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D390-92 – Standard Test Method Technical Guide
🧪 Material Specifications and Physical Requirements
ASTM D390-92 governs the properties of coal-tar creosote used for pressure-treating piles, poles, and timbers. The material must be a distillate derived entirely from bituminous coal tar. The standard provides two distinct sets of requirements: one for general land, freshwater, and marine use (Table 1), and a more stringent set for marine coastal waters (Table 2).
💡 Practical Note: The “Creosote in Use” values account for the accumulation of water and xylene-insoluble matter during treatment plant recycling. New creosote must satisfy the stricter minimum requirements before use.
📋 Table 1: General Creosote Requirements
| 🟥 Property | 📏 Condition | 🎯 New Creosote | ⚡ Creosote in Use |
|---|---|---|---|
| Water, % (max) | Volume | 1.5 | 3.0 |
| Xylene-Insoluble, % (max) | Weight | 0.5 | 1.5 |
| Sp. Gr. Whole (38/15.5°C) | Min | 1.050 | 1.050 |
| Sp. Gr. (235-315°C) | Min | 1.027 | 1.027 |
| Sp. Gr. (315-355°C) | Min | 1.095 | 1.095 |
| Dist. to 210°C (% max) | Weight | 2.0 | |
| Dist. to 235°C (% max) | Weight | 12.0 | |
| Dist. to 270°C (%) | Range | 10.0 – 35.0 | |
| Dist. to 315°C (%) | Range | 40.0 – 65.0 | |
| Dist. to 355°C (%) | Range | 60.0 – 77.0 | |
🌊 Marine Coastal Water Requirements
For timbers used in marine coastal environments, D390-92 mandates higher specific gravity requirements. The heavier oils offer superior resistance to leaching and marine borer attack.
⚠️ Critical Requirement: For marine coastal use, the minimum specific gravity of the whole creosote is 1.080. Additionally, the residue above 355°C must have a specific gravity of at least 1.160, ensuring the retention of high-boiling components.
📊 Table 2: Marine Coastal Creosote Requirements
| 🟦 Property | 📐 Requirement | 🎯 Value |
|---|---|---|
| Sp. Gr. Whole (38/15.5°C) | Min | 1.080 |
| Sp. Gr. Fraction 235–315°C | Min | 1.030 |
| Sp. Gr. Fraction 315–355°C | Min | 1.110 |
| Sp. Gr. Residue >355°C | Min | 1.160 |
| Dist. to 270°C (%) | Range | 20.0 – 40.0 |
| Dist. to 315°C (%) | Range | 45.0 – 65.0 |
| Dist. to 355°C (%) | Range | 65.0 – 75.0 |
| Water, % (volume) | Max | 1.5 (New) / 3.0 (Use) |
| Xylene-Insoluble, % (weight) | Max | 0.5 (New) / 1.5 (Use) |
📐 Governing Test Procedures
Conformance to ASTM D390 is determined using a specific battery of standard test methods that ensure the creosote meets its preservative efficacy and handling requirements.
The distillation characteristics are critical for ensuring the treating oil has the correct viscosity and boiling range to penetrate wood cell structure effectively while remaining resistant to evaporation and leaching in service. The appropriate test methods referenced in this standard include:
- Sampling: Test Methods D38
- Water Content: Test Method D95 (Distillation)
- Insoluble Matter: Test Method D367 (Xylene-Insoluble)
- Specific Gravity: Test Method D368 (Whole Oil) & D369 (Fractions)
- Distillation: Test Method D246 (Distillation of Creosote)
- Corrections: Test Methods D347 (Volume & Sp. Gr. Correction)
❓ Frequently Asked Questions
🔍 What is the scope of ASTM D390-92?
This specification covers new coal-tar creosote, as well as creosote in use during treating operations, intended for the preservative treatment of piles, poles, and timbers for marine, land, and freshwater applications.
💡 What are the maximum water and xylene-insoluble limits for new creosote?
For new creosote, the maximum water content is 1.5% by volume, and the maximum xylene-insoluble matter is 0.5% by weight. During recycling operations, these values may increase to 3.0% and 1.5%, respectively.
⚡ Why does creosote for marine coastal waters require a higher specific gravity?
The minimum whole creosote specific gravity is 1.080 (vs. 1.050 for general use). This ensures a higher proportion of heavy, water-insoluble fractions which resist leaching and provide better long-term protection against marine borers in high-risk coastal environments.
📌 What is the significance of the 315°C and 355°C distillation cut points?
The distillation fraction up to 315°C typically represents the carrier oil that aids wood penetration. The fractions between 315°C and 355°C, and the residue above 355°C, contain the heavier toxic and water-repellent components. The standard carefully balances these fractions to ensure efficacy without excessive bleeding or brittleness.