GB/T 24488-2021Test method for electrochemical properties of magnesium alloys sacrificial anode (English PDF)

3.1 Closed circuit potential

In the electrolyte, the cathode is connected to the sacrificial anode; the potential of the sacrificial anode that is relative to the reference electrode, when the current is passing through.

3.2 Open circuit potential

In the electrolyte, the cathode is connected to the sacrificial anode; the potential of the sacrificial anode that is relative to the reference electrode, after the current is disconnected for 1 h.

3.3 Practical current capacity

The actually measured amount of electricity produced by consuming a unit mass of sacrificial anode. [Source: GB/T 17731-2015, 3.1]

3.4 Theoretical current capacity

The amount of electricity produced by consuming a unit mass of sacrificial anode, which is calculated according to Faraday's law. [Source: GB/T 17731-2015, 3.2]

3.5 Current efficiency

The percentages of practical current capacity and theoretical current capacity.

9.1 Test preparation

9.1.1 When using a copper coulombmeter (as shown in Figure 2), use fine abrasives (00 # or finer) to grind the coulombmeter's cathode copper wire; then, put it in an oven, dry it at 105 °C for 15 minutes, and cool it to room temperature; weigh it, and the weight shall be accurate to 0.1 mg. The anode copper sheet shall be cleaned before being put in the coulombmeter's solution, and the purity of copper wire and copper sheet shall not be less than 99.9%.

9.1.2 Wash the anode sample with water and acetone in turn; then, put it in an oven, dry it at 105 °C for 30 min, and cool it to room temperature; weigh it, and the weight shall be accurate to 0.1 mg. After the sample is cleaned with acetone, in order to avoid contamination of the sample, the sample shall be handled with gloves.

9.1.3 Buried anode sample: Use insulating tape to wrap the surface between 100 mm and 139 mm from the immersed end face of the sample, so that the immersion area of the sample is 41.2 cm².

9.1.4 Sample of the extruded magnesium anode of the water heater: Seal the immersed end face and the surface 10 mm away from it with insulating materials; wrap the surface between 113.2 mm and 142 mm from the immersed end face of the sample with insulating tape, so that the immersed area of the sample is 41.2 cm².

9.1.5 Sample of the cast magnesium anode of the water heater: Process it according to the method of "9.1.3 Buried anode sample".

9.1.6 Brush the cathode test crucible with soft plastic. If the inner surface of the cathode test crucible is completely covered by a high-resistance coating, and the required current cannot be obtained, the high-resistance coating on the surface shall be removed by sandblasting, wire brushing, or scraping.

9.2 Sample determination

9.2.1 Add the electrolyte to the cathode test crucible until the solution is about 15 mm away from the top.

9.2.2 Insert the sample into the rubber stopper and then put it in the cathode test crucible.

9.2.3 Put the anode copper sheet and cathode copper wire in the coulombmeter's solution, and the length of the copper wire immersed shall be 10 mm~50 mm.

9.2.4 The schematic diagram of the complete test circuit is shown in Figure 6. 0.75 mm² insulated stranded copper wire is used in the circuit. Each end of each wire is connected method of the closed-circuit potential in 9.2.6.

9.2.8 After the test is completed, first remove the wires on the sample; then, take the sample out of the electrolyte, and remove the rubber stopper; finally, remove the tape on the sample.

9.2.9 Put an untested sample in the cleaning solution preheated to 60 °C~80 °C, leave it in the solution for 10 minutes (or put it in the cleaning solution at room temperature for 30 minutes); then, wash it with tap water, and finally dry it in a 105 °C oven for 30 min; if the mass loss of the sample is greater than 5 mg, pour out the cleaning solution; if the mass loss of the sample is less than 5 mg, place the tested sample and the untested sample together in the cleaning solution at 60 °C~80 °C for 10 min or put them in room temperature cleaning solution for 30 min; then, wash them with tap water, and dry them in a 105 °C oven for 3 h; if the mass loss of the untested sample is more than 5 mg, repeat the steps 9.2.1~9.2.9.

9.2.10 When using a copper coulombmeter, the cathode copper wire on the coulombmeter shall be removed, then washed with tap water, and finally placed in an oven and dried at 105 °C for 30 minutes.

9.2.11 Take the sample, untested sample, and copper coulombmeter's cathode copper wire out of the oven, and cool them to room temperature; weigh them, and the weights shall be accurate to 0.1 mg.

To avoid contamination of the sample and the coulombmeter's cathode copper wire, gloves shall be worn during the weighing process.

11.1 Repeatability

In the same laboratory, according to the same test method, the same operator uses the same equipment to test the same object in a short period. The absolute differences between the two independent test results (the average value of 5 samples) obtained by conducting tests independently shall not be greater than the following values; it is premised that the situation that the absolute differences are more than the following values does not exceed 5%.

--- Actual capacitance: <=0.06 A · h/g.

--- Final closed-circuit potential: <=0.01 V.

--- Open-circuit potential: <=0.02 V.

11.2 Reproducibility

In different laboratories, according to the same test method, different operators use different equipment to test the same object independently. The absolute differences between the two independent test results (the average value of 5 samples) obtained by conducting the test independently shall not be greater than the following values; it is premised that the situation that the absolute differences are more than the following values does not exceed 5%.

--- Actual capacitance: <=0.15 A · h/g.

--- Final closed-circuit potential: <=0.05 V.

--- Open-circuit potential: <=0.08 V.