Q: Good afternoon. We have MAG1 here made by Makino that are foaming like crazy. Our coolant supplier came with the solution to add calcium acetate to resolve the issue. While the addition of calcium acetate is indeed working, we are having a hard time to balance the calcium concentration between our machines. They have individual recirculation tanks filled by a common tank when needed. Some of our machines are running as high as 600 ppm of calcium. This is problematic because it can make calcification which is very hard to remove in the system. We are also working aeronautic aluminum with a lot of magnesium in it which should harden the water as well. So these 2 variables makes the calcium concentration hard to measure with hardness sticks (we need lab tests and on 14 problematic machine it's not an option). I was wondering why the calcium acetate would break the foaming. I know by Dom's article that the bottle test wasn't the best (and I agree since it is static and in a closed environment with no real content motion), we can clearly see that there is no foam at all when the calcium is added. Without calcium, the foam takes about 10 seconds to vanish in the bottle. Any clue on this? Is adding calcium a viable defoam solution?

A: The short answer is yes Calcium Acetate is a viable defoamer. I assume your tap water is soft and as such that there is not enough Ca & Mg to react with the fatty acid package in the metalworking fluid. Based on your question I am assuming you have single sump machines and that you are adding the Calcium Acetate with the makeup fluid that would account for the 600 ppm Ca readings on the hardness test strips. I recommend the following:

1. Check the hardness of your makeup water (you may already know this).

2. Add enough Calcium Acetate in each machine to bring the hardness up to 100 to 150 ppm more or less - whatever works.

3. Do not add any Calcium Acetate to your make up fluid.

4. Monitor the hardness of each machine tank using hardness test strips. When the hardness reaches 300 to 400 ppm (hopefully this will take a long time) change the fluid in that machine and return to step one.

Good Luck!
Dom (The Bomb) Ruggeri

MORE ANSWERS -

My feeling is adding CA acetate mucks up all the chemistry in that you can cause soap scum as well as break the emulsion, both bad. It is a double edge sword in that CA hardens and soaps out killing foam but causes scum and instability. Better in my mind to take a look at the fluid system to see if your piping filter flow rates can be adjusted to reduce foam and then look into a lower foam fluid also there are real good tank side AFs out there than will solve the problem the easy way.

Answer courtesy of Bruce (Toots) Fornesi