Setup Parameters

Here is the Critical Pitting Temperature Setup dialog box with its default parameters:

Applied E

The potential used to polarize the specimen. The allowed range is ±10 V with a resolution of 0.125 mV.

Start Temp.

The temperature at which the experiment takes the first set of data. The default range is 0°C to 200°C in 0.1° increments.

Final Temp.

The temperature at which the experiment takes the last set of data. If the current has not exceeded the limit at this or any previous temperature, the experiment ends. The default range is 0°C to 200°C in 0.1° increments.

Temp. Step

The increment by which the temperature increases after completing each scan. The minimum step value is 0.1°C. Not all controllers may support this fine a resolution.

Run Duration

This defines the maximum length of time for data-acquisition at each temperature. If the current has not exceeded the Limit I by this time during data-acquisition, the system terminates data-acquisition at this temperature and cycles to the next temperature.

Sample Period

The time between data points. The smallest sample period is 0.2 second. In pitting experiments we recommend sampling periods between 0.5 and 1 second. The sampling period, along with the Run Duration, determines the number of data points in a curve. You can calculate the number of points from:

Number of Points = Run Duration / Sample Period

The current-versus-time curves from all temperatures are stored in one data file. With ten or more curves recorded in a single experiment, the data file can become very large. Keep the data file size manageable by recording fewer curves or making the curves contain fewer data points.

Limit I

The current density at which you are satisfied that the specimen is pitting. If at any point during a scan the current density exceeds this limit, the experiment stops.

Delay Time

The Init. Delay phase of the experiment is used to allow the open-circuit voltage of the sample to stabilize prior to the start of the experiment. There is a separate Init. Delay at each temperature. The Delay Time is the time that the sample is held at open-circuit potential prior to data-acquisition. The open-circuit potential at each temperature is measured at the end of the Init. Delay. The units for the Delay Time are seconds. The minimum time is one second, the maximum time is 400 000 seconds (more than 4 days). Below 1000 seconds, the time resolution is one second. Between 1000 seconds and 10 000 seconds, it is 10 seconds. Above 10 000 seconds, it is 100 seconds.