Cathodic Protection (RP-B401) Calculator v1

Price: £23.10 (£23.10 Inc. VAT)
Cathodic protection calculator


Cathodic protection is widely used for the passive protection of carbon steel ship hulls, submerged structures and pipelines; i.e. it stops corrosion of the carbon steel (cathode). But it can be and is used for the protection of any metal, as long as it is electrically dissimilar to its donor (anode) and immersed in an electrolyte.

The anode eventually wastes away and must be replaced if protection is to continue. Too large an anode and the cathode will suffer from hydrogen embrittlement, too little and the anode will rapidly disintegrate. It is therefore important to ensure that anodes are correctly sized and dispersed.

Whilst the cathodic protection of carbon steel has been successfully addressed by many official and unofficial authorities and a great deal of reliable documentation has been generated covering its design and use, DnV’s RP B401 is currently regarded as the most respected. It is for this reason that CalQlata has based its cathodic protection calculator on RP B401


CathPro calculates the anodic requirements for the cathodic protection of an area of carbon steel designated for protection whilst submerged in seawater or buried in seabed sediments using aluminium or zinc anodes according to DnV’s RP B401 (October 2010)

CathPro includes calculation options for four anode types; Flush Mounted, Segment Bracelet, Half-Shell Bracelet and Slender Stand-Off

Whilst the cathodic protection calculator is limited to the above materials, it provides all the variables used in the recommended practice in a form that can be modified, if the user feels sufficiently confident to do so, thereby enabling CathPro to calculate for any pair of metals.

Note: This calculator has not been officially endorsed by DnV. It is CalQlata’s interpretation of the recommended practice

For help using this calculator see Technical Help

The cathodic protection calculator includes the following calculation options

Anode Types

Slender Stand-Off, Mounted Flush, Half-Shell Bracelet, Segmented Bracelet


Pipeline, [steel] Structure, [reinforced] Concrete

Anode Materials

Aluminium, Zinc

All of which require with the same input data and provide the same output data as follows:

You enter: and the cathodic protection calculator will provide:
  • Design life
  • Protected area
  • Anode mass
  • Anode radius
  • Anode length
  • Coat category
  • Water depth
  • Environmental temperature
  • Number of anodes
  • Total capacity
  • Initial demand
  • Average demand
  • Final demand
  • Initial anode capacity
  • Average anode capacity
  • Final anode capacity
  • Initial current output
  • Final current output
  • Initial current density
  • Average current density
  • Final current density
  • Initial coating breakdown factor
  • average coating breakdown factor
  • Final coating breakdown factor
  • Initial anode resistance
  • Final anode resistance
  • Environment resistivity
  • Compliance Checks (§7.8.4)
  • Initial: Output vs Demand
  • Capacity vs Demand
  • Final: Output vs Demand

CathPro offers the option to alter the constants recommended by RP-B401 using its Data File

Check minimum system requirements

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