Calculator Inputs
Example Data Table
| Case | Method | Key Inputs | Calculated icorr | Estimated Corrosion Rate |
|---|---|---|---|---|
| Example 1 | Direct | 250 µA current, 2.5 cm² area | 100 µA/cm² | 1.16 mm/y (EW 27.92, density 7.86) |
| Example 2 | Stern-Geary | βa 120, βc 100 mV/dec, Rp 250 Ω·cm² | 94.9 µA/cm² | 1.10 mm/y (EW 27.92, density 7.86) |
| Example 3 | Direct | 0.85 mA current, 10 cm² area | 85 µA/cm² | 0.98 mm/y (EW 27.92, density 7.86) |
| Example 4 | Stern-Geary | βa 140, βc 110 mV/dec, Rp 480 Ω·cm² | 53.5 µA/cm² | 0.62 mm/y (EW 27.92, density 7.86) |
Formula Used
Direct current-density method
icorr = Icorr / A
icorr is corrosion current density, Icorr is corrosion current, and A is exposed area.
Stern-Geary method
B = (βa × βc) / [2.303 × (βa + βc)]
icorr = B / Rp
βa and βc are anodic and cathodic Tafel slopes, B is the Stern-Geary constant, and Rp is polarization resistance.
Corrosion rate conversions
Corrosion Rate (mm/y) = 0.00327 × icorr(µA/cm²) × EW / ρ
Corrosion Rate (mpy) = 0.129 × icorr(µA/cm²) × EW / ρ
EW is equivalent weight and ρ is density in g/cm³.
How to Use This Calculator
- Choose the calculation method. Use direct mode when measured corrosion current is already known.
- Enter exposed area and select the correct area unit for the sample surface.
- For direct mode, enter corrosion current and select its unit.
- For Stern-Geary mode, enter anodic slope, cathodic slope, and polarization resistance.
- Add equivalent weight and density to estimate material loss rate.
- Submit the form to view results above the form, inspect the chart, and export CSV or PDF files.
Frequently Asked Questions
1. What does corrosion current density represent?
It expresses corrosion current per unit exposed area. This makes electrochemical corrosion results easier to compare across different specimen sizes, coatings, and testing conditions.
2. Why is exposed area important?
Area normalizes total current into current density. A larger sample may produce more total current, but its corrosion severity can still be lower after dividing by exposed area.
3. When should I use the Stern-Geary method?
Use it when polarization resistance and Tafel slopes are available from electrochemical testing. It is helpful when direct corrosion current is not measured explicitly.
4. What units are best for reporting icorr?
µA/cm² is often the most practical reporting unit because it is readable and common in corrosion literature. This calculator also shows A/cm², mA/cm², and nA/cm².
5. How is corrosion rate estimated from current density?
The calculator uses standard conversion equations based on current density, equivalent weight, and density. These give thickness-loss estimates such as mm/y and mpy.
6. Can I compare different materials with this tool?
Yes. Enter the proper equivalent weight and density for each material. That allows corrosion-rate estimates to reflect the specific alloy or metal being evaluated.
7. What causes very high current-density values?
Small exposed area, high measured current, low polarization resistance, aggressive electrolytes, or unstable test conditions can all drive the calculated value upward.
8. Are the exported CSV and PDF files suitable for reports?
They are useful for quick reporting, recordkeeping, and sharing calculated outputs. For formal lab reports, verify assumptions, units, and material constants before submission.