/// Electrolyte Handling System (EHS)

The Electrolyte Handling System (EHS) is a semi-closed system - that is, the electrolyte used for the pECM machines is reused almost indefinitely and refilled when necessary.

During the pECM process metal is dissolved. By the introduction of membrane filtration systems, particles can be removed from the electrolyte by filtration. Also the pH level is controlled to create a constant quality of the electrolyte, the dissolving coefficient of the metal ions is strongly depending on the pH. This value should be as low as possible for all metal ions to prevent plating of these ions to the electrode or to prevent the formation of black or brown oxides on the tool. In addition, the conductivity is an important parameter for the pECM process and is strongly depending on the Temperature. Electrolyte systems need to be equipped with a sufficient Temperature control system and electrolyte cooling to maintain a constant electrolyte conductivity. Finally, when alloys containing certain levels of Chromium are machined, it is very likely that the Chromium dissolves to the toxic and carcinogen Cr(VI). That is why there are certain reduction agents, along with different techniques which are known to be capable of reducing the Cr(VI) to the non-toxic Cr(III)*.

A/N: Cr(III) is not harmful because it forms Chromium hydroxide and would eventually be filtered out by the electrolyte system.

Applying the above described cleansing techniques and controlling the electrolyte within specified pH and temperature limits is attributing to the required quality of the part and the process. A precise and reliable pECM process requires a constant quality of the electrolyte to manufacture a constant quality of products.


The Electrolyte Handling System (EHS) comprises of the following elements*:

  1. electrolyte handling part
  2. filtering unit
  3. rinse water handling system

The combination of those elements varies depending on the client's product requirements.


The Electrolyte system inputs are the following: dirty electrolyte flow from the ECM machines; Nitric acid (HNO3) solution for dosing for the pH control; Sodium nitrate (NaNO3) solution dosing for conductivity control; Rinse water supply to fill the system. In addition to those other important factors affecting cleaning efficiency are: concentration, cleaning time, temperature, and hydrodynamic conditions during the cleaning.

/// Brief History

The first generations of pECM machines (1950-1990) were not making use of electrolyte cleansing techniques. The electrolyte was used until it was saturated with (residual) products from the reaction, such as metal ions, metal oxides and hydroxides, and in most cases even with the toxic Cr(VI). As a result of the amount of those particles in the electrolyte it was impossible to machine smaller than 100 micrometer gaps (< 100) gaps at that time.


ECM Technologies has gained skills and knowledge capacity on cleansing systems and electrolyte control through working with a variety of materials' electrolytes and developing a number of electrolyte treatment systems.

Should you want to know more about Electrolyte Handling Systems or are interested in acquiring one for your manufacturing processes, please feel free to contact us.