Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
D6356 – Standard Test Method Technical Guide
🚧 Overview and Significance
This standard, formally designated D6356/D6356M – 98 (Reapproved 2024), establishes a definitive test method for measuring the hydrogen gas generation potential of aluminum emulsified asphalt coatings used for protective roofing applications. The procedure is essential for evaluating coating formulations and assessing their propensity to generate hydrogen gas, a reaction that must be avoided to ensure coating stability and performance. By measuring the volume of gas evolved under controlled conditions, manufacturers and specifiers can reliably determine the quality and safety of the product in accordance with standard practices.
⚙️ Apparatus and Test Procedure
The test apparatus consists of a 250 mL wide-mouth glass Erlenmeyer flask connected to a glass jacketed condenser and a 100 mL graduated burette (with 0.2 mL divisions and a glass stopcock). A J-tube, formed from standard glass tubing (6.35 mm ID, 7.94 mm OD, 127 mm length), facilitates the connection using pure latex amber rubber tubing (6.35 mm). A No. 8 neoprene rubber stopper with one hole provides a gas-tight seal. The sample, 200 g of the water-based aluminized coating, is placed in the flask and heated to 51.7 ± 1 °C [125 ± 2 °F] using a constant temperature oil or water bath. Temperature monitoring is performed using an ASTM 15C or 15F thermometer as prescribed in Specification E1.
| 🟦 Component | 📏 Specification |
|---|---|
| Sample Container | 250 mL Wide-Mouth Glass Erlenmeyer Flask |
| Gas Collection Device | 100 mL Glass Burette (0.2 mL divisions, glass stopcock) |
| Condenser | Glass Jacketed Condenser |
| Connection Tubing | Pure Latex Amber Rubber, 6.35 mm [1/4 in.] |
| J-Tube | 6.35 mm ID / 7.94 mm OD, 127 mm length |
| Stopper | No. 8 Neoprene Rubber (one hole) |
| Thermometer | ASTM 15C/15F (-2 to +80 °C / 30 to 180 °F) |
⚠️ Critical Safety Advisory: Hydrogen gas is highly flammable. This test must be performed in a well-ventilated area, ensuring no ignition sources are present. The entire apparatus assembly must be rigorously checked for leaks prior to heating to prevent hazardous gas accumulation.
📊 Test Conditions and Monitoring
The test is conducted over a duration of 168 hours (one week). During this period, the volume of hydrogen gas evolved must be recorded at precise 24-hour intervals. A reading taken every 24 hours provides the data necessary to plot the gas generation rate. To ensure volumetric accuracy, the test room must be maintained at a temperature of 73.4 ± 3.6 °F. This controlled environment standardizes the gas collection temperature in the burette receptacle, accounting for thermal expansion and ensuring precise volume measurements across the entire duration of the test.
| 📐 Test Parameter | 🎯 Specified Value |
|---|---|
| Sample Mass | 200 g |
| Heating Bath Temperature | 51.7 ± 1 °C [125 ± 2 °F] |
| Total Test Duration | 168 hours (7 days) |
| Measurement Frequency | Every 24 hours |
| Ambient Room Temperature | 73.4 ± 3.6 °F |
💡 Technical Best Practice: The constant temperature circulating bath must provide stable, uniform heating. Fluctuations in bath temperature can directly affect the reaction kinetics of the aluminum pigment and water, leading to non-representative gas generation rates. Always verify the thermometer calibration against Specification E1 before starting the procedure.
❓ Frequently Asked Questions
🔍 What is the primary purpose of ASTM D6356?
The test method measures the hydrogen gas generation potential of aluminum emulsified asphalt coatings. It evaluates the stability of the coating formulation by quantifying the volume of hydrogen gas evolved from the reaction of water with the aluminum pigment.
💡 What is the required sample mass and test temperature?
The standard requires a 200 g sample of the water-based aluminized coating to be heated to a precise temperature of 51.7 ± 1 °C [125 ± 2 °F] in an Erlenmeyer flask for the duration of the test.
⚡ How long does the test last and how often are measurements taken?
The test is conducted over a full week (168 hours). Gas volume readings must be taken every 24 hours using the 100 mL graduated burette to track the generation of hydrogen gas over time.
📌 Why is the ambient room temperature strictly specified in the test method?
The test room must be maintained at 73.4 ± 3.6 °F to standardize the temperature of the gas collected in the burette receptacle. This ensures volumetric measurements are consistent and accurate across different testing environments and eliminates errors from thermal expansion.