Cathodic Protection Design Form
Enter project data below. The calculator estimates current demand, total charge, anode mass, recommended anode count, and expected service life.
Formula Used
1. Bare Area = Protected Surface Area × (Coating Breakdown ÷ 100)
2. Required Current (A) = Bare Area × Current Density × Safety Factor ÷ 1000
3. Total Charge Demand (Ah) = Required Current × 24 × 365 × Design Life
4. Required Anode Mass (kg) = Total Charge Demand ÷ (Anode Capacity × Utilization Factor as decimal)
5. Current Output Per Anode (A) = Driving Voltage ÷ Circuit Resistance
6. Anodes by Current = Ceiling(Required Current ÷ Current Output Per Anode)
7. Anodes by Mass = Ceiling(Required Anode Mass ÷ Anode Unit Mass)
8. Recommended Anodes = Maximum of Anodes by Current and Anodes by Mass
This approach combines current demand sizing and life-based mass sizing. Final field designs should still consider layout, anode spacing, resistivity, continuity, monitoring access, and governing project standards.
How to Use This Calculator
- Enter the total steel area that needs corrosion protection.
- Estimate the coating breakdown factor for the selected design period.
- Use a design current density appropriate for the steel and environment.
- Input anode capacity, utilization factor, driving voltage, and circuit resistance.
- Set a safety factor to cover aging, uncertainty, and field variation.
- Click the calculate button to display results above the form, review the graph, and export CSV or PDF if needed.
Example Data Table
| Scenario | Area (m²) | Breakdown (%) | Current Density (mA/m²) | Life (years) | Required Current (A) | Required Mass (kg) | Recommended Anodes |
|---|---|---|---|---|---|---|---|
| Pipeline Rehabilitation | 1000 | 25 | 20 | 20 | 6.00 | 1585.22 | 80 |
| Tank Base Ring | 650 | 15 | 15 | 15 | 1.68 | 333.16 | 23 |
| Foundation Steel Piles | 1200 | 30 | 18 | 20 | 7.45 | 1968.46 | 79 |
Frequently Asked Questions
1. What does this calculator estimate?
It estimates required protection current, total charge demand, anode mass, anode count, installed capacity, and expected service life for a sacrificial anode design.
2. Should I enter total area or bare area?
Enter total protected surface area. The calculator converts it to bare area by applying the coating breakdown factor you provide.
3. Why is coating breakdown important?
A small increase in exposed steel can sharply raise current demand and required anode mass. It strongly affects long-term design adequacy.
4. What is the role of current density?
Current density represents the protection demand per exposed area. It depends on environment, coating condition, metal type, and design philosophy.
5. Why can anodes by current exceed anodes by mass?
Anodes may contain enough total mass for life, yet still fail to deliver enough instantaneous current. That is why both checks are necessary.
6. Can I use this for reinforced concrete steel?
Yes, for preliminary comparison work. Still verify assumptions carefully because concrete systems often require project-specific current density and layout decisions.
7. Does the calculator replace a full design?
No. It is a practical estimating tool. Final design should also review standards, resistivity, polarization behavior, continuity, monitoring, and installation geometry.
8. When should I increase the safety factor?
Increase it when coating damage is uncertain, resistance may rise, future operating conditions are variable, or maintenance access will be difficult.