SOP-MECH-014
REV 2.2
CATHODIC PROTECTION SYSTEM
ELECTROCHEMICAL LOGIC
Sacrificial Anodes (Zinc/Aluminum) create a galvanic cell where the anode corrodes instead of the turbine runner. Without this, the runner becomes the anode and dissolves into the water.
THE 50% CONSUMPTION RULE
If an anode has lost >50% of its original mass or shows deep pitting, replace it immediately. Residual mass cannot sustain the protective current.
CONTINUITY SPECIFICATION
TARGET RESISTANCE
< 1.0 Ω
Measure from the anode surface to the turbine casing using a calibrated multimeter.
MOUNTING & CONTINUITY INTEGRITY
CRITICAL INSTALLATION STEPS
- Grind base plate to bare metal. NO PAINT under the anode.
- Use Grade 316 Stainless Steel bolts only. No carbon steel.
- Tighten until spring washers are fully flat for max contact.
CORROSION WARNING
If the interface is painted or greasy, the anode is 'Blind'—it looks okay but provides ZERO protection.
CRITICAL: High
resistance (>5Ω) = Passive Corrosion Active.
SYSTEM TROUBLESHOOTING
| OBSERVATION | DIAGNOSIS | CORRECTIVE ACTION |
|---|---|---|
| Anode looks brand new after 1 year | Passivity / No Continuity | Remove, clean base, re-test resistance. |
| Rapid wasting (< 3 months) | Stray Current Interference | Check motor grounding / Shaft grounding. |
| White chalky coating | Normal Oxidation (Working) | No action required if mass > 50%. |