The most important ingredient in a water-based metalworking fluid may, in fact, be the water. Two shops with identical processes can have widely different experiences with the same metalworking fluid because of differences in water quality. One shop gets great results. The other has serious problems. The coolant foams or forms scum. Oil skimmers or swarf filters don’t work well. Parts exhibit poor surfaces or suffer from corrosion.

Pico Chemical Corp. (Chicago Heights, Illinois) is a manufacturer of specialty chemicals and lubricants to clean, condition, lubricate and protect metalworking, metal forming and related processes. Bob Trivett, a senior chemist at the company, has more than 20 years of experience in the chemical/lubricant industry for metalworking applications. He is responsible for formulating various fluids and metalworking compounds and for servicing customers.

Water quality is a major concern for Mr. Trivett. He stresses that when developing metalworking processes involving the application of a water-soluble fluid, it is critical to understand all of the variables that can affect the process, including the water used for both charging and replenishing the system.

Unfortunately, Mr. Trivett finds that many shops neglect water quality and fail to understand its importance to the proper performance of a metalworking fluid. He offers the following recommendations for shops seeking to prevent problems and improve productivity by optimizing their use of coolants and other fluids:

1. Don’t take water for granted. Recognize the significance of water quality and appreciate its complexity.
2. Learn about water quality and its effect on a fluid’s performance. Water is rarely pure H2O. Other materials in the water affect its chemical and physical properties. Ultimately, all have an effect on the fluid’s effectiveness.
3. Have water quality analyzed and monitor it on a regular and continuous basis. Keep results in a database for reference.
4. Set up and maintain the proper water treatment program to ensure that water of the right quality is available in sufficient quantities for charging and replenishing as needed.
5. Stay on top of developments in water treatment as well as formulations of metalworking fluid concentrates.

The goal of a water treatment program is to supply good water quality for the proper performance, biostability and sump life of metalworking fluids. To the left are the critical parameters for water quality and the values that should be achieved.

Developing a water treatment program requires a balanced approach. In many cases, tap water can be used for charging a system, while treated water (preferably treated by deionization or reverse osmosis) must be used for regular “make-up” to compensate for evaporation.