A CCA fence post is a wood post that has been pressure-treated with Chromated Copper Arsenate (CCA), a chemical wood preservative designed to protect it from rot, fungi, and insect infestations. This treatment significantly extends the lifespan of the wood, making it highly durable for outdoor applications like fencing.
Understanding CCA (Chromated Copper Arsenate)
CCA is a chemical compound consisting of three primary components, each serving a crucial role in wood preservation:
- Chromium (Cr): This element acts as a fixing agent, helping to bind the copper and arsenic firmly to the wood fibers. This fixation is vital to prevent the active ingredients from leaching out prematurely and to enhance the preservative's long-term effectiveness.
- Copper (Cu): Copper is the primary fungicide and insecticide in CCA. It is highly effective at preventing the growth of decay fungi and protecting against various wood-destroying insects.
- Arsenic (As): Arsenic serves as a powerful secondary insecticide and fungicide, particularly effective against termites and other wood-boring insects. It also contributes to the overall stability and long-term protection of the treated wood.
The Pressure-Treatment Process
The effectiveness of CCA comes from its application through a specialized pressure-treatment process. This method ensures that the preservative penetrates deep into the wood, rather than just coating the surface.
- Preparation: Wood posts are typically dried to remove natural moisture.
- Vacuum Application: The posts are loaded into a large, sealed cylinder. A vacuum is applied, which effectively draws out any remaining moisture from the wood.
- Preservative Introduction: As the moisture is extracted and a strong vacuum (suction) is created, the CCA solution is then introduced into the cylinder.
- Pressure Application: High pressure is applied, forcing the CCA solution deep into the wood's cellular structure. This ensures thorough saturation, providing comprehensive protection against biological threats.
This deep penetration, where the preservative is pulled far into the post, is critical for delivering the long-lasting resistance that CCA-treated wood is known for.
Key Benefits of CCA Fence Posts (Historical)
Historically, CCA-treated fence posts were highly valued for several reasons:
- Exceptional Durability: CCA treatment dramatically increases the lifespan of wood, allowing posts to last for decades even in harsh outdoor conditions.
- Superior Rot and Decay Resistance: The copper and arsenic components effectively prevent fungal growth and wood decay, which are common issues for untreated wood in contact with soil.
- Effective Insect Repellent: CCA provides robust protection against termites, carpenter ants, and other wood-boring insects, which can quickly destroy untreated timber.
- Cost-Effectiveness: Due to their longevity and performance, CCA posts were a very economical choice over the long term.
Current Status and Environmental Considerations
While highly effective, CCA-treated wood has faced significant environmental and health scrutiny due primarily to the presence of arsenic. Concerns arose regarding the potential for arsenic to leach into soil and water, and the risks associated with human exposure, especially in residential settings.
As a result, in 2003, the U.S. Environmental Protection Agency (EPA) reached an agreement with wood treatment manufacturers to voluntarily phase out the use of CCA for most residential applications, including fence posts, decks, and playground equipment.
- Residential Use: Generally, CCA is no longer permitted for residential construction where frequent human contact is expected.
- Industrial and Agricultural Use: CCA is still approved for certain industrial, agricultural, and commercial applications where the potential for human exposure is minimal, and the need for extreme longevity is paramount. This includes utility poles, highway noise barriers, marine pilings, and some agricultural structures.
For more information on the regulations and safety of CCA, refer to the U.S. Environmental Protection Agency (EPA).
Alternatives to CCA for Fence Posts
With the restrictions on CCA, newer wood preservatives have been developed and are now widely used for residential and commercial applications. These alternatives aim to provide similar levels of protection with fewer environmental or health concerns:
- Alkaline Copper Quat (ACQ): This is a copper-based preservative that also includes a quaternary ammonia compound (quat) to enhance fungal and insect resistance.
- Copper Azole (CA): Similar to ACQ, CA uses copper as its primary active ingredient, often combined with an azole compound, which is a fungicide.
- Micronized Copper Quat (MCQ) / Micronized Copper Azole (MCA): These are newer copper-based preservatives where the copper is ground into very fine (micronized) particles. This allows for better penetration and reduced leaching of copper, often resulting in a more natural wood appearance and less corrosiveness to fasteners.
- Naturally Durable Wood: Some wood species, such as redwood and cedar, have natural resistance to rot and insects due to their inherent chemical properties. However, their durability often doesn't match that of pressure-treated wood, especially in ground contact.
- Steel or Composite Posts: Non-wood alternatives like galvanized steel or composite posts offer excellent durability and require no chemical treatment.
Comparison of Modern Wood Preservatives
Here's a comparison highlighting key differences between CCA and its modern alternatives:
| Feature | CCA (Chromated Copper Arsenate) | ACQ/CA (Alkaline Copper Quat / Copper Azole) | MCQ/MCA (Micronized Copper) |
|---|---|---|---|
| Active Ingredients | Chromium, Copper, Arsenic | Copper, Quaternary Ammonia Compound / Azole | Micronized Copper, Quaternary Ammonia Compound / Azole |
| Effectiveness | Highly effective against rot, fungi, insects. | Very effective against rot, fungi, insects. | Very effective against rot, fungi, insects; often better color retention. |
| Leaching Concerns | Arsenic leaching; restricted for residential use since 2003 (US). | Less hazardous than CCA; some copper leaching possible, but generally considered safe for residential use. | Reduced copper leaching due to smaller particle size; generally considered more environmentally preferred. |
| Corrosiveness to Metal | Less corrosive to common steel fasteners than ACQ/CA. | More corrosive to common steel fasteners; requires stainless steel or specially coated fasteners. | Less corrosive than ACQ/CA, but still recommends treated-wood-compatible fasteners. |
| Residential Use | Generally not allowed for residential fence posts and other frequent contact applications (post-2003 production). | Common and approved for residential and commercial outdoor use. | Increasingly popular and approved for residential and commercial outdoor use. |
| Color After Treatment | Often has a greenish tint that fades to grey/brown. | Can have a strong green/brown tint; may not fade as evenly as CCA. | More natural wood appearance; often less green tint than ACQ/CA, fades more uniformly. |
Practical Considerations for Existing CCA Posts
If you have older CCA-treated fence posts or other structures on your property (installed prior to 2004), it's important to handle them with care:
- Do Not Burn: Never burn CCA-treated wood, as the smoke and ash can release toxic chemicals, including arsenic.
- Wear Protection: When cutting, drilling, or handling old CCA wood, wear gloves, a dust mask, and eye protection. Collect sawdust and dispose of it properly.
- Proper Disposal: Dispose of CCA-treated wood waste according to local municipal solid waste regulations, typically in a landfill designated for construction debris.
- Painting/Staining: Applying a sealant or stain can help reduce the potential for chemical leaching from the surface.
- Avoid Contact: Try to minimize direct, prolonged contact with CCA-treated wood, especially for children.
For further guidelines on handling treated wood, consult resources from the American Wood Protection Association (AWPA) or your local environmental protection agency.
