Ever wondered why that aluminum boat cleat with stainless steel screws corroded so quickly? Or why your copper plumbing disintegrated where it connected to steel pipes? The culprit is galvanic corrosion – nature’s own battery effect that can destroy metal components with surprising speed.
When two different metals touch in a damp environment, whether it’s sea spray, humidity, or full immersion, they create a natural electrical circuit. One metal becomes the sacrificial anode, essentially dissolving itself to protect its neighbor. This isn’t random chance – it follows the predictable hierarchy known as the galvanic series.
Metals Listed by Anodic Index
The anodic index (or galvanic potential) measures a metal’s tendency to corrode in the presence of another metal when coupled in an electrolyte. Metals with more negative values are more anodic (more likely to corrode) and serve as sacrificial anodes when connected to metals with more positive values.
| Metal/Alloy | Anodic Index (V) |
|---|---|
| Magnesium | -1.75 |
| Magnesium alloys | -1.60 to -1.63 |
| Zinc | -1.10 |
| Aluminum 1100 | -0.96 |
| Cadmium | -0.80 |
| Aluminum 2024 | -0.75 |
| Mild steel | -0.70 |
| Cast iron | -0.69 |
| SS 410 (Active) | -0.65 |
| Low alloy steel | -0.60 |
| SS 304 (Active) | -0.58 |
| SS 316 (Active) | -0.57 |
| Austenitic stainless steel (active) | -0.56 |
| Lead | -0.55 |
| SS 430 | -0.50 |
| Tin | -0.49 |
| Nickel (active) | -0.40 |
| Brass | -0.40 |
| Copper | -0.35 |
| Bronze | -0.33 |
| Inconel (Passive) | -0.22 |
| Nickel (passive) | -0.20 |
| Monel | -0.15 |
| Titanium | -0.15 |
| Silver | -0.15 |
| SS 304 (Passive) | -0.08 |
| SS 316L (Passive) | -0.05 |
| Austenitic stainless steel (passive) | -0.05 |
| Gold | +0.00 |
| Platinum | +0.15 |
| Graphite | +0.25 |
Notes About Table:
- Values are approximate and may vary depending on environmental conditions (seawater, freshwater, soil, atmosphere).
- A difference of 0.25V or greater between two metals significantly increases galvanic corrosion risk when connected.
- Surface area ratio matters - a small anode connected to a large cathode creates the most severe corrosion conditions.
- Galvanic corrosion requires an electrolyte (moisture) to occur - dry environments greatly reduce the risk.
Galvanic Reaction Chart
Notes About Chart:
- Metals higher on the chart (more negative potential) will corrode preferentially when connected to metals lower on the chart.
Conclusion:
If you have questions about the galvanic compatability needs within your projects or equipment, please feel free to contact our engineers, and product experts. Also, be sure to check out our catalog here at MISUMI USA, where we carry large array of metallic pipe fittings, and fastener offerings, including threaded pipe fittings & flanges.
Author: Scott Bredemann | Updated: 4/8/2025
Disclaimer:
The content on this webpage is for informational purposes only. MISUMI makes no guarantees, expressed or implied, regarding the accuracy, completeness, or validity of the information. Performance parameters, tolerances, designs, materials, or processes should not be assumed to reflect third-party suppliers’ or manufacturers’ deliverables within MISUMI’s network. Buyers are responsible for specifying their part requirements