Copper corrosion tester is a key equipment used to evaluate the corrosiveness of petroleum products (such as gasoline, diesel, lubricating oil, etc.) to metal materials. Its operation must strictly follow standardized procedures to ensure the accuracy of test results. The following is a detailed description from four aspects: preliminary preparation, testing steps, data analysis, and maintenance:
1、 Preparation work before operation
Sample collection and pretreatment
Sampling standard: Collect representative samples according to GB/T 4756 or ASTM D4057 requirements, avoiding the mixing of moisture, impurities, or volatile components.
Water removal treatment: If the sample contains free water, it needs to be separated by centrifugation (speed ≥ 3000rpm, time 5min) and the upper clear liquid should be taken for later use.
Preparation and activation of copper sheets
Material selection: Use electrolytic copper sheets with a purity of ≥ 99.9% (usually 25mm × 25mm × 3mm in size), with a surface roughness Ra ≤ 0.8 μ m.
Polishing treatment: Use silicon carbide sandpaper with a particle size of W20 (about 20 μ m) for rough grinding and then W0.5 (about 0.5 μ m) alumina micro powder for fine polishing until a mirror like luster is achieved.
Cleaning and degreasing: Soak in acetone and anhydrous ethanol for ultrasonic cleaning for 2 minutes each, blow dry with nitrogen, and store in a dryer for later use.
Instrument status confirmation
Temperature control system verification: Use a certified standard thermometer (accuracy ± 0.1 ℃) to verify that the actual temperature of the constant temperature bath deviates from the set value by ≤± 1 ℃.
Timing function test: Check if the timer error is less than ± 30s/h, and reset the program if necessary.
Safety protection inspection: Confirm that the exhaust volume of the fume hood is ≥ 15m ³/min, and the emergency stop button responds sensitively.
2、 Implementation of core testing process
Clamp the sample
Positioning requirement: Place the processed copper sheet flat at the bottom of a glass test tube, pour 50mL of the oil sample to be tested into the copper sheet to avoid bubbles.
Sealing measures: The test tube mouth is covered with aluminum foil to prevent volatilization, and the matching rubber stopper needs to be boiled and desulfurized in advance.
Environmental simulation settings
Temperature control: Select the test temperature according to the standard (such as 50 ℃ for gasoline and oil, 100 ℃ for jet fuel), and control the heating rate at 1-2 ℃/min to prevent sudden stress damage to the copper sheet.
Duration: The regular testing cycle is 4h ± 10min, and special studies can extend it to 24h or even longer.
Key points of dynamic monitoring
Inspection frequency: Record the temperature fluctuation of the bath once per hour, and terminate the experiment immediately if it exceeds the tolerance.
Abnormal observation: Pay attention to whether there is layering or precipitation, and be alert to non-uniform corrosion caused by local overheating.
3、 Result determination and data processing
Remove and clean
Cooling program: After reaching the specified time, turn off the heating power and let it cool naturally to room temperature before removing the test tube.
Remove oil stains: Rinse three times with n-hexane to remove residual oil film, then shake with distilled water and neutral detergent ultrasonic waves for 5 minutes.
Final purification: Repeat the acetone ethanol cleaning process described above, dry with hot air, and place on filter paper to absorb moisture for 30 minutes.
Corrosion grade assessment
Reference standard: Refer to the color chart in Appendix A of GB/T 5096 or ASTM D130 grading standard (0-4 levels), and independently rate by two or more technical personnel to take the average value.
Microscopic assistance: For cases with fuzzy boundaries, scanning electron microscopy (SEM) can be used to observe surface morphology, and EDS energy spectrum can be used to analyze element distribution characteristics.
Report preparation elements
Basic information: indicate the sample name, batch number, testing date, execution standard number, and instrument model.
Original data attachments: Attached are temperature curve graphs, digital photos, and copies of spectral analysis reports.
4、 Equipment maintenance and troubleshooting
Typical fault response plan:
Phenomenon: Display 'Err-H' alarm code → Reason: Poor contact of thermocouple → Solution: Remove the wiring terminal, polish the oxide layer and apply conductive paste
Phenomenon: Continuously low measured temperature → Reason: Solid state relay breakdown → Solution: Replace IGBT module of the same specification and conduct load test
5、 Key precautions strengthened
Cross contamination prevention and control: The testing interval for different grades of oil products must be replaced with a complete set of test tubes and brackets, and continuous operation with the same tool is prohibited.
Personnel protection requirements: Wear nitrile gloves and goggles when handling highly corrosive media. Immediately rinse with clean water for 15 minutes after skin contact.
Compliance of waste liquid disposal: Cleaning waste liquid containing heavy metal ions shall be collected and handed over to qualified units for treatment, and direct discharge into the sewer is strictly prohibited.
Copper corrosion testing is a seemingly simple but actually sophisticated technical activity, and any oversight in the process may lead to the risk of misjudgment. It is recommended to establish a three-level review system - operator self inspection, team leader review, and supervisor final review, and to keep each experiment sample sealed for at least three months for future reference. Regularly participate in CNAS accredited inter laboratory comparison activities to continuously improve testing capabilities.