Example Data Table
| Area (m²) | Current (mA/m²) | Coating | Life (y) | Material | Unit Mass (kg) | Design Current (A) | Req. Mass (kg) | Qty (pcs) | Spacing (m) |
|---|---|---|---|---|---|---|---|---|---|
| 120 | 20 | 0.8 | 15 | ZINC | 10 | 1.92 | 329.79 | 33 | 1.82 |
Formula Used
How to Use This Calculator
- Enter the protected surface area and design current density.
- Set coating factor to reflect exposure and coating quality.
- Choose an anode material preset or provide custom capacity.
- Confirm utilization, efficiency, and safety factor for your project.
- Input the single anode mass to convert total mass into quantity.
- Press Calculate; then export CSV or PDF if needed.
Design Inputs That Drive Anode Count
Anode quantity starts with protected surface area and design current density. The calculator converts mA/m² to amperes using I = A × J × C ÷ 1000. For marine steelwork, designers often test scenarios between 5 and 30 mA/m², then refine values from coating surveys and environment class. Increasing area or current density raises total ampere-hours linearly across the design life.
Coating Factor and Practical Coverage
Coating factor represents how much bare metal is effectively exposed. A value of 1.00 behaves like an uncoated surface, while 0.60–0.85 suits coated assets with expected holidays and wear. For complex structures, split the job into zones with different coating factors, calculate each zone, and sum the anode quantities. This approach helps align procurement with inspection data and staged repairs.
Capacity, Efficiency, and Material Selection
Sacrificial anode mass depends on capacity (Ah/kg) and efficiency. Higher capacity reduces required mass for the same charge demand. Typical datasheets list aluminum around 2500 Ah/kg and zinc near 1200 Ah/kg, with efficiency commonly near 0.90 for quality alloys. The preset menu auto-fills these values, but you can enter vendor-specific numbers to match certification and test reports.
Utilization, Safety, and Procurement Mass
Utilization accounts for end-of-life waste where the core or insert cannot be consumed. Many designs use 0.80–0.90 depending on geometry. Safety factor, usually 1.10–1.30, covers uncertainty in current demand, temperature, salinity, and installation tolerances. The required mass is Q × SF ÷ (Cap × U × η), then converted into a whole-number quantity using the selected unit mass.
Spacing Estimates and Reporting for QA
When you provide a structure length, the calculator estimates average spacing as L ÷ N to support layout planning. Use this as a starting point, then adjust for joints, shielding, and access constraints. Export the CSV for design reviews and the PDF for submittals. Store your input set with project notes so recalculations remain traceable through inspection updates. Use these exports to standardize approvals across teams quickly.
FAQs
It scales the effective current demand. Lower coating factor means less exposed metal, so the design current and total ampere-hours drop, reducing required anode mass and quantity.
Area, current density, and design life drive charge demand directly. Doubling any of these roughly doubles total ampere-hours, which increases required anode mass and the calculated quantity.
Yes. Select “Custom” and enter the capacity and efficiency from your anode datasheet. This keeps the calculation aligned with vendor certification and test documentation.
Not all anode mass is consumable, and real electrochemical output is below theoretical. These factors prevent under-sizing by accounting for geometry losses and material performance.
No. It is an average spacing based on length and quantity. Final placement should consider shielding, current distribution, attachment points, and inspection access.
Confirm current density basis, coating survey data, material datasheets, and design life. Then review safety factor assumptions and check that unit mass matches the supplied anode type.