Coolant changes color

Why does the coolant change color?

During daily machining discolouration of your coolant can occur, but what is the cause, and does it indicate a problem? We have listed a few possibilities below.

Coolant turns green-blue
If a lot of copper and copper alloys are machined, the emulsion/solution can turn green-blue. This has no negative effect on machining. Nonferrous metal chips should nevertheless be removed from the tank at an early stage if possible.

Coolant turns pink
If carbide and PCD are machined with a water-soluble product that is not suitable for these materials, it may turn pink. This is an indicator of dissolved cobalt, which can be carcinogenic. In this case, the cooling lubricant should be changed immediately. Our water-miscible cooling lubricant AquaTec 5001 is designed for machining carbide.

Coolant turns gray
This occurs mainly when the water-soluble product is replaced. The new coolant has a higher cleaning effect than the older fluid and flushes the lines and pipes of the machine free. This is harmless as long as there is no strong odour, which can indicate bacterial infestation. For this reason, we always recommend performing a system clean before changing the cooling lubricant. Other reasons for a grayish discoloration can be dirt particles and chips, or the machining of graphite can be the cause.

Coolant turns brown
If there is a leak in the machine or on one of the lines, hydraulic oil or slideway oil can get into the water-soluble cooling lubricant. These lubricants consist mainly of mineral oil and are of brown colour. If they contaminate the water or a water-soluble coolant, the oil floats on top and appears as brown layer. The tramp oil should be removed with a tramp oil separator.

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