ICCP vs Sacrificial Anode — Choosing a Cathodic Protection System per NACE SP0169 / ISO 15589 in Thailand

Corrosion eats steel structures in seawater, soil, and concrete every day. Cathodic Protection (CP) stops it by making the steel a "cathode" (a non-corroding pole). There are two main methods to choose correctly between: Sacrificial Anode and Impressed Current (ICCP).

This article compares the two systems, the protection criterion, the standards, and selection for real work in Thailand.

1. The Principle — Making Steel a Cathode

Both methods drive "protective current" into the structure so the steel stops releasing electrons (stops corroding) — differing in the "current source":

2. Which to Choose

flowchart TD
  A[Need Cathodic Protection] --> B{Size + current demand?}
  B -->|Small-medium / low current| C{Power + maintenance team?}
  B -->|Large / high current / long pipe| D[ICCP
rectifier + MMO anode]
  C -->|No / want simple| E[Sacrificial Anode
Zn/Al/Mg]
  C -->|Yes| F{High-resistivity soil/water?}
  F -->|High| D
  F -->|Low seawater| E
  E --> G[Measure -850 mV CSE
confirm protection]
  D --> G

• Sacrificial → ships, buoys, jetty piles, buried tanks, small-medium work, seawater (conductive), no power
• ICCP → long pipelines, large RC bridges, high-current structures, high-resistivity soil/water

3. Protection Criterion + Standards

• -850 mV (or more negative) versus Cu/CuSO₄ reference electrode (CSE), IR-drop corrected — per NACE SP0169 + ISO 15589-1
• Concrete → ISO 12696 (polarization decay ≥100 mV)
• Harbour/marine → ISO 13174, sacrificial design → DNV-RP-B401

Always measure potential with a real reference electrode — don't install and assume it works.

4. CP Selection/Design Checklist

🧮 If you have settled on sacrificial anodes, size them in the Anode Sizing Calculator. ICCP is a different calculation — it needs a transformer-rectifier design instead.

1. Estimate current demand — bare steel area + environment
2. Measure soil/water resistivity → points to sacrificial vs ICCP
3. Power + maintenance team available → required for ICCP
4. Select the anode by environment (Zn/Al seawater, Mg fresh water/soil, MMO for ICCP)
5. Place reference electrodes to verify -850 mV + keep records

We supply anodes for Cathodic Protection of all types — zinc (99.995%), aluminium (Al-Zn-In), magnesium, and concrete anodes — manufactured to ISO 9001 + DNV Type Approval, with guidance on designing sacrificial systems per NACE SP0169 / ISO 15589 / ISO 12696, and assessing whether your work suits sacrificial or should consider ICCP.

Talk to our engineering team to design corrosion protection that fits the job — call 02-096-2118 or LINE OA @sahawatt1988.

Summary

• Cathodic Protection = make steel a cathode to stop corrosion — two methods
• Sacrificial Anode (Zn/Al/Mg): no power, easy, low maintenance — small-medium/marine/no-power work
• ICCP (rectifier + MMO anode): high adjustable current, long life — large/high-current/high-resistivity work
• Criterion: -850 mV vs CSE (NACE SP0169 / ISO 15589) · concrete ISO 12696
• Choose by: size · current demand · resistivity · power/maintenance availability

The right CP system stops rust at its electrochemical root, extending steel structure life by decades.