Did you know that the type of water used in metalworking processes matters? To elaborate, the quality of water used can impact the performance of the emulsion. This blog will delve deeper into why the quality of water used in metalworking is crucial.
Water Based Metalworking Fluids
Water-based Metalworking fluids (MWF) are designed to be mixed/diluted with water which then produces an emulsion that can be used in various operations to provide lubrication, cooling, corrosion prevention, and the like. The condition and quality of the water used can vary with regard to dissolved salts present and their concentrations.
The component present in the emulsion with the highest concentration will be the water (usually 88.0 – 96.0%) which illustrates the importance of the water being as clean as possible.
MWF emulsions are highly sensitive to the mineral components present in normal municipal water. Understanding the relationship between water quality and metalworking can help ensure optimal performance.
Dissolved minerals present in water:
- Chloride ions:
A high concentration of chloride ions in water used to mix with the MWF product can lead to pitting corrosion on the machine’s ferrous parts and the machine itself. The chloride ion concentration does increase in the emulsion over time as a result of the evaporation of water. A lower concentration of the emulsion is used to increase the volume of fluid in the tank thus adding more chloride ions into the emulsion.
Some stainless-steel materials can be corroded in the presence of high chloride ion concentrations. One can test for the presence and concentration of chloride ions in the water sample by some methods mentioned here: 1) Chloride ion specific photometer (2) Titration with Silver nitrate (Mohr’s method) (3) Chloride ion-specific electrode.
Corrective action: If the water used for mixing with a MWF product was found to have a high concentration of chloride ions then the water must be treated via Reverse Osmosis (RO) or Deionization (DI) to reduce the concentration. It is advised that the MWF emulsion must be regularly tested for chloride ion concentration (chloride build-up over time) and dump the fluid if necessary.
- Water hardness (Ca2+ and Mg2+) and soft water:
The water hardness relates to the concentration of calcium (Ca2+) and magnesium (Mg2+) ion concentration of water. Soft water has a low concentration of these ions and hard water has a high concentration. Soft water can lead to an increased foaming tendency of emulsions. MWF’s contain emulsifiers/surfactants that cause the production of foam. Excess foam can prevent efficient cooling, cause tanks to overflow, bypass filters and damage pumps. The hardness of the water can be tested via titration with EDTA or using test strips. The result is recorded as ppm CaCO3 or °dH.
Corrective action: If the water used is soft with low concentrations of Ca2+ and Mg2+ and excess foam production becomes an issue the corrective action can be to add calcium acetate which would increase water hardness (must be added slowly and within a predetermined concentration range).
- Water hardness (Ca2+ and Mg2+) and hard water:
Hard water has a moderate/high concentration of Ca2+ and Mg2+ and can lead to soaping which is the precipitation of emulsifiers (calcium and magnesium soaps) present in emulsion. These deposits can be deposited on the machine tool and machine which would affect cleanliness; the deposits can also block pipes and filters which is undesired. The precipitation of emulsifiers can lead to instability of the emulsion, poor lubrication and a lower life span of the emulsion.
Corrective action: If the water used for mixing with a MWF product was found to have a high concentration of Ca2+ and Mg2+ then the water must be treated via Reverse Osmosis (RO) or Deionization (DI) to reduce the concentration. One can also choose to use a MWF that is designed to work with hard water.
In short, even the smallest detail is crucial when dealing with metalworking processes and metalworking fluids. It is essential that steps are always taken to prevent corrosion or under-lubrication so that optimal performance is ensured. That’s where we come in. As a leading supplier of metalworking fluids and lubricants, we at Chemical Solutions and Innovations can assist you with all your chemical needs – including providing you with only the highest quality products.
