Magnesium Anode
Sacrificial magnesium anodes for buried pipelines, tanks and well casings — standard AZ63B and high-potential M1C grades, bare or pre-packaged with backfill.
Magnesium has the most negative potential of the sacrificial alloys, giving the high driving voltage needed in high-resistivity electrolytes such as soil and freshwater. It is the standard galvanic choice for buried pipelines and tanks; the trade-off is lower efficiency and faster consumption, so anode mass is sized accordingly.
- Most negative potential — highest driving voltage
- Drives current in high-resistivity soil & freshwater
- Standard (AZ63B) and high-potential (M1C) grades
- Supplied bare or pre-packaged with backfill
- Rapid polarisation of poorly-coated structures
- The default galvanic choice for buried assets
Applications: buried & onshore pipelines, underground storage tanks, well casings, electricity transmission towers, freshwater immersed structures
Documentation
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Applicable standards
Electrochemical Properties by Grade
- Parameter
- Design capacity
- Standard (AZ63B)
- ~ 1100 Ah/kg
- High-Potential (M1C)
- ~ 1230 Ah/kg
- Parameter
- Current efficiency
- Standard (AZ63B)
- ~ 50 %
- High-Potential (M1C)
- ~ 55 %
- Parameter
- Open-circuit potential (CSE)
- Standard (AZ63B)
- −1.55 V
- High-Potential (M1C)
- −1.70 to −1.75 V
- Parameter
- Closed-circuit potential (CSE)
- Standard (AZ63B)
- −1.50 to −1.55 V
- High-Potential (M1C)
- ~ −1.70 V
Typical values to ASTM B843. Standard (AZ63B) suits normal soil and freshwater; high-potential (M1C) suits high-resistivity soil or rapid polarisation.
Chemical Composition (% by weight)
- Element
- Aluminium
- Standard AZ63B
- 5.3–6.7
- High-Potential M1C
- ≤ 0.01
- Element
- Zinc
- Standard AZ63B
- 2.5–3.5
- High-Potential M1C
- —
- Element
- Manganese
- Standard AZ63B
- ≥ 0.15
- High-Potential M1C
- 0.50–1.30
- Element
- Copper (max)
- Standard AZ63B
- 0.02
- High-Potential M1C
- 0.02
- Element
- Iron (max)
- Standard AZ63B
- 0.003
- High-Potential M1C
- 0.03
- Element
- Nickel (max)
- Standard AZ63B
- 0.002
- High-Potential M1C
- 0.001
- Element
- Magnesium
- Standard AZ63B
- remainder
- High-Potential M1C
- remainder
To ASTM B843.
Pre-Packaged for Soil Service
For soil service, magnesium anodes are commonly supplied pre-packaged — the anode sealed in a cotton bag of gypsum-bentonite-sodium-sulphate backfill with the cable attached. The backfill lowers anode-to-soil resistance, keeps the surface active and retains moisture, giving a ready-to-bury, low-resistance package — used for buried pipelines, tanks and well casings, especially in higher-resistivity soils.
- Anode sealed in cotton bag of gypsum-bentonite-sodium-sulphate backfill
- Lower anode-to-soil resistance — ready to bury
- Backfill keeps the anode active and retains moisture
- Cable attached for connection to the structure
Applications: buried pipelines, underground tanks, well casings in higher-resistivity soils
Available Forms
D-Shape (Packaged) Anode
Buried pipelines · soil
D-section anode supplied pre-packaged in backfill for direct burial. The standard soil form, sized to the structure and soil resistivity.
Cylindrical / Rod Anode
Tanks · well casings
Cylindrical anodes for compact or confined installations such as tank interiors and well casings, with a lead cable for connection.
Ribbon Anode
Congested / shielded areas
Continuous magnesium ribbon for close-interval protection in congested rights-of-way or electrically shielded sections.
Elongated Anode
Long buried structures
Extended bar forms for longer buried structures where higher output per anode is required, with cast-in core and cable.
Forms shown are the most common configurations only. Most products are made to customer drawings and project specifications; additional configurations are available on request.
Frequently Asked Questions
What is a magnesium anode?
A magnesium anode is a sacrificial (galvanic) anode cast from a magnesium alloy and connected to a buried or immersed steel structure. Magnesium has the most negative potential of the sacrificial alloys, so it corrodes preferentially and drives a protective current onto the steel with no external power. It is the standard galvanic choice for buried pipelines, tanks and well casings in soil and freshwater.
Standard (AZ63B) or high-potential (M1C) magnesium anode — which do I need?
Standard AZ63B suits normal soil and freshwater. High-potential M1C has a more negative potential (about −1.70 to −1.75 V CSE) to drive current in high-resistivity soil or to polarise a poorly-coated structure quickly. Verify the driving voltage against the soil resistivity — send us the soil data and we will advise the grade.
Magnesium or zinc sacrificial anode — what is the difference?
Magnesium has a much higher driving voltage, so it works in high-resistivity soil and freshwater where zinc cannot — making it the default for buried pipelines and tanks. Zinc has lower driving voltage but higher efficiency and a long service record in seawater. Choose magnesium for soil and freshwater; choose zinc for seawater and marine service.
What is a pre-packaged magnesium anode?
For soil service the anode is supplied sealed in a cotton bag of gypsum-bentonite-sodium-sulphate backfill with the cable attached. The backfill lowers the anode-to-soil resistance, keeps the surface active and retains moisture, giving a ready-to-bury, low-resistance package — used for buried pipelines, tanks and well casings, especially in higher-resistivity soils.
Can you help size the magnesium anodes, and how many will I need?
We do not carry out the corrosion-engineering design ourselves, but for straightforward requirements our international manufacturing partners can assist with anode sizing. Send the structure dimensions, soil resistivity, coating condition, design life and required current, and we will return anode mass, grade and quantity with a quotation.
How do I get a magnesium anode price or quotation in Thailand?
PCX supplies magnesium anodes across Thailand — standard AZ63B and high-potential M1C, bare or pre-packaged, in D-shape, rod, ribbon and elongated forms. Send us the grade, anode mass or size, form and quantity — or your structure and soil data — and we will return a price. Larger quantities for installation contractors are quoted at project pricing.
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