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pH of Metalworking Fluids and Cutting Oils

The pH level of a metalworking fluid is a key indicator of the fluid’s health. Many metalworking fluids have a typical working range of pH between 8.5 and 10.5, making the fluid alkaline. The pH of the fluid affects such properties as:

Corrosion – having the pH in an alkaline range protects ferrous metals from corrosion.

Metal solubility – the pH and reserve alkalinity of the fluid control the amount of metal solubility.

Emulsion stability – the pH has an effect on how tight (higher pH) or coarse (lower pH) the emulsion is, affecting the stability of the emulsion and such properties as wetting and lubricity.

Dermatitis  – when pH gets too high the risk of dermatitis increases as the alkalinity can “saponify” the oil in the skin, causing it to dry out.

Bacterial and fungal growth – while not able to prevent the growth of biological contamination the pH does affect the growth rate, with bacterial growth reducing at higher pH levels and fungus preferring highly alkaline solutions.

Machine tool compatibility – extremese of pH can cause damage to machine tools, elastomers (seals) and plastic components (embrittlement).

By monitoring the pH of your metalworking fluid you can keep it in the optimal level for the system, reducing the negative impacts, improving safety and prolonging the life of the fluid and the machine tools.

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