Cathodic Protection
Cathodic Protection
Zery Engineering Company Ltd offers design, consultancy and installation services for Cathodic Protection of Pipelines and Vessels in oil and gas exploration and production.
Our Cathodic Protection Services
Protecting submerged and buried steel assets from corrosion across pipelines, vessels, and offshore installations.
Pipeline Protection
Design and installation of CP systems for buried and submerged pipelines in oil and gas production environments.
Vessels & Structures
Corrosion protection for storage vessels, tanks, and steel structures exposed to seawater or damp soil electrolytes.
Offshore Installations
CP solutions for steel-jacket and concrete platforms, including well risers and guide-tube structures.
Design & Consultancy
Engineering design to AMPP standards, including polarized potential targets of −0.85V vs. Cu/CuSO₄.
Why Steel Corrodes
Steel contains iron and iron carbide (Fe₃C). In seawater or damp soil these form countless tiny electrochemical cells — pure iron acts as the anode and iron carbide as the cathode.
Iron ions leave the anodic areas into the electrolyte, creating corrosion pits. Over time this appears as general corrosion of the structure or pipe. Coatings slow the process but wear off; marine growth alone cannot be relied upon.
Make All Areas Cathodic
Corrosion stops when current leaving the steel is reversed — so every submerged or buried metal surface receives current instead of giving it out.
Independent electrodes placed near the structure force protective current into the metal, making all areas cathodic. Two proven methods deliver this: sacrificial anodes and impressed-current systems.
Protection Methods
Either method may be applied on offshore installations — steel-jacket or concrete platforms.
Sacrificial Anode System
More reactive metals (e.g. zinc) are connected to the structure and naturally corrode in place of the steel — supplying protective current without an external power source.
Impressed-Current System
An external DC power source drives current from dedicated anodes into the structure, allowing precise control of output for larger or higher-demand assets.
Sacrificial Anode Design Guideline
A practical seven-step approach for calculating anode requirements for your application.
Calculate Area
Determine the total steel surface area to be protected (m²).
Polarized Potential
AMPP RP-01-69: target −0.85V vs. Cu-saturated CuSO₄. Select current density to achieve this.
Current Demand
Multiply required current density by area. Demand varies with the exposure environment.
Anode Mass
Use tabulated consumption rates to find the total sacrificial anode mass required.
Anode Quantity
Divide total mass into anodes sized for uniform current distribution over the area.
Anode Resistance
Calculate resistance (R) from the anode distribution and quantity.
Design Output Current
I = V / R. Output current must meet or exceed the demand from step C.
Sample Calculation — Ship Hull
Zinc sacrificial anodes · 4-year design life
Remember: distribute anodes evenly over the entire protected area. To convert kg → lb, multiply by 2.2. Always verify design output current (I = V/R) meets or exceeds the calculated demand.