DNV-RP-B401 Offshore Cathodic Protection Design Calculator

Calculate initial, mean, and final cathodic protection current demand (Amps) and total net galvanic anode mass (kg) per DNV-RP-B401 standards.

Structure Surface Area & Coating

Total Steel Surface Area A_c (m²):

Design Operating Life t_life (years):

Seawater Climatic Zone:

Coating Category (DNV):

Anode Material Alloy:

Anode Utilization Factor u: Stand-off: 0.85 - 0.90 | Flush: 0.80

CP Current & Anode Mass Requirements

Total Net Anode Mass M_tot:

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Mean Current Demand I_mean:

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Initial Polarization Current I_ini:

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Final Current Demand I_fin:

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Mean Coating Breakdown Factor (f_cm):

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Frequently Asked Questions

Why does DNV-RP-B401 require three distinct current density checks (initial, mean, final)?

Initial current is required to rapidly polarize bare steel into the immune zone (-800 mV vs Ag/AgCl) and form a protective calcareous deposit layer. Mean current governs total sacrificial anode consumption, and final current ensures repolarization at the end of life as coatings deteriorate.

What is the electrochemical capacity (ε) of aluminum-zinc-indium anodes?

High-purity Al-Zn-In alloys deliver 2,000 to 2,600 A·h/kg in natural seawater, providing more than 2.5 times the energy density of zinc (780 A·h/kg) with minimal weight burden on subsea structures.

What is the anode utilization factor u?

The utilization factor u (0.80 to 0.90) accounts for unconsumed core steel and remnant anode mass left on the bracket when the anode geometry thins and its current output drops below design threshold.