Though many different types of metals may be etched, aluminum is one of the most common materials used in modern etching contexts. Also spelled aluminium, this is one of the most abundant metallic chemical elements found in the Earth’s crust and the third most plentiful of all elements. Its strong affinity to oxygen, however, makes its free form presence rare in nature.
Aluminum is extracted from ores such as bauxite using the Hall-Heroult method. While mining and refining this metal can be difficult, it is easily manufactured and 100% recyclable without any loss of its natural qualities.
Extreme malleability, corrosion resistance, ductility, strength and thermal and electrical conductivity make aluminum sheets, plates, strips and foils prime candidates for etching and engraving processes.
While hobbyists and artists frequently utilize aluminum etching, industrial and commercial manufacturing also incorporate this medium in a variety of applications. Transportation, aerospace, construction, electrical and medical industries all integrate aluminum etching in metal components.
Products such as castings, tubes, construction hardware, cooking utensils, watches and heat sinks frequently include etched aluminum components.
Such a wide variety of aluminum etched products reflects the many different etching techniques available. While hand etching with a needle is still popular in artistic and custom applications, chemical etching or machining is the most common industrial etching method, particularly acid etching and photofabrication.
Acid etching is accomplished by covering the aluminum surface to be etched with an acid resistant waxy ground such as asphaltum. The manufacturer scratches off the ground, using a point etching needle creating the design of the finished piece.
The aluminum sheet is then dipped into acid or has acid washed over the metal. Photofabrication follows a similar procedure but rather than a waxy ground, the aluminum is covered in a photoresist and exposed to UV light to create the template necessary before the corrosive chemical is applied.
In either instance, the chemical wash bites into the metal where it is unprotected, leaving a depression in the plate. The depth of the groove depends on the length of application.
When the desired depth is achieved, the remaining chemicals are washed off and the rest of the wax or photoresist is removed to reveal the finished product. Sodium hydroxide is the chemical most often used with when etching aluminum.