You should consider this in conjunction with water-miscible coolants
The functionality of the cooling lubricants you use is significantly influenced by the quality of the water. This is hardly surprising – after all, the water content in emulsions is often over 90 percent, and in solutions even over 95 percent. But what are the key factors to consider?
The pH factor
An important parameter for mixing water is its pH value. A value of 7 is optimal, as the mixing water then behaves neutrally. pH values up to approximately 9 are still acceptable, as long as there are no other reasons against using the mixing water. However, mixing water with pH values < 6 is unacceptable. These can, if necessary, lower the pH value of the cutting fluid emulsion even during fresh mixing – with far-reaching consequences, such as reduced corrosion protection.
A pH level of 7 is optimal.
The total hardness factor
The total hardness is also a crucial factor for optimal mixing water. It is one of the most important application-specific parameters and significantly influences quality. Why is this the case? Water that is too hard can cause the hardness-forming agents present to react with anionic emulsifiers, forming sparingly soluble compounds – known as lime soaps. The consequences: clogged filters and deposits on workpieces, tools, and in machinery. Similarly, mixing water that is too soft is detrimental to emulsions, as it promotes foam formation.
A hardness range between 5 and 20°d is optimal
How can you influence unsuitable water hardness?
Depending on the situation (either a fresh start or a top-up), specific measures will help.
Fresh start
If the mixing water is too soft (< 5° d), we have a special additive for you: The divalent cation content of the mixing water can be altered by adding a Ca²⁺-containing hardener. This measure is usually only necessary for fresh preparations, as the total hardness of the emulsion increases over time.
Repeat dosage:
If the make-up water has a relatively high total hardness, subsequent dosing of the blowdown losses with softened or demineralised water (DI water) is likely to be successful.
Chloride and germs as further influencing factors
When mixing water, also pay attention to a low chloride content. Too high a level primarily negatively affects the corrosion protection properties of water-miscible cooling lubricants. Furthermore, the mixing water should not be microbiologically contaminated. The requirements for this are to be equated with those for drinking water quality.
Our overview for best results
Our tip: Observe specific minimum requirements for the components of the mixing water to achieve the best results. Our overview shows you the crucial data for machining at a glance:
- pH value: approx. 7
- Conductivity (µS/cm): max. 1,000 –1,500
- Total hardness (°d): 5 – 20
- Nitrites (ppm): max. 5
- Nitrate (ppm): max. 50
- Chloride (ppm): max. 250
- Colony-forming units (CFU/ml): max. 10²
