ASTM D1384-04 Standard Test Method for Corrosion Testing of Engine Coolants in Glassware

The standard 'ASTM D1384-04 Standard test method for corrosion testing of engine coolants on glassware' developed by the American Society for Testing and Materials (ASTM) describes a simple beaker-type procedure for evaluating the effects of engine coolants on metal specimens under controlled laboratory conditions.

In this test method, metal samples typical of those found in engine cooling systems are completely immersed in the viewing area and are available for further evaluation. However, the results of this test method cannot stand alone as evidence of satisfactory corrosion inhibition. The true service value of an engine coolant formulation can only be determined by more extensive bench, dynamometer and field testing.

The main equipment used in these tests includes:

• Vessel: A 1000 mL, tall, mouthless beaker made of heat-resistant glass, containing the engine coolant solution and test samples. The beaker should be tightly closed with a No. 15 rubber stopper with holes drilled to accommodate a water condenser, a breather tube, and a thermometer as shown.
• Condenser: A water condenser with reflux, glass tube type, 400 mm condenser jacket.
• Aerator tube: A gas dispersion tube with a pore size of 12-C to ensure continuous aeration without clogging.
• Thermometer: An ASTM partial immersion thermometer having a temperature range of minus 20 degrees to 150 degrees and complying with the requirements for thermometer 1C as specified in the ASTM E1 standard.
• Heater: A constant temperature bath containing a high boiling point liquid capable of continuous service with specified temperature control. The size of the bath is determined by the number of corrosion tests to be run simultaneously.

The specifications specified in this test method have been accepted by automobile manufacturers, but their composition may not be the same as that of alloys currently used for engine cooling system components. Therefore, samples other than those specified in this test method may be used by mutual agreement of the parties involved.

In preparing test specimens, cast iron and cast aluminum specimens with cut surfaces measuring 25,4 mm x 50,8 mm are sanded with coarse grade (No. 1) emery cloth. Burrs are removed from coupon edges and holes. All specimens are brushed vigorously using a damp bristle brush and ground pumice powder or fine silicon carbide grit until the entire metal area is bright, shiny and free from visible oxide film or tarnish.

Samples are rinsed thoroughly with tap water, then rinsed with acetone, dried and weighed to the nearest 1 mg. Cast aluminum samples should be dried to constant weight in a 100°C oven for 1 hour before recording the weight. If test samples are not used immediately, they are kept in a desiccator until needed.

The concentration of the engine coolant to be tested should be:

• Engine coolant: EG or PG base engine coolant is mixed with an appropriate amount of corrosive water to obtain a 33 1/3 volume percent coolant test solution.
• Corrosive water: Corrosive water should contain 100 ppm each of sulfate, chloride, and bicarbonate ions added as sodium salts.

The sample is prepared in accordance with ASTM D1176, 'Preparation of solutions requiring inclusion of separated solids and liquids'. However, caustic water is used for dilution instead of distilled water. Therefore, all insoluble material is included in the representative sample. The specified caustic water can be prepared by dissolving the following amounts of anhydrous sodium salts in distilled or deionized water:

• Sodium sulphate 148 mg
• Sodium chloride 165 mg
• Sodium bicarbonate 138 mg

The resulting solution should be completed to a volume of 20 L with distilled or deionized water at 1 degrees.

If relatively large quantities of corrosive water are required for testing, a concentrate can be prepared by dissolving ten times the amount of the above three chemicals in distilled or deionized water and adjusting the total volume to 1 L by adding more distilled or deionized water. If necessary, the water concentrate is diluted to a ratio of one volume part of the concentrate to nine volume parts of distilled or deionized water.

The test conditions are as follows:

• Cup mounting: The arrangement of the mounted metal samples in relation to the vent pipe and other components is shown in the figure. It should be noted that the end of the condenser protrudes just below the rubber stopper.
• Test temperature: The test solution should be kept at 88 degrees plus/minus 2 degrees for high boiling point engine coolants.
• Ventilation rate: The ventilation rate should be 100 mL/min plus/minus 10 mL/min. The ventilation tube should be at least 12,7 mm away from the test beam to avoid direct contact with metal samples.
• Test duration: The test must be run continuously for 2 weeks (336 hours).

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