chemical treatments used for wood in cooling towers, categorized by purpose and effectiveness:
1. Waterborne Preservatives
Best for: Long-term rot/insect resistance
- ACQ (Alkaline Copper Quaternary)
- Pros: Arsenic-free, widely available.
- Cons: Corrodes galvanized steel fasteners (requires stainless steel).
- CCA (Chromated Copper Arsenate)
- Pros: Superior decay resistance.
- Cons: Toxic (banned in residential uses; restricted in some countries).
- Micronized Copper Azole (MCA)
- Pros: Low toxicity, good penetration.
- Cons: Less effective in high-pH water.
2. Oil-Based Preservatives
Best for: Harsh environments (marine/industrial)
- Creosote
- Pros: Excellent for heavy decay/termite resistance.
- Cons: Banned in some regions; stains water.
- Pentachlorophenol (Penta)
- Pros: Deep penetration, long-lasting.
- Cons: Highly toxic; phased out in many areas.
3. Surface Coatings
Best for: Maintenance & supplemental protection
- Copper Naphthenate
- Pros: Low toxicity, brushes/dips easily.
- Cons: Green discoloration.
- Borates (Timbor, Bora-Care)
- Pros: Non-toxic to humans, antifungal.
- Cons: Leaches out in continuous water exposure.
4. Biocides & Additives
Best for: Algae/bacterial control
- Didecyl Dimethyl Ammonium Chloride (DDAC)
- Pros: Broad-spectrum biocide.
- Cons: Requires regular reapplication.
- Isothiazolinones (e.g., Kathon™)
- Pros: Effective against slime/biofilms.
- Cons: Can degrade wood fibers over time.
Quick Comparison Table
| Treatment | Best For | Lifespan Extension | Toxicity |
| ACQ | General rot/termites | 15–25 years | Low |
| CCA | Extreme durability | 25–30 years | High |
| Creosote | Marine/industrial | 30+ years | Very High |
| Copper Naphthenate | Maintenance coats | 5–10 years | Moderate |
| Borates | Non-water-contact areas | 5–8 years | Very Low |
Key Takeaways
- For new towers: Use ACQ or MCA (balance of safety/performance).
- For harsh conditions: Creosote (if permitted) or CCA (with precautions).
- For maintenance: Copper naphthenate or borate sprays.