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Application · Metalworking

Controlling Bacteria in Metalworking Fluid

ZnoNova Materials

A soluble-oil sump that has gone bad announces itself on a Monday morning. Behind the smell sits a genuine cost: shortened fluid life, disposal charges, corrosion on finished parts, and an operator-exposure question that has become steadily less negotiable.

What is actually happening in the sump

Water-miscible metalworking fluid is a nutrient-rich aqueous system held at a comfortable temperature and aerated by the machine itself. Bacteria colonise it, then fungi follow in the low-flow corners. Bacterial metabolism drops pH, which destabilises the emulsion, which accelerates everything else. Sump-side biocide dosing is the conventional answer, and it works, but it is a repeated intervention against a population that adapts.

What a nano Ag/ZnO additive offers

CompositionNano Ag 1,200 ± 50 ppm + nano ZnO 15,000 ± 200 ppm, waterborne
Particle size / BET5–10 nm · >200 m²/g
Dosage0.5–1% of the concentrate
pH7 ± 1 — will not itself drive the emulsion acidic
DilutionDeionised water only. Chloride in tap water precipitates silver
ComplianceRoHS — free of Cd, Pb, Hg, Cr(VI), PBB, PBDE

Metal-ion antimicrobials act by a different mechanism from formaldehyde-releasing or isothiazolinone chemistries, which is the reason they get looked at in this application at all.

What we will not tell you

Who this page is for

Fluid formulators and blenders evaluating a metal-ion route, and larger end users working with their supplier on a custom fluid. If you are a machine shop with a single bad sump, the answer is almost certainly cleaning and mechanical hygiene rather than an additive, and we would rather say that than sell you a drum.

Questions buyers ask

Can we add this to our existing coolant ourselves?

Talk to your fluid supplier first. Adding an unregistered antimicrobial to a commercial fluid can affect both its regulatory status and its performance warranty, and that is a conversation to have before, not after.

Is it registered as a biocide?

No. We supply it as a functional additive. Biocidal registration for metalworking fluids is a formulator and market-specific process.

How much silver ends up in the sump?

At 0.5-1% of the concentrate, roughly 6-12 ppm silver in the diluted fluid. Disposal implications of metal content in spent fluid are worth checking against your local waste route.

Why can we not dilute with tap water?

Chloride precipitates silver, removing the active. Use deionised, or boiled and cooled, water.

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