Chemical Etching Technique

With over 30 years of experience manufacturing the Electro-Chemical Etching process we have worked with pretty much every different material and with specifications from all industries. By following the recommendations listed below or contacting our sales and/or technical staff we will definitely help you improve your marking results.

The Electro-Chemical Etching Process is very safe and simple to use. Despite that a very basic Black or White surface etch of 0.0001” to 0.001” depth can pretty much be done by anyone and achieve the best results, if your needs require a deeper etch ranging right up to (potentially) as deep as 0.012” below the surface is pretty much an identical process however the proper techniques can greatly improve the clarity and depth of your results as well as time and efficiency.

AC / DC Current

Using the AC Current Setting will provide Chemical Etching on Stainless Steelyou with what is considered to be a BLACK mark. These results are dependent on the type of material being marked and that the proper electrolyte solution is being used. When operating any of the Millennium Signatures Power Units on the AC current setting, you are in effect extracting material from the surface and re-depositing a black oxide leaving the product with a permanent, stressless mark that will reflect exactly the image of your Paper or Fabric stencil.

While the AC current setting is usually most successful in getting the cosmetic results required for most applications given the contrast of the black mark, the AC setting does not provide as an aggressive reaction with the electrolyte and so therefore it is difficult to achieve greater marking depths on this setting. While the DC current setting creates a much more aggressive reaction with the electrolyte offering greater marking depth, it does not produce an oxide and therefore can be used to achieve any one of the following four results:

  1. If depth is not necessarily required but you are marking a bright and highly reflective material such as a polished stainless steel, the DC setting will actually give you what is considered to be a CLEAR mark as it does not have colour but it results in a matte finish etch against the high polished surface which provides a more easily readable result. In such a case it might seem reasonable to mark such a material with the AC setting providing a black mark, however if the surface is highly reflective the black image although very much there and permanent tends to get lost in the reflection and is not easily visible.
  2. If greater marking depth is required and the marking is going be subject to a coating, paint or anodizing then the best results to achieve the depth effectively would be on the DC setting.
  3. In the event that depth is desired but you also want to have the black mark for the purpose or greater contrast and better visibility, you should use the DC current setting to etch down to the desired depth and then without disturbing the registration of the stencil and the part switch over to the AC current setting for an additional few seconds and you will end up filling the cavity with oxide resulting in a deep and highly visible mark.
  4. In a case where the parts to be marked are Black Oxide coated, the black mark achieved on the AC setting would be mostly undetectable and so switching to the DC setting and using the proper electrolyte (X4R-415 in most cases) will give you the appearance of a WHITE mark against the black surface of the part.


One of the key factors involved when NOT achieving the desired marking depth or doing so with very poor efficiency or mark quality is the breakdown or deterioration of your Monopads and or Paper/Fabric Stencils. The most likely cause of this deterioration is Heat.

The most effective technique allowing you to minimize the heat that is produced while deep etching is to either hold your paper stencil firmly in place or for really deep etch applications it is even suggested that you tape the stencil securely in the proper location and gently rock the carbon head assembly with the monopad attached lifting the head assembly a centimeter or two from the part every few seconds allowing the heat being generated by the reaction to dissipate. There is no need to press the marking head assembly against the part with any force. The marking head assembly with a monopad properly dampened with the proper electrolyte solution just needs to make contact with the surface of the part through the stencil and any additional or aggressive force may only disturb the registration of the stencil or deplete the amount of electrolyte solution being held in suspension by the monopad.

It is also strongly suggested that for really deep etching applications considered to be where achieving marking depths of 0.005” below the surface or deeper two monopads on located directly on top of the other and secured to the Carbon Head with an “O” Ring Clip will provide better results. The two pads will allow more electrolyte to be held in suspension and maintain less heat. If the monopads get too dry, the amount of heat will increase and not only produce poor marking results, but will deteriorate the Paper/Fabric Stencil and Monopads quickly.

After marking several parts the operator will start to notice the discolouration of the monopads. The pads trap micro particles of metal that have been removed in the process as well as some oxide that is produced at the same time. The pads will become flat and lose their absorbency. Once these pad(s) become relatively soiled or no longer hold much solution, they should be removed and washed out by hand.

Washing these Monopads is simple and only takes a few seconds. Simply hold the pads under some warm running water at the sink and using some common liquid soap work to lather with your fingers for a few minutes, then rinse the pads thoroughly and allow them to dry completely before re-using. When you get to the point where the absorbency of the pad can not be restored with washing and the pad is heavily soiled with metal particles and will not clean up at all, it is time to discard the pad(s) and start again with fresh supplies.


Monopads are made with a very Oil- Free Deep Etch Double Thickness Monopadpure material that contains no oils or waxes etc. It is important if you wish to achieve quality results that you use the proper Monopads as opposed to other materials such as regular felt to hold transfer the electrolyte as most other materials do contain colourings, waxes, oils etc., which have proven break down the reaction process and produce poor quality results.

Stencil Care

Paper Stencils are considered to be disposable and require no special care, however a little tip that will help with your marking results especially on standard surface etching applications. Do a short test etch on a sample piece of metal using the DC current setting on a low to medium voltage output to allow the initial reaction and voltage passing through the open aperture of the stencil, in effect cleaning out the aperture and putting the stencil in excellent condition to leave perfect mark the second time on the good part.

Fabric Stencils are designed to produce many hundreds and often thousands of quality markings. There are some things that can be done to properly maintain the stencils. Always make sure that the marking surface is free of solvents or other harsh chemicals that may damage the stencil. Watch to make sure that your part does not have any burrs or metals cutting that might put even a tiny slice in the sheet stencil material. After marking it is a good idea to rinse the stencil under a tap and wipe clean on both sides with a soft non-abrasive cloth and allow to dry. In between parts while marking periodically inspect the stencil to ensure that the open aperture (image) portion of the stencil is still relatively white or semi-transparent and not turning black as the aperture fills with excess oxide created in the process.