High-silicon cast iron anodes are the most common impressed current anodes for buried installations. Their high silicon and chromium content greatly increases corrosion resistance and can ensure long-term protection of the installation.
Coke backfill is normally used to improve current output, or the anodes are installed in canisters containing carbonaceous backfill. Compared with newer types such as MMO, these anodes are recommended for dry environments where they have demonstrated better long-term performance.
Borna Electronic canistered high-silicon cast iron anodes
Known by the trade name Tantiron, the alloy is produced to ASTM A518 and IPS-M-TP-750. Its disadvantages include high weight and impact sensitivity or brittleness.
Chemical Composition of High Silicon Cast Iron Anodes to ASTM A518
| Element (Wt%) | Chemical composition | ||
| Grade 1 | Grade 2 | Grade 3 | |
| Carbon | 0.65-1.10 | 0.75-1.15 | 0.70-1.10 |
| Manganese | 1.50 Max. | 1.50 Max. | 1.50 Max. |
| Silicon | 14.20-14.75 | 14.20-14.75 | 14.20-14.75 |
| Chromium | 0.50 Max. | 3.25-5.00 | 3.25-5.00 |
| Molybdenum | 0.50 Max. | 0.40-0.60 | 0.20 Max. |
| Copper | 0.50 Max. | 0.50 Max. | 0.50 Max. |
Physical Properties of High Silicon Cast Iron Anodes to IPS-M-TP-750
| Properties | Value |
| Density | 7 – 7.05 g/cm³ |
| Hardness | Minimum 500 HB |
| Compressive strength | Minimum 650 MPa |
| Electrical resistivity | Maximum 72 μΩ·cm |
| Impact resistance | Minimum 0.1 J |
Lead caulking joins the copper cable to the anode, providing a strong connection with minimal voltage drop. Epoxy resin covers the joint, and a heat-shrink cap prevents moisture ingress.
Heat-shrink caps used on Borna Electronic high-silicon cast iron anodes
Common anode sizes, length × diameter, are 60 × 2 and 60 × 3 inches. For a 25-year design life in coke backfill, output is approximately 2 A for the 60 × 2 anode and 3 A for the 60 × 3 anode.
Maximum Current Density and Consumption of High Silicon Cast Iron Anodes by Environment
| Environmental conditions | Maximum output current density(A/m2) | Consumption rate(kg/A.Year) |
| Carbonaceous backfill | 15 | 0.10 |
| Fresh water | 10 | 0.12 |
| Sea water | 15 | 0.30 |
High Silicon Cast Iron Anode Dimensions and Weight to IPS-M-TP-750
| Anode diameter(mm) | Anode head diameter(mm) | Length(mm) | Weight(kg) |
| 51 | 76 | 915 | 14.5 |
| 51 | 76 | 1220 | 19 |
| 51 | 76 | 1525 | 22.5 |
| 76 | 102 | 915 | 29 |
| 76 | 102 | 1220 | 38 |
| 76 | 102 | 1525 | 49 |
Borna Electronic can design and manufacture high-silicon cast iron anodes to meet customer requirements or project needs.