Anodes designed around the structure
Some structures need an anode designed specifically for them. Limited space, awkward geometry, restricted access or an existing protection arrangement can all rule out a standard shape.
RELI ANODES has the engineering and manufacturing capability to produce anodes to almost any approved geometry — cylindrical, spherical or entirely bespoke — in aluminium or zinc alloy.
Custom anodes are equally suited to new structures, retrofit projects and like-for-like replacement where the original design is no longer available.
What we customise
Every custom anode is defined by four inputs, agreed with you before production.
Shape
Cylindrical, spherical or any other approved geometry, developed for the application.
Dimensions
Length, diameter, thickness and overall form, manufactured to your approved drawing.
Mounting
Inserts, fixings and attachment details designed for the structure and installation conditions.
CP requirement
Alloy, net weight and configuration aligned with the approved CP design and service life.
Key features
Custom geometry
Application-specific shapes built from your drawings.
Project-specific dimensions
Sized from the CP calculation and installation space.
Installation flexibility
Mounting and connection designed for the structure.
Material options
Aluminium or zinc alloy to suit the environment.
Technical data
Typical supply parameters. Final values are confirmed against your approved drawing and CP design.
- Product
- Custom application sacrificial anode
- Protection method
- Sacrificial cathodic protection
- Typical applications
- Specialised steel structures and marine applications
- Service environment
- Seawater and marine
- Materials
- Aluminium alloy or zinc alloy, as the CP design requires
- Shapes
- Cylindrical, spherical and other custom configurations
- Dimensions
- To approved drawing and CP design
- Mounting
- To the structure and approved installation design
- Electrical connection
- As required by the approved CP design
- Installation
- Project-specific
- Design life
- As defined by the CP design
- Specification
- Applicable alloy standard, client specification and approved drawing
Materials and standards
Choose the alloy to suit the environment and CP design, then the chemistry to suit your specification.
Aluminium (Al-Zn-In)
The usual first choice offshore: 2,550–2,750 Ah/kg and low weight for long design lives.
- Galvalum III equivalent
- DNV / ISO
- Alanode
Zinc
Compact, self-regulating and well proven — often chosen for hulls and confined spaces.
- MIL-DTL-18001
- ASTM B418 Type II
Available grades
Galvalum III equivalent
A well-established Al-Zn-In chemistry for seawater service, cast to equivalent composition limits.
DNV / ISO
Al-Zn-In composition in line with the limits given in DNV-RP-B401 and ISO 15589-2.
Alanode
Aluminium alloy chemistry supplied to the applicable Alanode composition limits.
US Military spec. (MIL-DTL-18001)
Zinc alloy with controlled aluminium and cadmium additions, widely specified for seawater service.
ASTM B418 Type II
High-purity zinc with very tight iron limits, typically specified for soil and fresh-water service.
Client specification
Your own chemistry, testing and documentation requirements, reviewed and confirmed with you before production starts.
Chemical composition
Composition limits in % by weight for the chemistries we supply.
Aluminium alloys
| Element | Galvalum III (equiv.) | DNV / ISO | Alanode |
|---|---|---|---|
| Zn | 2.0 – 6.5 | 2.5 – 5.75 | 0.50 – 5.00 |
| In | 0.01 – 0.02 | 0.016 – 0.04 | 0.005 – 0.05 |
| Si | 0.08 – 0.20 | 0.12 max. | 0.10 max. |
| Fe | 0.12 max. | 0.09 max. | 0.13 max. |
| Cu | 0.006 max. | 0.003 max. | 0.01 max. |
| Cd | 0.002 max. | — | — |
| Others (each) | 0.02 max. | 0.02 max. | 0.02 max. |
| Others (total) | 0.06 max. | — | — |
| Al | Remainder | Remainder | Remainder |
Zinc alloys
| Element | US Military spec. (MIL-DTL-18001) | ASTM B418 Type II |
|---|---|---|
| Al | 0.10 – 0.50 | 0.005 max. |
| Si | 0.125 max. | — |
| Cd | 0.025 – 0.15 | 0.03 max. |
| Fe | 0.005 max. | 0.0014 max. |
| Pb | 0.006 max. | 0.003 max. |
| Cu | 0.005 max. | 0.002 max. |
| Zn | Remainder | Remainder |
Specification note
Final chemistry should always be confirmed against the applicable material specification and approved project documents before production.
Electrochemical performance
Reference characteristics for our aluminium alloy anodes.
- Test environment
- Seawater at 23 °C
- Reference electrode
- Silver / silver chloride (Ag/AgCl)
- Open-circuit potential
- More negative than −1.10 V vs Ag/AgCl
- Closed-circuit potential
- More negative than −1.05 V vs Ag/AgCl
- Electrochemical capacity
- 2,550 – 2,750 Ah/kg
Performance note
Values apply to aluminium alloy anodes in seawater at 23 °C. In-service performance also depends on alloy chemistry, temperature, current demand and anode geometry, so final design values should always come from the approved cathodic protection (CP) design.
Applications
Specialised marine structures
Structures that need a purpose-designed anode.
Offshore steel components
Components with restricted space or access.
Retrofit CP
Added protection on existing assets.
Replacement systems
Reproducing anodes where original designs are unavailable.
Seawater steel structures
Custom anodes for submerged steel.
Application-specific CP
Any system with special requirements.
Manufacturing and quality
A controlled route from your drawing to a documented, ready-to-install anode.
-
01
Engineering review
We review your drawings, CP design and specification, and confirm alloy, net weight, insert design and tolerances before production.
-
02
Insert preparation
Steel inserts are cut, formed and surface-prepared to the approved design for a secure bond with the anode.
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03
Melting and chemistry control
Each melt is prepared to the specified alloy, and its chemistry is checked against the required limits before casting.
-
04
Casting
Anodes are cast to the required shape and net weight, with the insert soundly embedded.
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05
Inspection and testing
Visual, dimensional and weight checks, plus chemical analysis and electrochemical testing where the specification requires them.
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06
Documentation and dispatch
Anodes are identified, packed for safe transport and supplied with the agreed test records.
Inspection and documentation follow the project's inspection and test plan (ITP). Read about our approach to quality.
Frequently asked questions
What are custom application anodes?
Sacrificial anodes manufactured for specialised applications where standard configurations do not meet the structural or installation requirements.
Can you manufacture custom shapes?
Yes. We produce cylindrical, spherical and other approved geometries to your requirements.
Can you work from our drawings?
Yes. Custom anodes are produced to your approved drawings, project specifications and CP design.
Which materials can be used?
Aluminium alloy or zinc alloy, depending on the environment, CP requirements and specification.
Are custom anodes suitable for retrofit?
Yes. Custom configurations are often the best solution for existing structures that need replacement or additional protection.
How are the dimensions decided?
From the approved CP design, the structure, installation conditions, required design life and project specification.
Have a special anode requirement?
Send us your drawing, dimensions, structure details or CP requirements. We'll review them and propose the right solution.
Helpful to include
- Drawing, sketch or sample photos
- Structure and installation details
- Alloy and specification
- Required net weight or CP design
- Mounting and connection requirements
- Quantity and delivery schedule
