Marking & Etching | Thursday, 01 March 2018

Differences between AC/DC marking and etching – a brief overview

Terms such as ‘marking’ and ‘etching’ are often used interchangeably to describe several related metal branding operations.

When it comes to the electrochemical method, marking and etching are performed with the help of mild electrolytic fluids and electricity.

Depending on the electrical current (AC or DC) used, marking and etching give different results and affect the metal surface differently.

AC (Alternating Current) marking/etching results in a dark mark/imprint on the metal piece – without any changes done to the surface.

On the other hand, Direct Current – DC marking is more similar to engraving – some of the surface is removed through a chemical reaction.

The effect on the metal surface is therefore the main difference between AC/DC marking and etching.

See more details below.

AC electrolytic marking and the effect on the metal surface

Typically, the result of AC marking is a dark oxidized mark on the surface of most metals – stainless steel included.

In most cases, the process only affects the color of the topmost layer of the surface – where the stencil was positioned and the pressure was applied with the help of the marking head.

If performed properly, electrolytic marking leaves the structure of the steel undamaged and causes no corrosion. The resulting mark is crisp, high-definition, and permanent – it can only be removed mechanically through grinding.

The mark may only fade if the surface of the metal comes into contact with strong acids and chemicals.

Electrolytic DC marking and etching

Unlike the AC process, DC etching/marking removes a portion of the upper metal layer and results in an incised light/white mark on the metal surface.

NOTE: Depending on the metal used, AC and DC marking & etching can yield very similar results. For example, aluminum will in both cases provide results that appear to be white.

The etching depth is majorly influenced by the duration of the etching process and the strength of the machine (power unit) used. Typical figure is usually around 0, 0003 of an inch (0, 0076 mm) but this can be adjusted based on different production needs.

As the process involves removal of some of the upper metal layer, it is very important to preserve the molecular stability and ensure that no deformations of the metal surface occur.

This is partially guaranteed by using a DC electrical current instead of the AC one (employed for dark marking). In addition to this, it is recommended to always use material-specific etching acids for consistent and clear results.

AC or DC Marking and etching? What equipment to use for each application?

AC and DC Marking/etching are both widely used in a number of different industries. Thus, the process type depends on your individual needs and preferences.

However, the challenge lies in choosing the correct equipment for optimal results with both processes.

Cougartron has developed a number of practical solutions for electrolytic marking and etching.

Our MK 12 etching and marking system is ideal for smaller workshops and industrial environments – designed for both professionals and hobbyists.

The machine has no distinguished operating modes for marking and etching. Instead, it is automatically set to work with the AC electrical current for marking.

However, with the addition of an adaptor that changes the electric flow from AC to DC – MK 12 is suitable for etching as well.

We are also offering etching kits for our weld cleaning models to make them capable of marking and etching.

With extra consumables added (etching/marking head and fluids), our Cougartron ProPlus is capable of regular dark marking on stainless steel and aluminum.

However, when the power is decreased within the polishing mode – the machine can be used for DC etching as well.