Galvanic Corrosion Chart and Calculator

If you put two dissimilar metals together in a moist or corrosive environment and don't check if they're compatible, you're asking for trouble—these setups often fail much sooner than expected. The Galvanic Corrosion Compatibility Calculator on this page helps you measure the risk by showing voltage difference and the level of corrosion threat, using each metal’s electrode potential and the environment. This is relevant anywhere you can get two metals and some moisture—marine work, industrial setups, or anywhere exposed to weather or humidity. What follows covers the main formulas used, an example calculation, a hands-on technical breakdown, and an FAQ.

What is galvanic corrosion?

When two different metals touch in the presence of moisture or any electrolyte, they can set up a weak electrical circuit. The less “noble” metal corrodes faster, while the more “noble” one resists. The further apart the metals are in the electrochemical series, the stronger the reaction and the faster the corrosion.

Simple Explanation

Think about how a battery works: two different metals in a liquid let a current flow. In structural or mechanical connections, the less noble metal acts as the anode and will lose material; the other metal is the cathode and doesn’t corrode. If you keep your metals with similar electrode potentials, you keep this voltage (and the corrosion rate) small.

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Galvanic Corrosion Process Diagram

How to Use This Calculator

1. Select the first metal from the Metal 1 dropdown.
2. Select the second metal from the Metal 2 dropdown.
3. Choose the operating environment from the Environment dropdown.
4. Click Calculate to see your result.

Galvanic Corrosion Compatibility Calculator

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Mathematical Formulas

The calculations here use each metal’s position in the electrochemical series to get a voltage difference. This gives you a starting point for corrosion risk, but real environments always shift things a bit—so a factor for the operating environment is applied on top.

The galvanic corrosion compatibility calculator uses the electrochemical series to determine corrosion potential:

Where:

• E_cathode = Standard electrode potential of the more noble metal (V)
• E_anode = Standard electrode potential of the less noble metal (V)
• Environment Factor = Multiplier based on corrosive environment (0.2-1.0)

Simple Example

Aluminum (E = -0.76 V) bolted to a copper busbar (E = +0.34 V) in seawater (factor = 1.0):

• ΔV = |0.34 − (−0.76)| = 1.10 V
• V_adjusted = 1.10 × 1.0 = 1.10 V
• Risk level: Very High — the aluminum corrodes. Use isolation or sacrificial anodes.

Understanding Galvanic Corrosion in Engineering Applications

Galvanic corrosion is a routine headache for anyone building systems that use more than one kind of metal. If you put two different metals in electrical contact and there's any sort of conductive liquid or moisture, one metal will corrode faster—usually the less noble one—while the other one is spared.

The Electrochemical Process

This all comes down to electrode potential differences. When two metals with different potentials are connected and exposed to an electrolyte, electrons go from the lower-potential (more negative) metal to the higher one. The current leaves the anodic metal (which then dissolves a bit) and travels to the cathodic metal (which doesn’t dissolve).

This setup needs four things:

• Anode (corroding metal): This is where material loss takes place, as atoms lose electrons to the circuit and enter the electrolyte.
• Cathode (protected metal): This metal accepts electrons; it won’t be eaten away by this process.
• Electrolyte: You need water or some other conductive path between the metals—no moisture, no galvanic cell.
• Metallic path: The two metals have to be electrically connected, either directly or through a conductor.

The Electrochemical Series

The calculator uses standard electrode potentials from the electrochemical series—a practical, if idealized, way to rank metals by how likely they are to give up electrons. The more negative the potential, the quicker the metal corrodes when paired with a more positive one. These values are reference points. In practice, actual corrosion rates will depend on alloying, coatings, and environment.

A snapshot of common values (approximate):

• Magnesium: -1.66 V
• Zinc: -1.18 V
• Aluminum: -0.76 V
• Steel: -0.25 V
• Copper: +0.34 V
• Silver: +0.52 V
• Gold: +0.80 V

Environmental Factors

Your installation environment matters—a lot. The more ions, water, and contaminants you’ve got, the higher the risk. In practice, results from theoretical voltage calculations are tweaked using an environment factor:

Seawater (Factor: 1.0): Corrosion doesn’t get much faster than this. High conductivity, aggressive to most metals. Components here usually need extra precautions like isolation or sacrificial anodes.

Industrial Atmosphere (Factor: 0.8): Pollutants or acid vapors with moisture make for more aggressive corrosion than most inland sites. Corrosion is often visible after a season or two.

Urban Atmosphere (Factor: 0.6): Still risky, with the mix of everyday pollutants and moderate humidity present in a city.

Rural Atmosphere (Factor: 0.4): Less activity here, but moisture and oxygen are enough long-term to create issues for bad metal pairs.

Indoor/Dry (Factor: 0.2): As close as you’ll get to “safe” in everyday environments, though not completely immune in the long term.

Practical Applications in Automation

In automation and machinery work, you run into this problem when multiple metals are used together in places that might get wet, salty, or humid. For example, linear actuators with aluminum housings and steel or zinc hardware, or any setup that combines wiring (copper) with mounting brackets (aluminum or steel) may see problems if not addressed at the design stage.

Some combinations to watch out for:

• Aluminum parts with steel fasteners outdoors or near the ocean
• Copper wires bolted or soldered to aluminum frames or covers
• Stainless and mild steel joined directly together
• Zinc-plated bolts with copper busbars

Worked Example

Take an automation enclosure made from aluminum (E = -0.76 V) fitted with copper terminals (E = +0.34 V) in an industrial atmosphere:

Step 1: Find the potential difference
ΔV = |0.34 - (-0.76)| = 1.10 V

Step 2: Adjust for the environment
V_adjusted = 1.10 × 0.8 = 0.88 V

Step 3: Rate the risk
At 0.88 V, this is a very high-risk combination for corrosion. Expect the aluminum to deteriorate faster than usual. Without intervention, reliability drops significantly.

What helps:

• Insulators separating the metals (use nylon or polymer washers or insert plates)
• Paint or anodize the aluminum to create a barrier
• Swap to stainless if a matching material is an option
• Add a sacrificial anode if replacing or isolating isn’t possible

Prevention Strategies

Material Selection: Whenever possible, keep metals close together in the electrochemical series—anything with less than 0.25 V between them is low risk for most situations.

Electrical Isolation: A non-metallic washer, gasket, or sleeve is sometimes all you need to break the circuit and halt corrosion.

Protective Coatings: Paint, powder coat, or plate the more active metal, but remember, once the coating is scratched or wears through, you lose most of this protection.

Cathodic Protection: In tougher environments, fit a replaceable anode (for example, a bit of zinc) to give up material so more critical parts don’t have to.

Environmental Control: If you can keep joints dry and clean, the galvanic risk drops accordingly. Proper sealing makes a difference.

Design Considerations for Linear Actuators

Choosing and combining materials for actuators isn't just a matter of cost or strength—corrosion impacts long-term function. Here’s what matters:

Housing Materials: Aluminum is light and strong, but when combined with steel or copper, expect trouble unless it’s anodized or otherwise protected.

Fastener Selection: Stainless may cost more upfront but is usually worth it for long-term durability, especially compared to zinc-plated hardware in a wet or exposed system.

Electrical Connections: Using tin-plated copper reduces both connection resistance and galvanic problems.

Sealing and Gaskets: Keep out the moisture and you prevent the problem before it starts.

Industry Standards and Testing

If you’re working in regulated fields, there are standards for how to check and manage galvanic corrosion:

• ASTM G71: Guide for Galvanic Corrosion Tests
• ISO 17475: Electrochemical test methods
• MIL-STD-889: Dissimilar metals

These outline test setups and what’s acceptable for given material pairs under various conditions.

Frequently Asked Questions

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