ASTM D4340 Standard Test Method for Corrosion of Cast Aluminum Alloys in Engine Coolants Under Heat-Rejecting Conditions

Get Certified ASTM D4340 Testing for Reliable Engine Coolant Performance

A certified test allows laboratories to determine the effect of coolant corrosion, the corrosion of a coolant under controlled heat and pressure, and to compare weight loss with performance requirements. The test provides a controlled lab measure of resistance to heat-transfer corrosion, but the resistance obtained from ASTM D4340 alone does not indicate long-term service performance. Manufacturers can request additional simulated service, dynamometer, or vehicle testing to complete the evaluation. 

The scope of ASTM D4340 includes:

• Material type: Cast aluminum alloy typical of those used in engine cylinder heads. 
• Test medium: Engine coolant prepared for the test conditions. 
• Purpose: To evaluate the ability of an engine coolant to control heat-transfer corrosion of cast aluminum. 
• Test conditions: The aluminum sample is kept at 135 ± 1°C (275 ± 2°F), and the cell is allowed to reach a final pressure of 193 kPa (28 psi). 
• Exposure period: The test is conducted continuously for 168 hours (1 week). 
• Primary measurement: The method evaluates the weight change of the aluminum test specimen to measure corrosion performance. 
• Replicates: Tests are done in duplicate.
• Application: The method screens unused engine coolants for systems with aluminum cylinder-head components. 
• Limitation: An acceptable laboratory performance is not sufficient to prove good long-term service performance. 

What are the Uses of ASTM D4340 Testing?

ASTM D4340 determines the corrosion protection ability of engine coolants in controlled heat-transfer conditions for use by manufacturers and laboratories. The method:

• Tests the ability of engine coolants to protect cast aluminum alloys from corrosion.
• Assists in screening out unused coolant formulations for aluminum-cylinder-head applications.
• Measures weight loss after changing under controlled heat and pressure.
• Helps determine coolant formulations that can fail to produce sufficient heat-transfer corrosion protection.
• Carries out quality control and formulation development programs.
• Compares corrosion data of various coolant formulations.
• Assists in evaluating the possible impact that corrosion products may have on heat transfer surfaces. 

What Materials Can Be Tested Under ASTM D4340?

The ASTM D4340 utilizes a cast aluminum test specimen based on UNS A03190. The given specimen is about 6.5 cm (2.6 in.) in diameter and 1.3 cm (0.5 in.) thick. The specimen is placed in the laboratory and exposed to the prepared engine coolant while maintaining the aforementioned heat-transfer conditions. This method focuses on the engine coolant formulation and not the general corrosion resistance of any arbitrary aluminum material. The cast aluminum sample is that of aluminum alloys for engine cylinder-head applications. 

Why is ASTM D4340 Important?

ASTM D4340 is used for determining if an engine coolant can protect a cast aluminum component under severe heat-transfer conditions. Corrosion that occurs on heat transfer surfaces can produce corrosion products that will fall on the heat transfer surface and decrease heat transfer during engine operation. This decrease can lead to boil-over and overheating of the coolant. The uniform conditions of temperature, pressure, exposure time, specimen preparation, and evaluation of weight loss offer a uniform basis for screening of coolant formulations. But it is not a comprehensive service-performance test, as it is only being used as a laboratory screening test. 

Testing Procedures and Requirements for ASTM D4340

ASTM D4340 specifies a heat flux across the cast aluminum specimen as it is in contact with the test coolant. Technicians prepare the specimen, prepare the test solution, assemble the corrosion cell, set up the temperature and pressure, and expose it for 168 hours. The method requires duplicate tests. The other referenced ASTM standards include ASTM D1176. The ASTM D4340 testing procedure is as follows: 

ASTM D4340 Testing Process and Data Collection

The ASTM D4340 process starts with the sampling of the engine-coolant concentrate per ASTM D1176. The test solution is prepared, and the cast aluminum specimen is prepared by polishing, cleaning, and vacuum drying. They then weigh the prepared specimen and put it into the heat-transfer corrosion cell. The prepared coolant solution is pumped into the test cell, and compressed air is blown in. The band heater raises the temperature of the specimen, and the pressure is adjusted by the operator to achieve a final pressure of 193 kPa (28 psi) in the system. The aluminum sample is kept at the same temperature (135 ± 1°C) during the 168-hour exposure. Technicians then remove the aluminum specimen and prepare it for final weighing. The weight loss of the second specimen is compared with the weight loss of the first one, and the difference between the two gives an indication of the heat-transfer corrosion performance of the coolant. 

Common Challenges and Troubleshooting

The preparation of the specimen, maintenance of a steady temperature, stable pressure, and the sealing of the corrosion cell are all important for accurate ASTM D4340 results. The amount of change in weight may be influenced by surface contamination, polishing debris, residual moisture, or inadequate drying of the specimen. These problems are minimized by following the cleaning and vacuum drying step specified and by handling the prepared specimens with thin cotton gloves or equivalent protection. Test conditions can also be influenced by pressure fluctuations. A pressure gauge is monitored throughout the test, and a pressure-relief valve and safety shield are provided for safe operation of the pressure gauge. Appropriate seating of O-rings helps prevent leakage from the glass corrosion cell. 

• The weights of the original and final specimens are recorded in a laboratory, and the change in weight is determined.
• The corrosion response is determined after 168 hours of exposure by the analyst.
• Duplicate samples are tested and reported at the laboratory to ensure repeatability.
• The engineer takes into account the controlled temperature of 135 ± 1°C and the final pressure of 193 kPa in the interpretation of the results.
• The manufacturer makes a comparison between the corrosion performance measured and the product specification/customer requirement.
• The smaller the weight loss, the less material is removed from the aluminum specimen under the test conditions.
• The results of the ASTM D4340 screening test do not necessarily indicate long-term coolant service performance. 

FAQs

What does ASTM D4340 measure?

ASTM D4340 tests how well an engine coolant prevents heat-transfer corrosion in cast aluminum alloys. The method assesses the performance based on controlled exposure of an aluminum test specimen to observe the weight change. 

What temperature does ASTM D4340 use?

During the test, the aluminum heat transfer sample is held at 135 ± 1°C (275 ± 2°F). 

What aluminum alloy does ASTM D4340 specify?

The method calls for a specimen of cast aluminum of UNS A03190 and a specimen diameter of ~6.5 cm (2.6 in.) and thickness of ~1.3 cm (0.5 in.). 

Does a satisfactory ASTM D4340 result guarantee long-term coolant performance?

No. ASTM D4340 serves as a screening test in the laboratory. Achievement of a satisfactory result does not guarantee the long-term service performance, and further simulated-service, dynamometer, or vehicle testing may be required. 

Link to ASTM D4340