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My Coolant Selects What?

by Dom Ruggeri

March 2005:

In the early nineties I was working for a major formulating house.  The purchasing manager found a very reasonably priced fatty acid ester.  Although this person knew nothing about chemistry, she knew enough to report her findings to marketing rather then the lab.  Marketing analyzed the situation, taking the price of the ester into account, and came to their inevitable conclusion.  If the lab could formulate this ester into six of our biggest selling products, we could save two hundred thousand dollars per year.  I must admit that is a considerable chunk of change.

Since three of the selected products were mine, the project was assigned to me.  As luck would have it, a one-to-one replacement worked fine.  All the specs matched; the lubrication tests were within range; all was well.  The next step was the field trial.

The first of our updated products was placed in a test stand at one of our major accounts.  Because of our great relationship, it was the best place to begin and on the outside chance that something went haywire, it was a test stand.  Unfortunately, we scheduled the test as the customer was dumping and recharging the main system.  The marketing group decided that this was a golden opportunity to give this modified coolant a real test.  I was not happy.

The recharge went as planned and for the first week everything was normal.  I was cautiously optimistic.  The second week was another story - tool life went to pot, part rejects were going up at an alarming rate, and I was on my way back to the customer to salvage what good will remained.  It seemed the salesman did not inform the customer of the minor raw material change.  I performed all the standard coolant control tests.  Everything checked out as fine.  Even the acid split showed the concentration with the normal operating range.  According to the salesman, if I had to take this back to the laboratory, we were finished.

I contacted my manager and we agreed there was no other way but to send a five-gallon pail of coolant to the lab for analysis.  The salesman balked.  I informed the customer of my plans, covered the salesman’s tail, and advised them of the ester change.  They were gracious (thank heaven) and we agreed to pay for the dump and recharge of the system using the old product.  All was well again.  Of course the salesman lost some credibility.

Back at the lab we determined that the ester hydrolyzed.  Since this is an equilibrium reaction, the more fresh coolant they dumped into the system, the more reactant they were introducing into the system.  So much for cost savings.

Metalworking fluids are a complex blend of materials.  Some react,  others do not, but each one is there for a purpose.  When the fluid is maintained properly, the fluid functions at its peak.  However, as we all know, when something goes out of control the coolant can cause the end user all kinds of problems.  But what happens when the standard concentration tests indicate all is well?

As we all know, an ester is made from an alcohol and a fatty acid.  Further, hydrolysis under caustic conditions is not favored.  Acid conditions are best, and the more hydrophilic the ester, the more likely it is to hydrolyze.  So how can one tell if this is happening in their coolant?  Normally we would control concentration using total alkalinity.  This method measures the alkaline components of your product and it has withstood the test of time.  However, in the situation above, the ester was breaking down into a fatty acid and an alcohol.  It would stand to reason that as the acid in your coolant increases, the acidity would go up.  Therefore, you should have a calculation for concentration by fatty acid just like the one you use for alkalinity.  Is this method accurate?  Granted it is not as accurate as the alkalinity titration, but if you are adding acid to a coolant emulsion, it is accurate enough to tell you something is wrong.

All you need to do is titrate twenty-five milliliters of emulsion to a phenolthalene endpoint.  Compare the milliliters of tenth normal Sodium or Potassium Hydroxide to a graph where you set up titrations using two, five, and ten percent emulsion concentrations.  Or if the correlation coefficient is greater then 0.97, you can reduce the graph to y=mx+b and just plug in the milliliters of titrant and calculate your concentration by Acid Value.  Of course, you may have to go back into the lab and confirm your findings with an FTIR method.  But more about that another time.

As always, should you have any questions please feel free to e-mail me in care of the magazine.  Till next month.

Good Luck