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D1625-71 – Standard Test Method Technical Guide
📋 Standard Overview and Scope
This specification, designated as D1625-71 (Reapproved 2000), covers chromated copper arsenate (CCA) formulations expressed on an oxide basis. These formulations are available in solid, paste, or solution form and are used for the preservative treatment of wood. The standard is under the jurisdiction of ASTM Committee D-7 on Wood and is identical in substance to the American Wood-Preservers’ Association Standards for Acid Copper Chromate (ACC) in Sections 4, 5, and 6 of AWPA P5-96.
🧪 Composition and Properties
CCA preservative formulations must meet specific composition requirements calculated as oxides. The physical form may be a dry solid, semi-liquid paste, or solution. The composition for the three types — A, B, and C — is listed in Table 1. Additionally, the composition may vary within the limits specified in Table 2.
| 🟦 Component | 📏 Type A (%) | 📐 Type B (%) | 🎯 Type C (%) |
|---|---|---|---|
| Hexavalent chromium as CrO₃ | 65.5 | 35.3 | 47.5 |
| Bivalent copper as CuO | 18.1 | 19.6 | 18.5 |
| Pentavalent arsenic as As₂O₅ | 16.4 | 45.1 | 34.0 |
| ⚡ Type | 🟦 Component | 📏 Min (%) | 📐 Max (%) |
|---|---|---|---|
| Type A | CrO₃ | 59.4 | 69.3 |
| CuO | 16.0 | 20.9 | |
| As₂O₅ | 14.7 | 19.7 | |
| Type B | CrO₃ | 33.0 | 38.0 |
| CuO | 18.0 | 22.0 | |
| As₂O₅ | 42.0 | 48.0 | |
| Type C | CrO₃ | 44.5 | 50.5 |
| CuO | 17.0 | 21.0 | |
| As₂O₅ | 30.0 | 38.0 |
🔬 Chemical Analysis and Validation
The chemical analysis of CCA materials must be conducted in accordance with Test Methods D 1628. The preservative product must be labeled with its total content of active ingredients as specified in Table 1. The compounds used must be water-soluble and have a purity exceeding 95% on an anhydrous basis.
💡 Key Note: The ingredients for CCA must include hexavalent chromium (e.g., potassium or sodium dichromate), bivalent copper (e.g., copper sulfate), and pentavalent arsenic (e.g., arsenic pentoxide), each with over 95% purity.
⚡ Important: Always follow the specified composition limits to ensure the preservative’s efficacy. The types A, B, and C have distinct oxide ratios that define their properties.
❓ Frequently Asked Questions
🔍 What is the scope of ASTM D1625-71?
This standard specifies chromated copper arsenate formulations for wood preservative treatment, covering types A, B, and C on an oxide basis.
💡 What are the purity requirements for the compounds?
All compounds must be water-soluble and have a purity greater than 95% on an anhydrous basis, as stated in Section 3.3.
⚡ How is the composition verified?
Composition verification is performed using Test Methods D 1628 for chemical analysis, as referenced in Section 4.1.
📌 What are the types of CCA and their differences?
There are three types: A, B, and C, each with specific oxide compositions for chromium, copper, and arsenic. Type A has high CrO₃, Type B has high As₂O₅, and Type C has balanced mixtures.