What is the main principle of cathodic protection in concrete?

It lowers the electrochemical potential of the reinforcing steel by making it the cathode of an electrochemical cell, thus suppressing the corrosion process to a negligible rate.

What are the two main types of cathodic protection systems described?

Sacrificial Anode Cathodic Protection (SACP) which uses a more active metal (like zinc), and Impressed Current Cathodic Protection (ICCP) which uses an external DC power source and inert anodes.

What is the '100 mV decay' criterion used for?

It's a key performance test to confirm effective protection. After the system is temporarily switched off, the steel's potential should decay (become less negative) by at least 100 mV over 4-24 hours (Clause 6.3.2).

Can cathodic protection be applied to prestressed concrete?

Yes, but with extreme caution. The potential of the steel must be carefully controlled to stay above -1100 mV vs CSE to avoid the risk of hydrogen embrittlement in high-strength prestressing steel (Clause 6.2).

IS 12118 Part 2

: 1991

Protection of Structures Against Corrosion by Cathodic Protection - Application to Steel in Concrete

CurrentSpecializedCode of PracticeBIMMaterials Science · Coastal and Marine Engineering

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This standard provides guidelines for applying cathodic protection to steel reinforcement in concrete structures. It covers the principles, design criteria, system design (both sacrificial and impressed current), installation, and monitoring to mitigate corrosion, particularly in aggressive environments like marine zones.

Provides specific guidance for applying cathodic protection to steel reinforcement in concrete structures, particularly in corrosive environments.

Quick Reference Values

Minimum protective potential of steel vs CSE (Copper-Sulfate Electrode)-850 mV

Minimum protective potential of steel vs Ag/AgCl/seawater-780 mV

Maximum permissible negative potential to avoid hydrogen embrittlement-1100 mV

Minimum potential decay (depolarization) criterion over 4-24 hours100 mV

Typical current density for protection (passive steel)0.2 to 2.0 mA/m²

Typical current density for protection (corroding steel)2.0 to 20 mA/m²

Practical Notes

Ensuring electrical continuity of all reinforcement bars to be protected is a critical prerequisite for the system's success and must be verified before concreting.

The choice between a Sacrificial Anode (SACP) and an Impressed Current (ICCP) system depends heavily on the structure's size, environment, design life, and accessibility for maintenance.

Careful placement of reference electrodes is essential for accurate monitoring and control of the protection system over its service life.