ASTM D1122 Test Method for Density and Relative Density of Engine Coolant Concentrates and Engine Coolants by the Hydrometer

Get Certified ASTM D1122 Testing for Reliable Engine Coolant Quality 

Manufacturers use relative density testing, which is certified per ASTM D1122, because relative density affects the accuracy of dilution, glycol dosing, and freeze and boil protection in the finished product. A batch of coolant concentrate, before it leaves the plant, is certified to meet the formulation specification. This verification process allows the producer to fine-tune their blends for maximum performance, minimize field failures, and ensure consistent field performance. 

• Material type: Engine coolant concentrates, aqueous engine coolants, glycols, glycerin, and heat transfer fluids. 
• Purpose: Evaluation of relative density for quality control and verification of coolant formulation. 
• Properties evaluated: Relative density (specific gravity) at a specified reference temperature. 
• Testing Method: Reading on the hydrometer in a temperature-controlled cylinder at 15.6 °C, 20 °C, or 25 °C. 
• Result: The results include a relative density value (dimensionless) and the reported temperature of the test. 
• Test Limitations: Requires a well-mixed sample with no bubbles, and results are dependent on the accuracy of the temperature control and the calibration of the hydrometer. 
• Use conditions: Testing is performed at a controlled laboratory temperature, not at in-service conditions. 
• Applications: Coolant manufacturing quality control, glycol concentration verification, estimation of freeze/boil point, and heat transfer fluid monitoring.

What are the Uses of ASTM D1122 Testing?

ASTM D1122 testing provides laboratories with a method for comparing the relative density and glycol concentration of raw materials and finished coolant products and for engineers to ensure batch consistency and to approximate coolant performance. This standard-

• Determines the relative density of engine coolant concentrates and finished engine coolants in relation to a fixed reference temperature.
• Assists manufacturers of coolants with production control testing and formulation verification.
• Assists in the estimation of the approximate percentage of glycol within a sample where the type of glycol is known.
• Helps determine the freezing point and the boiling point without conducting a complete freeze-point determination.
• Collaborates in product development and quality control of batch runs.
• Helps to select and test automotive and industrial coolant concentrates.

What Materials Can Be Tested Under ASTM D1122? 

ASTM D1122 is primarily applicable to automotive and industrial cooling systems that use liquid coolant raw materials and finished coolants. This method is commonly used to test ethylene glycol and propylene glycol-based engine coolant concentrates, prediluted aqueous engine coolants, glycerin, and aqueous glycol heat transfer fluids. All of these fluids contain the fundamental relative density data a manufacturer needs to ensure the consistency of heat transfer fluids and coolant dilution and glycol content.

Why is ASTM D1122 Important? 

The significance of ASTM D1122 is that the relative density directly correlates to the freezing point, boiling point, and concentration of glycol in a coolant. A relative density test result outside of specification indicates the batch is under- or over-diluted, which results in the batch not reaching the proper freezing temperature, an insufficient heat transfer rate, or failure to meet the formulation specification. By conducting this test, the manufacturer identifies these issues before the coolant product is sold, avoiding expensive quality problems and assuring field performance. 

ASTM D1122 Testing Process and Data Collection

The analyst selects a representative sample of the coolant/concentrate and defines the set reference test temperature. The technician then conditions the sample in a constant temperature bath and removes any entrained air. The operator places the hydrometer in the cylinder and allows it to rest before taking the reading, then records the relative density. Analysts then make comparisons of the batch data to specifications of the raw materials or finished product. 

Common Challenges and Troubleshooting

Accurate ASTM D1122 results require stable temperature control, clean cylinders, and calibrated hydrometers. When the reading is distorted, it is most likely due to air entrapment, unstable sample temperature, or the hydrometer touching the cylinder wall. Technicians minimize these errors by inspecting hydrometer calibration and temperature monitoring systems before testing, and laboratories get the best results when they sample, condition, and evaluate samples the same way each time. 

• The laboratory reports relative density as a dimensionless value at the specified reference temperature, such as 15.6 °C, 20 °C, or 25 °C, as applicable.
• The technician records the measured relative density, test temperature in °C, reference temperature, and hydrometer scale used during the evaluation.
• The analyst interprets the reported relative density as a single measurement.
• Analysts use calibrated hydrometers, consistent sample conditioning, and controlled bath temperatures to support accurate and repeatable measurements.
• Engineers compare relative density results obtained under equivalent conditions with applicable specifications, reference values, or quality-control requirements.

Link to ASTM D1122