How electrifying!

April 10th, 2020
Electrochemical etching is a process to add your own designs onto metal. It etches a design onto a plate by submerging a metal object in an electrically conductive solution and applying electricity as direct current (Harvey et al., 2022). It allows for a low-cost and durable way to engrave on metal.

The theory behind it is simple: a metal plate partially covered in a resist will have the uncovered surface oxidized and in a slight depression (Harvey et al., 2022). The oxidized surface with the depression will create the darker parts of the etch.

I will show a simple process on how to electrochemically etch your own designs onto metal. This post will be focusing on etching on copper; a future post will discuss etching on other materials.

Materials you’ll need:

• Table salt (NaCl)
• A pumice stone (or another abrasive)
• Two copper coupons, one for etching and the other as a “sacrifice” (Cu)
• A bucket of water
• Vinyl and some way to cut a design into vinyl
• Electric tape
• Power supply
• Alligator wires
• Plastic tub big enough to submerge both coupons parallel to each other
• Distilled water (H₂O), enough to cover the coupons in the plastic tub

Disclaimer: I am not responsible for any adverse effects on your health or safety for following this guide. (Plus, this blog was made for a school project and I don't want to get sued, so please do your own research on this topic if you would like to do electrochemical etching.) These instructions are more or less an adaptation of instructions from The Metropolitan Museum of Art, view in references.

Step 1. Pour the water in the bucket and dissolve the table salt in it.

Step 2. Polish the surface of the copper coupon you would like to etch to get rid of dirt and grease

Step 3. Apply the vinyl design onto the copper coupon you would like to etch. Make sure a design has been cut into the vinyl.

Step 4. Connect a wire to the back of the copper coupon. Cover the back and sides with electric tape. Note that all metal exposed to water will be etched.

Step 5. Connect the sacrificial piece to another wire.

Step 6. Connect the plate that you wish to etch to the positive terminal (anode) of the power supply and connect the sacrificial plate (cathode) to the negative terminal.

Step 7. Submerge the plates and turn on the power supply. Leave it in for a while.

Step 8. Turn off the current when you are satisfied with the result (time needed may vary). Do not leave the plates too long as the etching process will start to eat away at metal under the resist.

Step 9. Polish the finished product’s surface with a pumice stone.

And... that's it! You now have an electrochemically etched piece of metal.

The reaction behind it all

May 20th, 2020
After our last blog post, we’ve received many comments and emails asking us how it works. This post will assume that you have some high-school level knowledge of chemistry. Well, to put it simply, electrochemical etching relies on a redox reaction driven by electrolysis.

To break that down:

• Redox reaction: a reaction where electrons are transferred between two compounds (Spohrer et al., n.d.).
• Electrolysis: a method that uses direct electric current to drive a reaction that will normally never happen (Chieh, n.d.).

Besides that more abstract description, I will explain what happens to the atoms, using the metal (Cu) and solution (NaCl) from our previous post. Recall that the process involves submerging a sacrificial plate (Cu), connected to the negative terminal of a DC power supply, and a plate to be etched (Cu), connected to the positive terminal of a power supply, both submerged in an electrolyte (H₂O, Na⁺, Cl^-) solution.

First, the direct current causes the electrons connected to the positive terminal to migrate to the negative terminal, all the way to the sacrificial plate. This causes the sacrificial plate to have extra electrons, giving it a negative charge, and vice versa for the etched plate which has a positive charge and a lack of electrons. Cu becomes Cu²⁺ in the etched plate, which then goes into the solution because the copper ion is soluble in water.

Cu_(s) → Cu²⁺_(aq) + 2e^-

At the same time at the positively charged terminal, or the etched plate, Cl- clusters around because it is attracted to the positive charge. They then give up their electrons to the positively charged terminal to bond with each other, forming Cl₂ or chlorine gas.

Cl^-_(aq) → Cl_2(g) + 2e^-

The copper ions in solution migrate to the negatively charged terminal, which has more electrons, and it ends up taking the extra electrons and attaches itself to the sacrificial plate, because it must become solid as it isn’t soluble in water.

Cu²⁺_(aq) + 2e^- → Cu_(s)

At the same time, the small amount of hydrogen ions in the solution as a result of the autoionization of water also pick up electrons and bond with each other, forming H₂.

H⁺ + 2e^- → H_2(g)

From these reactions we can see that the etched piece of copper will be dented wherever the resist didn’t cover, which creates raised areas wherever the resist was used.

We can also see that it creates gasses that you wouldn’t want to linger around your house. More about that in a later post.

From artisan goods to medical equipment

May 30th, 2020
A subscriber emailed us asking us about where electrochemical etching might be used elsewhere besides for your crafts at home. Well, we’ve got tons!

While you may just think of arts and crafts as something to be done at home, it is often used in industry for adding logos to metal goods like stainless steel. If you see a logo on any metal object, chances are it was done using electrochemical etching.

This process also allows for precise manipulation of the shape (besides the surface) of very thin slices of metals, though it is most effective when used for small things because of the nature of the process (Applications and Benefits, n.d.). For example, it is reported to be used to make focusing tips for microscopes, jigs for ceramic capacitors, and micro-fine filters for filtering (Applications and Benefits, n.d.).

A less common use for electrochemical etching is in the manufacture of printed-circuit boards. Normally, these are etched chemically (without electrolysis) using ferric chloride, but electrochemical etching offers a comparable, if not better quality product than those done with ferric chloride (Electrochemical Etching, n.d.).

Because it generally requires little equipment, it is relatively low cost and a more flexible method of manufacturing meaning it is generally favored over other methods (Applications and Benefits, n.d.). It produces useful goods that improve quality of life like water filters so it has an overall good social impact.

On health, safety, and the environment; and how to deal around these issues

June 30th, 2020
Electrochemical etching may be a great and accessible way to etch onto metal, but that doesn’t mean that it comes without dangers and impacts.

First, we’ll talk about how it may affect the environment. The solution left over from the etching process will contain dissolved ions of whatever metal was etched.

Improper disposal of this solution will result in the metals leaching throughout the environment wherever water is, going into drinking water and bodies of water, thus polluting the environment. From our example, copper pollution was found to increase the effects of ocean acidification and warming on the early life stages of microscopic organisms (Leal et al., 2018).

Next, we’ll talk about the dangers of the etching process itself. From our blog post about how electrochemical etching works, we can see that that specific process using a sodium chloride solution causes chlorine and hydrogen gasses to form. Though not all etching processes will use sodium chloride, all etching processes will in fact form hydrogen because of the hydrogen ions present from the autoionization of water. Hydrogen gas is dangerous because it can cause explosions and fires if not handled properly (Safe Use of Hydrogen, n.d.).

Lastly, we’ll talk about the effects of the etching process on human health. As stated before, the leftover waste from the etching process will pollute the environment if not taken care of properly. From our specific example, copper in drinking water may cause symptoms like headaches, nausea, vomiting, stomach aches, liver damage, and kidney disease (Copper in Drinking, n.d.). In high concentrations, it can damage red blood cells (Copper in Drinking, n.d.).

Luckily, all of these effects can be mitigated. To prevent the wastewater from polluting the environment, avoid pouring the leftover solution down the drain and instead take the leftover to a hazardous waste removal service to prevent it from entering the water system. There are also many strategies in use to remove pollutants like using microfiltration, surfactants, and reverse osmosis to filter the water before humans drink it (Liu et al., 2023).

To mitigate the effects of hydrogen and chlorine gas being produced, we recommend staying in a well ventilated area so that these chemicals don’t accumulate in the air.