Magnesium vs Zinc vs Aluminum
Choose the metal by the water it sits in

By **the water the structure sits in**, not by soil: • **Magnesium** — fresh water and very brackish water. Highest driving potential, so it pushes current through high-resistivity water. The maker says it does not belong in ordinary seawater. • **Zinc** — seawater. Lowest driving potential, so overprotection that lifts paint is rare. The maker says it does not belong in brackish water. • **Aluminum (Al-Zn-In)** — seawater and brackish water. Highest capacity. The maker says it does not belong in fresh water or soil. **Sahawatthanakit supplies anodes for water immersion and concrete embedment only — buried/soil cathodic protection is out of scope.** If your job is a buried pipe or tank, tell us and we will say plainly that it is not ours.

Capacity is the current an anode can deliver per kilogram. The higher it is, the less metal you need for the same protected area. **The figures the maker publishes:** • **Aluminum** 2,481 Ah/kg (12-month free-running test) — warranted design values ≤30°C: 2,000 · 60°C: 1,500 · 80°C: 720 Ah/kg • **Zinc** 780 Ah/kg — at equal volume, aluminium gives about 21.8% more capacity • **Magnesium** ≥ 1,100 Ah/kg (High potential) or ≥ 1,105 Ah/kg (AZ63), efficiency ≥ 50% The maker publishes no theoretical capacity and no annual consumption rate, so we do not print those. Real service life depends on anode weight and the current your structure draws — send the data and we will work it out.

**As stated by the manufacturer on its own website:** • **Aluminum** — TIS 3359-2565 · DNV Type Approval (fits any DNV-classed vessel) · DNV-RP-B401 • **Zinc** — MIL-A-18001K · GL-Zn1 · production approved by DNV-GL • **Magnesium** — ASTM G-97 • **Concrete anode** — TIS 3029-2563 · ASTM B418 Type II · ISO 12696 **Documents available on request:** mill certificate + electrochemical test report. If your TOR names a different standard, send it over and we will tell you whether it matches — we will not guess on your behalf.

Four types — magnesium (condenser anode) · zinc · aluminium (Al-Zn-In) · concrete anode (zinc core in alkaline mortar). **Sizes:** the maker publishes no standard size table, so we do not advertise sizes we cannot guarantee — **quoted per drawing.** Send the size or drawing you need and we will check it with the maker and come back. **Price:** quoted per enquiry, because it depends on the actual weight and the metal price on the day. **Scope:** water immersion and concrete embedment only; buried/soil work is out of scope. Send water data + structure dimensions → type and quantity recommended within 24 hours, quotation within 48 hours.

It depends on the size of the structure and whether there is power on site: • **Sacrificial (galvanic) anode** — suits small to medium structures, needs no power supply and nobody to run it • **ICCP (impressed current)** — suits large structures, or conditions where a galvanic anode cannot deliver enough current; needs DC power, a rectifier and someone taking readings The two differ a great deal in cost and it scales with the steel surface area to be protected, so we quote per enquiry only. Send your structure dimensions and site conditions and we will cost both and show you which works out cheaper. See Galvanic vs Impressed Current.