electro-etching Metals
NYC Resistor was holding a class on electro etching metals. While I didn't attend their class I did watch some YouTube videos to learn how it works. I am making an Alaskan Ulu knife kit and decided I would try to sign the blade of the knife by electro etching it.
Electro-etching is an easy process and does not involve any high voltages or caustic chemicals.
These instructions appertain to electro-etching soft white metals (is aluminum, tin, mild steel. If you want to etch hard white metals (eg hardened steel, stainless steel) you will have to use more dangerous chemicals and different techniques (I successfully etched stainless steel with just salt water).
There are two techniques you can use. Whichever one you choose you will need a mask/stencil to control which areas get etched and which do not. For instructions on creating a mask see the Acid Etching Glass Wiki page.
Commonalities
Whichever method you choose to use there are certain things that are common.
- As stated above, you will need a mask to control what areas of the metal will be etched.
- You will need an etching fluid. The amount of fluid you will need depends on which method you choose to employ. What makes this technique so easy and environmentally friendly is that the etching fluid employed is a solution of common table salt, vinegar, lemon juice or a combination of the above.
- You will need a source of DC current. You don't need a lot of current. A 9v battery will suffice but for longer, deeper etches a bench power supply would be more appropriate. Use 6-12v DC.
- Areas that are to be etched must be free of paint, grease, oil.
Direct Contact Method
I don't know if this is the proper terminology for this technique but it is descriptive of how the process works.
- Protect the work area and your clothing from liquids.
- Once you have attached your mask to the metal surface to be etched attach an alligator clip to the negative terminal of your power supply and the other end to your metal to be etched somewhere away from the masked etching area so that it makes food electrical contect.
- Attach another alligator clip to the positive terminal of your power source and the other terminal of the alligator clip to the cotton of a cotton swab, AKA Q-tip™.
- Dip the cotton swab into the etching fluid to saturate it.
- Dab the cotton swab over the area to be etched.
- Change cotton swabs frequently as they will quickly become fouled with particles of oxidized metal.
- When you are satisfied with your etching disconnect the alligator clips from your power supply and the etched metal.
- Wash the metal and inspect the etching. If you are still satisfied remove the mask and wash again.
- Dispose of waste materials as normal trash and pour excess etching fluid down the sink.
- Clean up the work area.
| pros | cons |
|---|---|
| can be used on objects in place | etch is not uniform in texture |
| good for small projects | does not etch deeply |
| can provide artistic etch patterns | |
| doesnt require a lot of etching fluid |
Immersion Method
- This method will require a lot more etching fluid as the entire piece of metal is going to be immersed in the fluid.
- Protect the work area from spilled liquids.
- Get a non-conductive container, like a small plastic food container or glass dish, large enough to hold the metal to be etched or at least that portion of the metal which will be etched.
- Fill the container with etching fluid to a level above the area of the metal which will be etched.
- Attach your mask to the metal in the appropriate location.
- Attach a wire to the metal that is to be etched. A hidden area is a good place to make this attachment.
- Cover the entire piece of metal except for the area to be etched with a resist material like electric tape or adhesive vinyl.
- Attach a wire from the negative terminal of the power supply to a sacrificial piece of the same type of metal you will be etching and drop it into the container of etching fluid.
- Attach the wire from the metal to be etched to the posative terminal of the power supply and drop the metal into the container of etching fluid away from the sacrificial metal.
- Wait
- It will take a while and it will be hard to see what is going on as the etching fluid will become fouled with oxidation byproducts.
- When the etch has reached the desired depth disconnect the leads from the power supply.
- Wash the etched metal and inspect. If you are satisfied remove the resist materials and wash again.
- Dispose of resist materials as noral waste.
- Wash and dry the sacrificial piece of metal and place in storage for future use.
- Dispose of spent etching fluid in the toilet and wash the container in the sink.
- Clean up the work area.
| pros | cons |
|---|---|
| can etch more deeply than the other method | requires more etching fluid |
| the etch is more uniform | harder to see what is going on |
| can't be used on objects in place |
