Source: https://guthlabs.ai/docs/instruments/galvanic-corrosion-series-lookup/mechanism/

instrument mechanism / verified-clean

# Galvanic / Corrosion Series Lookup mechanism

The inspectable method record for Galvanic / Corrosion Series Lookup, kept separate from implementation and qualification.

Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**

## Model scope

The supplied honest label is appropriate, but the instrument remains NEEDS_REVIEW because the exact galvanic-series source convention and the corrosion-risk flag threshold are unspecified. The four vectors use representative point values solely to verify ranking arithmetic; the implementation should expose the source table, material condition, reference electrode, and electrolyte conditions, and should return 'indeterminate' when table ranges overlap.

- Ranking metals by galvanic-series potential is appropriate for identifying the relatively more noble and more anodic member when the metals are electrically coupled in the stated electrolyte.

- The anodic metal is the one with the more negative galvanic potential under the same reference-electrode convention; this direction should be stated explicitly in the instrument algorithm.

- Potential separation is only a qualitative corrosion-risk indicator. The specification provides no defined threshold for converting separation into the required corrosion-risk flag, so the flag is ambiguous.

- A single galvanic-series lookup is not sufficient for all alloys and conditions: active versus passive stainless steel, alloy composition, surface condition, seawater chemistry, temperature, oxygenation, flow, and polarization can change the ordering.

- The lookup-table convention is underspecified. The instrument must identify the exact table edition, electrode reference, electrolyte condition, temperature, and whether listed values are point values or ranges.

## Units and conventions

- Representative open-circuit galvanic potentials are treated as volts versus a saturated calomel electrode (SCE), in aerated seawater near 25 °C.

- More positive potential means relatively more noble; more negative potential means relatively more active and anodic.

- Potential separation is calculated as absolute difference in volts: |E1-E2|.

- The test risk labels are qualitative relative labels only, not universally calibrated corrosion probabilities or pass/fail limits.

- The selected table values are representative point values for the stated material condition; actual galvanic-series data may be reported as ranges.

## Inspectable vector

One of 4 source-bound review vectors:

````
{
  "inputs": {
    "metal_1": "Zinc",
    "metal_2": "Copper",
    "electrolyte": "aerated seawater",
    "temperature_C": 25
  },
  "expected_outputs": {
    "relative_position": {
      "zinc": "more active / less noble",
      "copper": "more noble"
    },
    "potential_separation_V": 0.83,
    "anodic_sacrificial_metal": "zinc",
    "corrosion_risk_flag": "high qualitative galvanic separation; zinc is expected to corrode preferentially when coupled"
  },
  "reference_data": {
    "zinc_galvanic_potential_V_vs_SCE": -1.03,
    "copper_galvanic_potential_V_vs_SCE": -0.2,
    "source_convention": "widely tabulated standard galvanic-series values for aerated seawater near 25 °C, representative point values; ASM Handbook / MIL-STD-889 convention"
  },
  "working": "Zinc: E = -1.03 V vs SCE. Copper: E = -0.20 V vs SCE. Separation = |-1.03 - (-0.20)| = |-0.83| = 0.83 V. Since -1.03 V is more negative than -0.20 V, zinc is the anodic sacrificial metal and copper is more noble."
}
````

## Failure boundary

**BREAK_CLAIMED** · SELF_FLAGGED

The specification does not provide an actual galvanic-series table, a numerical risk threshold, or a signed-potential convention. Therefore exact lookup potentials and the corrosion-risk flag are not uniquely determined from the specification alone. A further implementation hazard is that reversing metal input order could incorrectly reverse the physical anodic/cathodic result if signed separation is treated as directional rather than using the lower-potential metal as anodic.

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/galvanic-corrosion-series-lookup/>)[03**Implementation**](<https://guthlabs.ai/docs/instruments/galvanic-corrosion-series-lookup/implementation/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/galvanic-corrosion-series-lookup/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche7/tranche7-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`