Flexible Anode for Cathodic Protection

MMO/Ti flexible linear anodes · impressed current cathodic protection

Flexible Linear Anode for Cathodic Protection of Pipelines and Tank Bottoms

An MMO/Ti flexible anode is a continuous, cable-style anode that runs alongside the structure it protects. Instead of pushing current through a kilometer of soil from a single groundbed, it releases current evenly along its full length — so the far end of a pipeline and the center of a tank bottom get the same protection as the near end. Each meter is a Grade-1 titanium wire coated with IrO₂/Ta₂O₅ mixed metal oxide, prepacked in a conductive coke-breeze sock. Standard output is 52 mA/m with a 25-year design life; higher-output and longer-life options are available.

What makes a flexible anode different

A conventional groundbed is a point source: one anode, or a small row of anodes, pushing current across a wide area of soil. That works fine on open rights-of-way, and poorly almost everywhere else.
Flexible linear anodes were developed for exactly the cases where discrete groundbeds fall short. Because the anode is a continuous cable laid in the same trench as the pipe — or in a serpentine under a tank bottom — the current path to the steel is short and even. There are no dead zones at the far end of the line, no areas where a coating holiday sits outside the protective range, and no reliance on low-resistivity soil to carry current.

That close spacing also changes the electrical picture. With the anode sitting close to the structure, the anode-to-soil gradient stays small, which means less stray current reaching neighboring utilities and less risk of interference complaints on congested rights-of-way. On retrofits under existing tank bottoms, the cable can be installed by horizontal directional drilling without excavating the floor — something a rigid anode cannot do.

Most of our orders fall into two categories: new pipeline construction where the spec asks for distributed current, and tank-bottom or congested-network retrofits where a discrete groundbed physically cannot fit.

• • Uniform current, no dead zones

    Current discharges continuously along the cable, so coverage does not taper off at the far end the way it does with a point groundbed.

  • Close-coupled, low gradient

    Laid beside the pipe or beneath the tank, the anode keeps the current path short and the anode gradient small.

  • 25 year design life

    Rated at 25 years at maximum output, tested per NACE TM108-2012. Up to 50 years available when output is derated.

  • Low consumption rate

    Noble-metal oxide loading ≥ 8 g/m² with consumption ≤ 6 mg/A·yr — the coating, not the titanium, is the working surface.

  • Works in hard soil
    The prepacked coke breeze gives each meter its own low-resistance discharge path — no remote groundbed needed in rocky, dry or permafrost ground.

  • Kind to neighbors

    Low anode gradient means less stray current on adjacent utilities — a real advantage in congested urban rights-of-way.

  • Installs fast, on reels

    100–500 m per reel, laid by hand or trencher. No casing, no deep drilling, no backfill mixing on site.

  • Built to your CP design

    Wire diameter, output, cable type, connectors and splice kits are selected from your current-output and life requirements.

How it works in the field

The anode is one half of an impressed current system. The rectifier feeds DC to the anode, and the anode discharges it into the soil, where it travels to the protected steel and returns to the rectifier. Where the anode sits decides how evenly that current arrives.

Technical specifications

Standard values below cover most projects. Wire diameter, current output and design life are matched to your CP design before we quote.

Parameter	Standard	Custom options
Anode substrate	Grade-1 titanium wire, per ASTM B 863	Grade-2 titanium on request
Wire diameter	1.0 mm / 1.5 mm / 3.0 mm	Selected by current-output target
MMO coating	IrO₂ / Ta₂O₅ mixed metal oxide, loading ≥ 8 g/m² (6 g/m² minimum)	Coating recipe tuned for soil or seawater service
Current output	52 mA/m at 25-year design life (1.0 mm wire)	Up to 300 mA/m with 3.0 mm wire; output derated for longer life
Design life	25 years at maximum output	40–50 years with derated output
Outer diameter	38–40 mm (coke-breeze sock)	—
Backfill	Calcined coke breeze, carbon content ≥ 98.5%, prepacked in porous fabric sock	Sock material and mesh selected for your backfill
Consumption rate	≤ 6 mg/A·yr of noble-metal oxide	—
Cable / conductor	10 mm² stranded copper, HMWPE insulation	Halar or PVC insulation; 16–35 mm² conductor
Minimum bending radius	≈ 500 mm — hand-laid in trench or coil	Tighter radii per project test
Length per reel	100 m / 250 m / 500 m	Continuous lengths to 1,200 m
Reference standards	NACE TM108-2012 (performance test), ISO 15589-2 (pipeline CP), GB/T 33637-2025 (MMO/Ti flexible anode), ASTM B 863

Where flexible anodes earn their keep

Any asset where a remote groundbed cannot cover the whole structure — physically, electrically, or on the budget sheet.

1. Buried oil & gas pipelines
   Urban rights-of-way, casings, river crossings and horizontal directional drilling sections where a discrete groundbed cannot be sited.
2. Storage tank bottoms
   Aboveground tanks, new and retrofit, including serpentine layouts under secondary containment with no excavation of the floor.
3. Dense pipe networks
   Plants, terminals, compressor stations and airport apron networks where dozens of lines share a narrow corridor.
4. High-resistivity ground
   Rocky, dry, sandy or permafrost soil where a remote groundbed simply will not push current far enough.
5. Rehabilitation projects
   Repolarizing aging coated pipelines and tanks where the coating is degraded but the asset cannot be taken out of service for long.
6. Concrete & marine structures
   Conductive-polymer flexible anodes for reinforced concrete and jetty utilities, specified separately from the MMO/Ti soil type.

Export orders, done the way contractors expect

We ship to CP contractors, EPC firms and engineering houses. Every order leaves with documents your inspector will actually accept.

Frequently Asked Questions

What is a flexible anode used for?

A flexible linear anode is an impressed-current anode used in cathodic protection. It is a continuous cable laid close to the protected structure — along a buried pipeline or beneath an aboveground storage tank — that discharges protective current evenly along its full length. It is specified where discrete groundbeds cannot provide uniform coverage: congested pipe networks, tank bottoms, high-resistivity soil and retrofit projects.

What current output do you supply per meter?

Standard output is 52 mA/m on 1.0 mm wire at 25-year life. Higher outputs up to 300 mA/m are available with 1.5 mm and 3.0 mm wire, and output can be derated where a longer design life matters more.

Can it be retrofitted under an existing tank bottom?

Yes. Because the anode is a flexible cable, it can be installed beneath an operating tank by horizontal directional drilling or sleeving, without excavating the tank floor. Serpentine layouts under secondary containment are a standard retrofit configuration.