Electrochemical Etching of Metals

 

Etching metals with electricity

 

Etching of metal is a usefull and widely used method of developing engraved patterns on metal. It is used in jewelry as well as making printing plates. Traditionally, metals such as steel, zinc, copper, and brass where etched in an acid solution after a resist was applied to the metal plate in the desired pattern. The acids that where used typically where nitric and hydrochloric acids or ferric chloride. Although efficient, these acid are highly corrosive, difficult to handle, and produce toxic fumes. Whats more is the environmental impact that these reagents cause when improperly disposed of.

There is a much safer alternative, and that is electrolytic etching. Basically, the metal you want to etch is made the anode or ( ) electrode and a piece of the same kind of metal is made the cathode or (-) electrode. These electrodes are hooked up to a DC power source like a car battery charger or plating rectifier. To get a better picture, visit my electrolytic rust removal lens to see how a typical electrolysis setup can be constructed.

The metal ou want to etch still has a resist on it but there are more options since the mordant is less aggresive. For electrolyic etching, you can use a metal salt that is of the same metal that your etching such as ferrous sulfate for steel, zinc sulfate for zinc, and copper sulfate for copper and brass. Some people use strong solutions of sodium chloride or rock salt. Note I did not say table salt in that it contains additives that would interfere with the etching.

 

Supplies

Supplies To do electroetching of metals does not require a huge investment. In fact you may already have a number of the items in your home or garage. You could use a fancy power supply with digital readout but it is not necessary. A simple battery or a battery charger will suffice. You will need a decent sized container to hold the electrolyte and the electordes, and of coarse the salt you will use in your electrolyte. No matter what you use for your salt, you must use distilled or deionized water to make up the solutions. You will need a cathode made of the metal you will be etching and clamps and connectors to hook it all up to the power source.
 

Sodium Chloride

Kosher salt Sodium chloride or common salt is a common electrolyte for etching. For etching steel, it is recommended that you add some vinegar to the salt water electrolyte as this reduces the build up of insoluble rust in the electrolyte.

Ordinary table salt is not recommended due to the additives. You are better off with either Kosher salt or rock salt for ice cream making. Also, you want to use distilled water and not tap water.

 

Iron sulfate for steel

Iron sulfate or copperas from garden supplies If you are going to etch steel , then one option is iron sulfate. This chemical can be had inexpensively at many dedicated garden centers. It may be called copperas as this is an outdated latin name for the product. Its main application is supplying iron to plants and acidifying soil. For use as an electrolyte, a little sulfuric acid may be handy but it will not take much. To make a batch of electrolyte, you would use 200 grams per liter of distilled water.
 

Copper sulfate

Copper sulfate This is blue crystaline salt of copper with sulfuric acid that forms acidic solutions. It is useful as an electrolyte in etching brass and copper. It is also possible to use for steel and zinc but a heavy deposit of copper will form in solution. It is also useful for many other things as seen in my lens about copper salts.
 

Links and resources

Nontoxic Print
A printermakers website using newer ecofriendly and less hazardous chemistry to etch metals such as aluminum, zinc, copper, and steel
Steampunk Workshop
A comprehensive website covering techniques and resources needed for electrolyic etching of brass with copper sulfate.
Green Art Info
A website dedicated to the history and development of electroetching metals without acids

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