ER Probe Corrosion Rate Calculator
Calculate metal loss and MPY from Electrical Resistance probe readings.
Start reading (T1)
End reading (T2)
2 mils (Wire Loop – High Sensitivity)
4 mils (Wire Loop)
5 mils (Tube Loop)
10 mils (Standard Tube/Strip)
20 mils (Standard Tube/Strip)
40 mils (Heavy Duty)
80 mils (Extended Life)
Total life of the sensing element
Duration between readings
Analysis Results
Change in Reading (Digits)
0
Total Metal Loss
0 mils
Corrosion Rate (MPY)
0.00 MPY
Corrosion Rate (Metric)
0.00 mm/y
Understanding ER Probe Corrosion Calculations
Electrical Resistance (ER) probes are a standard method for monitoring corrosion in industrial environments such as oil and gas pipelines, water treatment systems, and chemical processing plants. Unlike coupons which require removal for analysis, ER probes provide continuous online monitoring of metal loss.
How the Calculation Works
The ER probe operates on the principle that the electrical resistance of a metal element increases as its cross-sectional area decreases due to corrosion. The instrument typically provides a linearized reading between 0 and 1000, representing the percentage of the probe's lifespan consumed.
The core formula used in this calculator is:
Metal Loss (mils) = (Reading Change × Probe Span) / 1000
CR (MPY) = (Metal Loss × 365) / Time in Days
Key Variables Explained
- Instrument Reading (0-1000): A dimensionless number provided by the corrosion meter (e.g., Cosasco, Metal Samples). A reading of 0 indicates a new probe, while 1000 indicates the element is fully consumed.
- Probe Span: This defines the measurement range or "life" of the probe element in mils (thousandths of an inch). A standard tubular element might have a 10 or 20 mil span. Higher spans last longer but may be less sensitive to short-term changes.
- Time Elapsed: The duration between the initial and final reading. For accurate MPY (Mils Per Year) calculations, accurate time tracking is essential.
Interpreting the Results
MPY (Mils Per Year) is the standard unit for projected annual penetration rate.
- < 1 MPY: Generally considered low corrosion; excellent control.
- 1 – 5 MPY: Moderate corrosion; requires monitoring.
- > 5 MPY: High corrosion; may require immediate chemical treatment intervention or process adjustment.
Note: Negative corrosion rates usually indicate temperature fluctuations affecting the resistance readings or probe deposition (conductive scales), rather than actual metal gain.