About poor cleaning during metal processing

What is processing oil?

Related article

About oil Vo.1

Many of the artifacts around us are made by cutting, shaving, pressing, punching and stamping.

Processing oils are useful in processing metals as described above.

In the above article, I wrote that “processing oils have different roles, such as preventing friction and imparting lubricity, cooling heat, and preventing rust.” The processing oils are mainly used to extend the life of tools and machine tools used for machining metal.


Processing oil classification and cleaning agents

As described in the article “About oil Vol.1”, processing oils are classified into “oil-based processing oils” that have excellent lubricity and anti-welding properties, and “water-soluble processing oils” that have excellent cooling and no risk of ignition.

After the metal has the desired shape, both the “oil-based processing oil” and the “water-soluble processing oil” need to be washed off.



Compatibility of processing oil and cleaning agent

The two types of processing oil classified above use different cleaning agents depending on whether they are oil-based or water-soluble.

For oil-based processing oils, the following types of cleaning agents are mainly used:

  • Water-based cleaning agent
  • Quasi water-based cleaning agent
  • Hydrocarbon-based cleaning agent
  • Alcohol-based cleaning agent
  • Chlorine-based cleaning agent
  • Bromine-based cleaning agent


On the other hand, there are three types of cleaning agents for water-soluble processing oils:

  • Quasi water-based cleaning agent
  • Hydrocarbon-based cleaning agent
  • Alcohol-based cleaning agent


This time, I will write about the following three types that can remove both oil-based processing oil and water-soluble processing oil:

“Quasi water-based cleaning agent”

“Hydrocarbon-based cleaning agent”

“Alcohol-based cleaning agent”




Characteristics of each cleaning agent

I wrote that I use different cleaning agents depending on whether the oil is oily or water-soluble, but that is not the only point for choosing a cleaning agent.

It is important to identify the scenes and applications in which the characteristics of each cleaning agent can be utilized.


Quasi water-based cleaning agent


  • High-precision cleaning is possible
  • Compatible with many metals and resin materials
  • High safety
  • For non-hazardous substance type cleaning agents, cleaning effect is improved when used in combination with ultrasonic cleaner


  • Burden of wastewater treatment is heavy
  • Requires rust prevention measures for metals
  • High running cost
  • Recycling is difficult
  • Combustible items require management under Fire Service Act in Japan
  • For non-hazardous substances, moisture management is required



Hydrocarbon-based cleaning agent


  • Strong oil dissolving power
  • Low toxicity
  • No worry of metal corrosion or rust


  • It is flammable and requires management under Fire Service Act
  • Not suitable for dirt on solid objects



Alcohol-based cleaning agent


  • Permeability is good and details can be washed
  • Low toxicity


  • Highly flammable and requires management under Fire Service Act
  • Low oil dissolving power
  • Since it is hygroscopic, it is necessary to control the water content




Poor cleaning during metal processing

When cleaning water-soluble processing oil, white solids may adhere as shown in the photo after drying, depending on the cleaning agent.

It is thought that this is because additive components such as extreme pressure agents contained in the processing oil remain without being washed.

Therefore, if you want to wash white solids so that they do not remain, you need to use a detergent that can separate the water containing the additive components from the substrate.


Depending on the compatibility of water-soluble processing oil and cleaning agent, the results may vary even with products that can be washed with each additive component. We recommend that you conduct a comparative test on samples in advance.


Click here for Sankyo Chemical’s water-soluble processing oil cleaning agent

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