Alkanolamine pH builders, emulsifiers, and inorganic buffers for water-soluble metalworking fluids — monoethanolamine, triethanolamine, and boric acid — supplied in bulk.
Metalworking-fluid amines are alkanolamines that hold a water-soluble cutting or grinding fluid at the right pH while doing several jobs at once: buffering acid drift, emulsifying oil into water, and protecting ferrous metal from flash rust. Monoethanolamine (MEA, CAS 141-43-5) is the strong, low-cost pH and reserve-alkalinity builder; triethanolamine (TEA, CAS 102-71-6) adds emulsification and yellow-metal-friendly corrosion control. Target a working pH near 8.8-9.2 for most soluble fluids and dose the amine to hold it as the sump ages.
The genuine trade-off is chemical, not commercial. Alkanolamines give a sump long life and good corrosion protection, but with a nitrosating agent present, most often a nitrite-based corrosion inhibitor, secondary-amine content can form N-nitrosamines, a documented metalworking-fluid concern flagged by NIOSH. Primary amines such as MEA form unstable nitroso species; residual diethanolamine in a tertiary-amine grade is the principal precursor. Do not combine nitrite inhibitors with amine-based fluids, and confirm regulatory status for your application and jurisdiction.
Boric acid (CAS 10043-35-3) rounds out the group as an inorganic pH buffer and reserve-alkalinity aid, not an amine, and provides the mild biocidal action that helps hold sump pH and limit spoilage. Keep total water hardness in view, because hard make-up water shifts both pH and emulsion stability. Monitor pH and refractometer concentration weekly, and top up the amine package before pH falls below about 8.5 rather than after corrosion appears.
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