Tafel Experimental Sequence
The Tafel standard technique is run by selecting Experiment > DC Corrosion > Tafel from the Framework menu bar. This initiates the following sequence of events:
- Framework creates a Runner window, and the Tafel.exp script is run in this window.
- The script creates the Setup dialog box and accepts changes in the Setup parameters.
- The script now obtains the use of the potentiostat specified during Setup and opens the data file using the Output name. If the potentiostat is in use or the file cannot be opened, the script returns you to the Setup dialog box.
- The file header information is written to the data file. This information is written to the file prior to data-acquisition. If the experiment is aborted, the output file contains only this information. This header information includes:
- Tags identifying possible analyses
- The time and date
- List of the Setup parameters.
- The script conditions the electrode if Conditioning was specified in the Setup. Conditioning is done by applying a fixed potential for a defined time. It establishes a known surface state on the corrosion specimen. A plot of current versus time is displayed during the conditioning.
- The cell is turned off and the specimen's Eoc is measured. If an Init. Delay is turned on in the Setup, this step lasts for the time specified as the Init. Delay time, or until the potential stabilizes. If no Init. Delay is specified, this step only lasts long enough for Eoc to be measured. A plot of potential versus time is always displayed. The last measured potential is recorded as Eoc.
- The actual scan occurs. The potential of the sample is swept from the Initial E to the Final E. Current readings at fixed time intervals are taken during the sweep. The sweep is actually a staircase ramp. The sample is potentiostated at the Initial E, a delay of one sample period occurs, and a reading of the current is taken. The potential is then stepped by a few mV, a delay of one Sample Period occurs, and the next current reading is taken. Stepping the potential, delaying and acquiring data points continues until the potential equals the Final E. At each point the current range is automatically switched to the optimal range for the measured cell current. If IR Compensation has been selected, each potential is corrected for the measured IR-drop of the preceding point. A plot of log(I) vs. E is displayed during the scan.
- The data are written to the output file, and the script cleans up and halts.
- When the scan is over, the cell is turned off.
- The acquired data are written to the output file.
- The script waits for you to click the F2-Skip button. When you do, the script closes everything that is open, including the Runner window.