，对这个标准有比较全面的介绍
Introduction
GB 4334.9-48 is a national standard promulgated by the State Administration of Quality Supervision, Inspection and Quarantine for the measurement of corrosion potential (the open circuit potential) of stainless steels. The standard is mainly applicable to electrochemical corrosion experiments and process control of various stainless steels. The national standard uses copper-copper sulfate reference electrodes, silver chloride reference electrodes, and corrosion potential meters to measure the corrosion potential of stainless steels with a precision of 20 mV.
1 Scope
This standard specifies the test conditions and test methods for the corrosion potential measurement of stainless steels by a corrosion potential meter.
2 Principle
The stainless steel corrodes in the electrolyte and produces stainless steel ions, and then the anodic reaction and the cathodic reaction take place at the same time to form an electrochemical potential equilibration potential. Using a corrosion potential meter with a reference electrode, one end contacts the stainless steel electrode, and compares the measured potential with the known potential of the reference electrode, and finally converts the comparison results into a standard signal value.
3 Test Conditions
Test Solution: For stainless steels to be tested, the test solution should consist of 5% hydrochloric acid (or 10g/L chlorinated alum) or 10% sodium hydroxide solution or 0.01 mol/L sulfuric acid (or 0.002mol/L sodium sulfate).
Test Temperature: The test temperature should be 25±2℃.
Temperature Compensation: During the corrosion potential measurement, temperature compensation should be done according to the changes in the testing environment.
Instrument Sychronization: Before starting the measurement, the corrosion potential meter and the reference electrode should be synchronized.
4 Test Method
Instrument Setup: Put the corrosion test sample into the electrolyte stored in the test vessel with appropriate temperature, immerse the reference (copper-copper sulfate) electrode and the measurement electrode in the test solution and adjust the electrode distance to ensure that the space between them is not more than 1cm.
Connection: Put the reference equipment on the measurement instrument. Connect the copper-copper sulfate reference electrode to the A-end of the instrument, and connect the stainless steel electrode to the B-end of the instrument. If two or more measurement points are to be measured on the sample, connect the electrodes to the universal interface of the instrument in sequence.
Measurement: After the instrument is calibrated and connected correctly, select the measurement mode and calibration standard of the corrosion potential meter, adjust the parameters such as measuring time, measuring delay time, ratio, etc., and then press “Start”. The instrument will display the corrosion potential value of the stainless steel sample.
Result Record: Record the corrosion potential value obtained from the instrument and the calibration standard and the temperature of the test solution at the time of the test.
5 Result Sampling
The corrosion potential value of each organization shall be measured at least 3 times, and the result shall be the average value of 3 times of measurement.
6 Analysis and Evaluation
The measured corrosion potential value of the sample should be compared with the upper limit or lower limit in the relevant standards. In general, the measured data should be within the negative value corresponding to the upper limit of the steel grade in the standard, but for some special test processes, such as galvanizing and phosphating, the designated upper limit value may be higher.
Conclusion
The corrosion potential measurement of stainless steels is very important in the field of electrochemistry. GB 4334.9-48 is a national standard used to evaluate the corrosion of stainless steels. The article introduces the scope, principle, test conditions and test methods of the national standard in detail, and provides the resultsampling and analysis and evaluation of the results. The best way to ensure the accuracy of the test results is to accurately use the potential meter, reference electrode and related equipment, and strengthen the connection and calibration.
