ASTM D4340 Standard Test Method for Corrosion of Cast Aluminum Alloys in Engine Coolants Under Heat-Rejecting Conditions
11. Procedure
11.1 Assembly - Assemble the cell in accordance with Fig. 1. Use new O-rings between the aluminum test specimen and glass cell for each test. To help ensure that the O-rings are properly seated, apply a small amount ofthe test solution to the glass O-ring groove for lubrication. Avoid overtightening of the threaded rod nuts.
11.2 Starting the Test - Transfer 500 mL of test coolant solution into the test cell, screw the plug in the hole, and tighten. Place the safety shield around the cell, (see Warning) pressurize the cell to 138 kPa (20 psi) with compressed air, and turn the band heater on. Provision must be made for a pressure rise with increase in temperature. Adjust the pressure gradually so that when the temperature reaches the proper value, the final pressure is 193 kPa (28 psi). (Warning - Despite the presence ofa safety reliefvalve, test cells have burst under pressure. Use of a safety shield is absolutely necessary. A clear plastic enclosure, having allowance for adequate circulation of air yet completely surrounding the test apparatus has been successfully used for this purpose.)
11.3 Conducting the Test - Adjust the temperature to 135 +/- 1°C (275 +/- 2°F) with the temperature controller. Monitor the temperature at the auxiliary thermocouple hole at periodic intervals with a precision potentiometer. Operate the cell continuously at this temperature for 1 week (168 h).
11.4 Terminating the Test - At the end of the test period, turn off the heater and allow the cell to cool to room temperature before disassembly. Release pressure, remove the fill plug, and pour or siphon out the test coolant.
11.5 After disassembly, clean the cell with a large bristle brush rotated by an electric drill motor, pumice powder, detergent, and water.
12. Cleaning of Aluminum Test Specimen
12.1 Wash the specimen with a soft bristle brush using a mild detergent. Remove any O-ring residue by gentle scraping with a material that is softer than the aluminum (for example, a thick piece of polyethylene or polypropylene with a freshly sheared edge).
12.2 In a fume hood, immerse the specimen for exactly 10 min in an aqueous solution containing 4 parts concentrated nitric acid (70 % by weight) plus one part water at 25°C (77°F). Occasionally brush the surface with a soft bristle brush. After 10 min, transfer the beaker containing the aluminum specimen and cleaning solution to an ultrasonic cleaning unit. Apply power for 1 min. (Warning - Nitric acid is a strong oxidant. Avoid contact with skin, eyes, and clothing. Do not breathe vapor.)
12.3 Remove the specimen from the cleaning solution, flush well with tap water, then with distilled or deionized water, and finally with acetone. Make sure thermocouple holes are flushed well and excess liquid is removed. Inspect the surface using a microscope with a magnification range from 10 to 30x. If any deposits remain, repeat 12.2 and 12.3.
12.4 Dry the specimen in a vacuum oven using the same procedure and precautions in accordance with 10.4.
12.5 Cool the specimen to room temperature in a desiccator and weigh to the nearest 0.1 mg.
NOTE 1 - This cleaning procedure replaces one using chromic acid, a recognized health hazard. The qualification of this cleaning method was completed by a D15.09 Task Group and is available as Research Report.
13. Determination of Blank Correction
13.1 Clean and weigh at least 3 unused specimens in accordance with 12.1 - 12.5.
13.2 Use the average weight loss as the blank correction, provided the deviations are not significant.
14. Calculation
14.1 Calculate the heat-transfer corrosion rate (R) as follows:
R = [(Wb - Wa + B) x 1000]/A
where:
R = corrosion rate, mg/cm2/week,
Wb = weight of test specimen before test, g,
Wa = weight of test specimen after test, g,
B = weight loss of blank, g, and
A = heat-flux surface area inside O-ring, cm2.
