03 / CATHODIC PROTECTION · SACRIFICIAL ANODE
Aluminium Anode
Aluminium-zinc-indium (Al-Zn-In) sacrificial anodes for offshore and marine cathodic protection — the highest current capacity per unit weight of the sacrificial alloys.
ALUMINIUM SACRIFICIAL ANODE
Aluminium Anodes
Aluminium-zinc-indium (Al-Zn-In) is the primary alloy for offshore and marine cathodic protection. Its low density delivers the highest current capacity per unit weight of the sacrificial alloys, while zinc and indium additions keep the surface active and prevent passivation in seawater and saline mud. อะลูมิเนียมแอโนด (aluminium anode) ใช้ป้องกันการกัดกร่อนของแท่นขุดเจาะ ท่อใต้ทะเล และโครงสร้างในน้ำทะเล.
- Highest current capacity per unit weight
- Lightweight — low structural load and drag
- Indium activation prevents passivation in seawater
- High, stable current efficiency over long periods
- Excellent utilisation for economical anode mass
- Proven for immersed and saline-mud service
Applications: offshore platforms & jackets, subsea pipelines, jetties & harbour structures, ship ballast & cargo tanks, storage-tank internals, saline-mud / seabed service
Documentation
Catalogs and technical documentation are available upon request. Please contact our team for product information, specifications, and documentation.
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Applicable standards
ELECTROCHEMICAL PROPERTIES
Electrochemical Properties
| Parameter | Typical value |
|---|---|
| Alloy basis | Aluminium-Zinc-Indium (Al-Zn-In) |
| Design electrochemical capacity | 2000 Ah/kg |
| Tested capacity (typical) | 2400–2700 Ah/kg |
| Closed-circuit potential | −1.05 V (Ag/AgCl) |
| Current efficiency | ~85–90 % |
| Utilisation factor | 0.85–0.90 |
Typical values to DNV-RP-B401.
CHEMICAL COMPOSITION
Chemical Composition
| Element | Content (%) |
|---|---|
| Zinc (Zn) | 2.5–5.75 |
| Indium (In) | 0.015–0.040 |
| Silicon (Si) | ≤ 0.10 |
| Iron (Fe) | ≤ 0.09 |
| Copper (Cu) | ≤ 0.003 |
| Cadmium (Cd) | ≤ 0.002 |
| Others (each) | ≤ 0.02 |
| Aluminium (Al) | remainder |
Typical Al-Zn-In composition to DNV-RP-B401.
AVAILABLE FORMS
Available Forms
Stand-off Anode
Offshore platforms · jackets
Cast on a steel insert and mounted clear of the structure on brackets — the standard form for large submerged structures.
Flush-Mounted Anode
Ship hulls · appendages
Mounted close to the surface where a low profile is needed, such as on hulls and appendages — reducing drag.
Bracelet Anode
Subsea pipelines
Half-shell segments clamped around a pipeline, distributing protection evenly without interrupting the line.
Tank / Elongated Anode
Tank internals · ballast tanks
Elongated forms for the internal protection of storage and ballast tanks, sized to the tank and service period.
Aluminium suits low-resistivity electrolytes — seawater, brackish water and saline mud — where the life-to-weight ratio matters; for high-resistivity soil, magnesium is used instead. Most products are made to customer drawings and project specifications.
Frequently Asked Questions
What is an aluminium (Al-Zn-In) sacrificial anode?
An aluminium anode is a galvanic anode cast from an aluminium-zinc-indium alloy. It corrodes preferentially to protect steel with no external power. The zinc and indium additions keep the surface active and prevent passivation in seawater, and the low density gives the highest current capacity per unit weight of the sacrificial alloys — making it the primary choice for offshore and marine service.
Aluminium or zinc anode for seawater — which is better?
Both work in seawater. Aluminium (Al-Zn-In) gives more current capacity per unit weight, so it is lighter for the same design life and is the standard for offshore platforms, subsea pipelines and ballast tanks. Zinc has a longer, well-understood service record and is often preferred for ship hulls, but is heavier and has a service-temperature limit. For soil and freshwater, use magnesium instead.
Which forms of aluminium anode are available?
Stand-off anodes for offshore platforms and jackets, flush-mounted anodes for ship hulls and appendages, bracelet anodes for subsea pipelines, and elongated tank anodes for storage and ballast tank internals. Most anodes are cast to customer drawings and project specification.
To which standards are the anodes supplied?
Aluminium anodes are supplied to recognised offshore standards including DNV-RP-B401, DNV-RP-F103, ISO 15589-2, NACE SP0176 and NORSOK M-503, with typical electrochemical capacity and composition as shown in the tables above.
Do you supply aluminium anodes in Thailand, and how do I get a quotation?
Yes. PCX supplies Al-Zn-In aluminium sacrificial anodes across Thailand, sourced from qualified international manufacturers and supplied to recognised standards and your project specification. Send us the anode form, mass or size and quantity — or your structure and environment data — and we will return a quotation.
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