Galvanic Corrosion in Sheet Metal Assemblies: How to Avoid It
Engineering Team | Anjue Metal | Updated Nov 5, 2026 | 8 min read
Put aluminum and steel in the same enclosure with moisture and you get a battery - and the aluminum loses. Galvanic corrosion is one of the most expensive mistakes in sheet metal enclosures because it is designed in quietly and shows up a season later in the field. Here is what it is, which pairs are risky, and how to design it out.
1. What galvanic corrosion actually is
When two different metals touch in the presence of an electrolyte (rain, condensation, salt spray), the more "active" metal corrodes to protect the "noble" one. It is a small battery you did not ask for. The driving force is the difference in electrode potential between the two materials.
2. The galvanic series and the classic aluminum + steel risk
In the galvanic series, aluminum sits near the active end and steel (and especially stainless steel and copper) sit toward the noble end. An aluminum enclosure fastened with plain steel screws, or an aluminum panel bolted to a steel frame, will corrode the aluminum at the joint - often within a single wet season outdoors.
High-risk pairs: aluminum + carbon steel, aluminum + copper, and magnesium with almost anything. Lower-risk: aluminum 5052 with 6061 (both aluminum), or 304 with 316L stainless (same family).
3. Where it shows up in enclosures
Outdoor telecom and solar enclosures are the usual victims: an aluminum body with steel hinges or mounting brackets, stainless inserts pressed into aluminum, or a steel cable gland landing on an aluminum panel. Marine and road-salt environments make it worse by orders of magnitude.
4. Design fixes that stop it
Isolate the metals. Use non-conductive washers, sleeves or paint breaks so the two metals never share an electrolyte path. A thin nylon washer between an aluminum panel and a steel bracket is often enough.
Choose compatible fasteners. For aluminum structures use aluminum or stainless fasteners sized and coated for the job; avoid bare carbon steel. Where stainless meets aluminum, insulate the interface.
Use coatings as a barrier. A continuous powder coat or anodize layer breaks the electrolyte path - but a scratched coating at a fastener hole can become the exact spot corrosion starts, so combine coating with isolation, don't rely on paint alone.
Design for drainage and drying. Don't let water pool at joints. Sloped surfaces, drain holes and avoiding crevices that trap moisture remove the electrolyte the reaction needs.
5. When it is acceptable
Indoor, climate-controlled equipment with no condensation risk can often mix metals safely. The question to ask on every RFQ is simply: "Will this joint ever see moisture?" If yes, isolate or match the materials.
Frequently Asked Questions
Frequently Asked QuestionsAluminum combined with carbon steel or copper is the classic high-risk pair - the aluminum corrodes rapidly at the joint when moisture is present. Aluminum with another aluminum alloy, or 304 with 316L stainless, is far safer.
It helps by breaking the electrolyte path, but a scratch at a fastener hole can become the exact starting point of corrosion. Combine coating with physical isolation (non-conductive washers/sleeves) rather than relying on paint alone.
Only if the interface is isolated. Pressing a bare stainless insert into aluminum creates a noble-active couple at the joint; use insulated or coated inserts, or accept the risk only in dry, indoor environments.
State the service environment (indoor dry, outdoor, marine, road salt) and ask the supplier to call out mixed-metal joints and how they will be isolated. The single question 'will this joint see moisture?' decides most of the risk.
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