Iron-silicon anodes

Iron-silicon anodes: overview

Fe/Si anodes provide anti-corrosion protection of steel structures and pipelines by the impressed-current method. Made of high-silicon cast iron alloy, they are one of the most widely used anode materials by corrosion specialists to protect steel in the most diverse situations.

They are cast in various sizes and shapes (Ø 30 to 76 mm, length 300 to 1,525 mm, weight 2 to 50 kg), with a special head configuration available on request. Two compositions are available: Fe/Si (silicon 14.25-15.25%) and Fe/Si/Cr (with chromium 4-5% for more aggressive environments).

Typical consumption rates (Ferroline range) are about 0.11 kg/A·yr in fresh water, 0.31 to 0.47 kg/A·yr in sea water, 0.68 kg/A·yr in groundwater/sand and 0.10 kg/A·yr in carbonaceous backfill.

What role they play

An impressed current system consists of a power source, the transformer-rectifier, and a groundbed that passes the current into the soil or water. Iron-silicon anodes form that groundbed. Unlike a sacrificial anode, they do not protect by dissolving themselves: they conduct the current supplied by the rectifier while being consumed very slowly.

Fe/Si or Fe/Si/Cr?

The Fe/Si grade suits mildly aggressive soils and waters. In the most aggressive environments, the chromium grade resists better and lasts longer. The consumption rates above show the difference between environments; together with the target service life, they determine the anode mass required.

Good to know

The real service life of a groundbed depends as much on installation as on the alloy: a well-compacted carbonaceous backfill around the anodes lowers their resistance and evens out their consumption.

Iron-silicon anodes: technical specifications

Iron-silicon anodes: documentation