In some metalworking fluid mixes, the presence of MOLD may be a cause of ammonia odors.  The presence of ammonia odors may be noticed if mold and or bacteria digest nitrogen compounds found in metalworking fluids.

Metalworking fluids can be controlled, and actions can be taken that will help avoid ammonia odors:

  1. Maintain your metalworking fluid mix concentration within the established parameters.
  2. Except when using a specialized product that may be designed to operate at a pH of less than 8.8, maintain the pH of the metalworking fluid mix between 8.8 and 9.2.
  3. If you are using a metalworking fluid that contains a triazine compound (such as Grotan) or are using a triazine compound to control bacteria, try to maintain the Grotan levels at 1:750.
  4. Use a culture dip-stick to determine the level of bacteria and the effectiveness of the triazine material.  Remember that these sticks are not as reliable when predicting mold growth.
  5. If bacterial growth is found by the dip-stick, make sure the pH is >8.5 and add a bactericide. 
  6. If the pH is <8.5, adjust the pH to >8.5 by slowly adding liquid caustic.  (Be Careful!).  When liquid caustic is added, there may be a release of ammonia odors if ammonia is present.  Ammonia becomes less soluble in water as the pH increases and the ammonia will be “gassed-off” into the air.  If this occurs, open windows and ventilate the area until the odors are under control.  (A human’s nose can detect ammonia when present at even a few parts per million in air).
  7. It is recommended to separate the bactericide and fungicide additions by about four hours so that there are no compatibility issues.
  8. Once the pH is >8.5, add triazine as recommended by the supplier.  
  9. If no bacterial growth is identified by the culture dip-stick, treat the system with a fungicide (BUSAN 30WB) or a broad–spectrum microbicide (Kathon 886) at the supplier recommended dosage.
  10. Submit samples to your metalworking fluid supplier’s laboratory for a routine analysis at least every two weeks.
  11. Identify the areas of the central system, trough lines, machines, and other prime areas where mold growth may occur.  When identifying these areas, look for areas that have minimum fluid flow, high humidity, and warm temperature. These areas usually show mold growth prior to mold and/or ammonia becoming significant problems.
  12. Remember that you may have both mold and bacteria contamination that are contributing to the ammonia odor.
  13. One clue may be the pH measurement.  If the pH of the fluid dropped very quickly (within hours), the fluid problem is likely bacteria.  If the pH drops slowly over several days or even a week, the fluid problem is likely mold.


Ammonia Odor

If you experience ammonia odors in a metalworking fluid central-system mix, the following actions are recommended.

  1. Treat the system with a fungicide (BUSAN 30WB), or microbicide (Kathon 886) at the recommended concentration. When using Kathon 886, do not add anything to the system except for water for a period of four hours prior and after the dosing. This is to help maximize the effectiveness of the addition.   You should consult the supplier to determine which fungicide is most compatible.
  2. If the mix pH is less than 8.5, adjust it to between 8.5 and 9.0 with liquid caustic.  There are also “buffering” additives available that can be used that will keep the pH adjusted for a longer period of time, as liquid caustic is “quick acting” but not long lasting.
  3. IMPORTANT NOTES: Slowly adjust the mix pH over several hours. Several small doses of liquid caustic at 1:10,000 are recommended over larger  additions. Raising the mix pH can make the ammonia odor worse for a period because the ammonia is less soluble in the higher mix pH. To maintain the desired effects, a pH buffering agent should be added.  Another alternative is to raise the concentration of the metalworking fluid by adding more concentrate for a few days.  This will help buffer the fluid and provide some margin for regaining performance.

  4. Find the location of the mold (biomass) growth and physically remove it.  Try to limit the amount of mold that gets back into the system mix.
  5. If the mix pH does not return to normal (>8.8) by the next day, repeat Steps 1 through 3.
  6. Adjust the mix concentration to within recommended parameters (or slightly higher for a few days).
  7. If the metalworking fluid being used contains triazine, or if a triazine additive is being added to the mix to control bacteria, it may be necessary to increase the frequency of additions to daily or every other day for a few weeks to regain control.  Always follow the supplier’s recommendations.

NOTE:  Some suppliers offer an “Ammonia test” procedure that can be used to test for ammonia present in the fluid mix.  Contact your supplier to get their recommended procedure.

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