When designing systems that involve multiple metals, especially in moist or marine environments, understanding the galvanic series is critical. This electrochemical ranking helps predict which metals are more likely to corrode when in contact with each other. By referencing standard electrode potentials, engineers can assess corrosion risks, select compatible materials, and implement protective measures to extend service life and ensure structural integrity.
The galvanic series (also called the electrochemical series) ranks metals based on their standard electrode potential (vs. SHE: Standard Hydrogen Electrode) in an electrolyte (e.g., seawater, acidic solution).
This determines which metal is more likely to corrode when two different metals are in electrical contact in a moist or conductive environment.
Standard Electrode Potentials of Common Metals
| Metal / Alloy | Electrode Potential (V vs SHE) | Corrosion Tendency | Notes |
| Magnesium (Mg) | -2.37 | Very Active | Common sacrificial anode material |
| Zinc (Zn) | -0.76 | Very Active | Used in galvanizing |
| Aluminum (Al) | -1.66 | Highly Active | Naturally forms a protective oxide layer |
| Carbon Steel | ~ -0.60 to -0.85 | Moderately Active | Prone to rust, needs protective coating |
| Lead (Pb) | -0.13 | Moderate | |
| Stainless Steel 304 (passivated) | +0.05 to -0.20 | Stable | Forms passive oxide layer |
| Stainless Steel 316 (passivated) | +0.03 to -0.13 | More Stable | Preferred for marine environments |
| Copper (Cu) | 0.34 | Very Stable | High galvanic risk with aluminum |
| Brass (Cu-Zn alloy) | 0.35 | Very Stable | Same as above |
| Bronze (Cu-Sn alloy) | +0.30 to +0.40 | Very Stable | |
| Silver (Ag) | 0.8 | Extremely Stable | Rarely used in structural fasteners |
| Titanium (Ti) | +0.10 to +0.30 | Extremely Stable | Excellent compatibility with aluminum |
| Platinum (Pt) | 1.2 | Noble / Non-Corroding | Not used in general fastening |
Galvanic Corrosion Principle:
- The metal with the more negative potential acts as the anode and will corrode preferentially when in contact with a more noble (less reactive) metal.
- The larger the potential difference, the higher the risk of galvanic corrosion in the presence of an electrolyte (moisture, salt, etc.).
- A difference of > 0.25–0.5V is considered risky and requires mitigation (insulation, protective coatings, or selecting compatible materials).
Compatibility with Aluminum (Risk by Potential Difference):
| Risk Level | Metal | Recommendation |
| ✅ Safe (<0.25V) | Aluminum, Titanium | Can be used in direct contact safely |
| ⚠️ Moderate (0.25–0.5V) | Zinc-plated steel, Stainless 316 | Use insulating washers or anti-corrosion paste |
| ❌ High (>0.5V) | Copper, Brass, Silver | Do NOT use in direct contact with aluminum |
FAQs About Galvanic Series
This is due to galvanic corrosion — an electrochemical reaction when two dissimilar metals are in contact in the presence of an electrolyte (like water). Aluminum, being more anodic, corrodes faster when coupled with more noble metals like stainless steel or copper.
- Best Options: Stainless steel 316 or titanium
- Protection Tips: Add insulating sleeves/washers and apply anti-corrosion coatings.
Avoid fasteners made of:
Brass
Copper
Carbon steel (uncoated)
These metals have high galvanic potential differences with aluminum and will accelerate corrosion.
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