Silicon Iron Anodes

High Silicon Cast Iron anodes are the most commonly used anodes in cathodic protection are produced in two alloy types with the principal addition of chromium. The principal reason for superior cast iron performance is the formation of a silicon oxide (Si02) film that forms on the anode surface, reducing the rate of oxidation, and retarding the consumption rate. They have good electrical properties and the resistance of the alloy is 72 micro-ohms per cubic centimeter at 20 degrees C. To be successful in soils, the anodes are backfilled with metallurgical or petroleum coke breeze to reduce the anode resistance and increase the effective anode surface area. Even when the anodes are pre-packaged in coke breeze filled canisters, filling the annular space between the canister and the soil with additional coke breeze is a recommended practice. In seawater, the anode will discharge current at very low voltages compared to graphite rods and, therefore, do not require backfill. SYNCOR developed cable-to-anode connection procedures to ensure the good and long operation of the anodes.

The anodes exhibit superior conductivity and experience very little change in resistance with time, unless the anode is damaged. The high tensile strength of the metal is an asset in some circumstances, except that their very low elongation makes them brittle and subject to fracture from severe mechanical and thermal shock.

Tubular

Cast iron anodes are manufactured in a wide variety of dimensions, shapes and weights. A proprietary type of cast iron anode, originally manufactured from “off-specification” corrosion resistance piping, is called a tubular anode. This utilizes the ASTM 518 Grade 2 chromium alloy to have superior resistance to “end effect”, common to anodes with poor connection resistance values.

Typical Applications

• Horizontal Groundbeds
• Deepwell / Open hole Groundbeds
• Anode Strings
• Internal Plant Protection
• Offshore/Marine Structures
• Seawater intakes

Features

Chemical Composition ASTM-518

For CP design a current density of not more than 30A/m2 for sea and 10A/m2 for soil of anode surface is recommended
Centre connection less than 0.001 Ohm resin encapsulated
Supported Cable: XLPE/PVC, HMWPE, PVDF/HMWPE.

Characteristics and Standard Dimensions

Backfill material

Gypsum 75%, Bentonite 20%, Sodium Sulphate 5%