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D1624-71 – Standard Test Method Technical Guide
Acid copper chromate (ACC) is a waterborne wood preservative standardized under ASTM D1624 – 71 (Reapproved 2000). This specification governs the composition, chemical properties, and testing requirements for ACC, whether supplied in a solid granulated form or as a concentrated treating solution. The standard ensures that the preservative provides consistent efficacy against decay and insect attack when used for the preservative treatment of wood.
This specification is under the jurisdiction of ASTM Committee D-7 on Wood and is identical in substance with the American Wood-Preservers’ Association (AWPA) Standard P5 for Acid Copper Chromate (ACC).
🧪 Composition and Chemical Properties
The solid form and the treating solution must meet minimum compositional limits for the primary oxides. The preservative is formulated from water-soluble compounds selected from bivalent copper and hexavalent chromium compounds.
| 🟦 Component | 📏 Minimum (%) | 🎯 Nominal (%) |
|---|---|---|
| Copper, calculated as CuO | 28.0 | 31.8 |
| Chromium, calculated as Cr₂O₃ | 63.3 | 68.2 |
Allowed bivalent copper sources include copper sulfate, basic copper carbonate, and copper oxide. Permitted hexavalent chromium sources include potassium dichromate, sodium dichromate, and chromium trioxide.
⚗️ Treating Solution pH and Analytical Control
Effective wood preservation with ACC requires strict control of the treating solution’s acidity to ensure proper chemical fixation. The specification mandates a specific pH range and outlines the approved analytical method for verification.
| ⚡ Parameter | 📐 Specification |
|---|---|
| pH of Treating Solution | 2.0 – 4.2 |
| Chemical Analysis Method | ASTM D 1627 |
If dichromate is the principal source of chromium, the pH can be adjusted using either chromic acid or acetic acid. Conformance to the composition requirements must be verified through analysis in accordance with Methods D 1627.
📜 Key Considerations and Compliance
The material and its solutions must be analyzed in accordance with Methods D 1627 to confirm the composition falls within the specified bounds. Users of this standard are responsible for determining the validity of any patent rights and the risk of infringement.
⚠️ Critical pH Restriction: The pH of the treating solution shall be not less than 2.0 and not more than 4.2. Deviation from this range can result in poor fixation and reduced preservative performance.
💡 pH Adjustment Guidance: If dichromate is the primary chromium source, chromic acid or acetic acid are the specified agents permitted for pH adjustment to meet the required 2.0–4.2 range.
❓ Frequently Asked Questions
🔍 What materials does this standard apply to?
This standard applies to acid copper chromate (ACC) in solid granulated form and in solution, designated for use in the preservative treatment of wood.
💡 What are the minimum composition limits for the active components?
The minimum copper content, calculated as CuO, is 28.0%. The minimum chromium content, calculated as Cr₂O₃, is 63.3%.
⚡ What is the specified pH range for the treating solution?
The pH of the treating solution must be no less than 2.0 and no more than 4.2.
📌 How is the chemical composition of ACC verified?
The material and its solutions must be analyzed in accordance with ASTM Test Method D 1627 for the Chemical Analysis of Acid Copper Chromate.