Biocides for Metalworking Fluid Preservation

Water-miscible metalworking fluids provide ideal conditions for microbial growth: nutrients (emulsifiers, fatty acids), water, warmth (35–45°C), and near-neutral pH. Uncontrolled microbial growth leads to: rancid odor, pH drop (<7.5) → loss of corrosion protection, emulsion destabilization, and dermatitis risk.

Key Biocide Chemistries

Formaldehyde-releasing agents (FRAs):

• Oxazolidines and triazines
• Effective against bacteria at 0.05–0.2% active
• Risk: Formaldehyde release may trigger worker sensitization

Isothiazolinones:

• CMIT/MIT: Broad-spectrum bacteria + fungi; restricted in EU cosmetics
• BIT (benzisothiazolinone): Better pH stability for alkaline fluids; 0.05–0.15% active
• OIT (octylisothiazolinone): Broad-spectrum antifungal; 0.02–0.1%

Biocide Rotation

Rotate between FRA-based and isothiazolinone-based systems monthly to prevent resistance development.

Monitoring

• Dipslide test: Weekly; target <10² CFU/mL; >10⁵ = critical
• pH monitoring: Daily; drop below 8.5 = biocide treatment needed

HMEChem supplies biocide blends for metalworking fluid preservation in compliance with EU BPR requirements.