アルミニウムとステンレスのガルバニック腐食を防ぐには？

When aluminum and stainless steel touch, corrosion can start silently. Left unchecked, it damages parts, weakens joints, and increases maintenance costs.

You can prevent galvanic corrosion between aluminum and stainless steel by isolating the metals with non-conductive materials, coatings, or proper design.

Mixing metals without planning leads to expensive repairs. But with the right steps, you can use both materials together safely. Let’s explore how.

What materials can isolate aluminum from stainless steel?

Many engineers overlook this step. But proper isolation is the most effective way to stop galvanic corrosion between aluminum and stainless steel.

You can isolate aluminum from stainless steel using plastic washers, rubber gaskets, nylon bushings, or painted surfaces that break the electrical path.

Galvanic corrosion happens when two different metals touch in the presence of an electrolyte like water. One metal becomes the anode (corrodes), the other the cathode. Aluminum is the anode in this pair, meaning it will degrade faster.

Common Isolation Materials

These materials block the electrical current. No current = no galvanic reaction. Always ensure complete separation, not just surface-level protection.

Do dielectric coatings prevent galvanic corrosion?

A quick coating seems simple, but does it really stop corrosion between dissimilar metals?

Yes, dielectric coatings prevent galvanic corrosion by creating an insulating layer that blocks electrical flow between aluminum and stainless steel.

Dielectric coatings are non-conductive paints or films. They act like barriers between two different metals. These coatings stop the flow of electrons, which stops the corrosion reaction.

Common types include epoxy, polyurethane, and powder coatings. These are especially useful in marine or outdoor environments where moisture is always present.

Coating Types That Help Prevent Galvanic Corrosion

However, coatings must be continuous. If the coating is scratched or wears off, corrosion can start underneath. Always inspect coated parts regularly.

How to select fasteners to avoid corrosion?

Fasteners often get ignored, yet they are the most common failure points in mixed-metal designs.

To avoid corrosion, choose fasteners made of compatible metals or isolate them with washers, sleeves, or special coatings.

Using stainless steel bolts on aluminum sounds strong—but it creates a galvanic couple. Over time, the aluminum corrodes around the fastener. That weakens the joint and makes removal hard.

Recommended Fastener Choices for Aluminum Structures

If you must use stainless steel bolts, combine them with plastic or nylon washers and sleeves. These prevent direct contact. Also consider applying anti-corrosion paste or grease during assembly.

Is electrical insulation necessary to stop reactions?

It’s not just about the metals—it’s about how electrons move between them. Without a complete circuit, corrosion won’t start.

Yes, electrical insulation is necessary to stop galvanic corrosion because it breaks the circuit between dissimilar metals.

Galvanic corrosion acts like a tiny battery. The metal pair creates voltage. Moisture or another electrolyte connects them. Electrons flow, and aluminum dissolves.

You can block this by interrupting the path:

1. Use plastic gaskets or sleeves.
2. Apply full-surface coatings.
3. Avoid design traps that collect water.
4. Use isolating brackets or mountings.

Electrical Insulation Checklist

Even grounding the system doesn’t help if two dissimilar metals are directly touching. Insulation must be physical and total.

結論

Galvanic corrosion between aluminum and stainless steel is preventable. Isolate the metals, coat surfaces, choose the right fasteners, and stop current flow with proper insulation. With the right steps, you can combine these materials safely and effectively.