ASTM G199-09 (2020) pdf free.Standard Guide for Electrochemical Noise Measurement.
Results are representative of the probe element (electrode). When first introduced into a system, corrosion rates ona probe element may be different from that of the structure.6.2 Noise can originate from thermal,electrical,and mechanical factors.Since the interest is only on the noise fromFaradaic processes,care should be exercised to minimize noisefrom other sources.
Probe elements by their nature are consumable. Hazard-ous situations may occur if probes are left in service forextended periods beyond their probe life. In someconfigurations, crevice corrosion can cause damage or leaks atthe interface between the element and its sealing surface thatcan cause false readings.
Electrical contact between probe elements should beavoided. In certain situations (for example，sour corrosion inthe presence of hydrogen sulfide), the corrosion products canlead to apparent electrical shorting of the probe elementsleading to erroneous readings.
The current range depends on the system beingmeasured.The wide dynamic ranges seen in passive-to-activetransitions (nA to mA) may require auto-ranging circuits.7.1.7 The bias current of the device should be within therequired accuracy of the measurement. Otherwise it may causean error in the measured current.The background noise of the device should be belowthe electrochemical current or potential noise being measured.Highimpedance reference electrode inputs may pick up extra-neous noise from the environment and shielding may berequired. An independent measurement of the backgroundnoise level should be performed.
The requirements in 7.1.1 – 7.1.8 do not include allpossible combinations of instrumentation and electrode arrangements.The instrument,cell,and analysis requirementsshould be determined by the particular test being undertaken.7.2 Test Cell—The test cell should be constructed to allowthe following items to be inserted into the solution chamber:Three identical electrodes, two of which comprise thecoupled electrodes and the third electrode acts as a reference.Alternatively, instead of the third identical electrode, a Luggin-Haber capillary with salt bridge connection for a referenceelectrode may be used.
An inlet and an outlet for air or an inert gas.A thermometer or thermocouple holder.
The test cell shall be constructed from materials thatwill not corrode，deteriorate,or otherwise contaminate thesolution. Guide G31 provides standard practice for conductingimmersion corrosion testing.One type of suitable cell is described in Reference TestMethod G5.Cells are not limited to that design. For example,a 1 L round-bottom flask can be modified for the addition ofvarious necks to permit the introduction of electrodes, gas inletand outlet tubes, and the thermometer holder. ASTM G199 pdf download.