1. Duct tape and ingenuity at a distance, again

Andy Weir’s The Martian returns because a corroded joint in orbit cannot be wrapped in duct tape either. The fix must be designed in before launch. Galvanic mitigation is not exciting work, but it is the kind of work that prevents quiet failures years into a mission.

This entry reads about galvanic mitigation strategies and material pairings.

2. The first defense: compatible pairs

The simplest mitigation is to use metals that are close to each other in the galvanic series. Common compatible groupings for spacecraft include:

  • Aluminum with aluminum, or with cadmium-plated steel fasteners.
  • Titanium with titanium, stainless steel, or nickel alloys.
  • Gold-plated contacts with gold or nickel underplates.

The most risky pairings are large-area noble metals coupled to small-area active metals. Aluminum fasteners into a copper bus bar, for example, are a classic failure waiting to happen.

3. The second defense: electrical isolation

When dissimilar metals must meet, they can be isolated:

  • Dielectric washers and sleeves: nylon, G-10, or other insulators break the electrical path through fasteners.
  • Insulating films and tapes: anodized layers, conversion coatings, or polymer films separate surfaces.
  • Gaskets and shims: non-conductive gaskets between flanges prevent metal-to-metal contact over a large area.

A guide to nylon washers for galvanic isolation notes that even a thin washer can stop the electrochemical circuit if it is designed to cover the full contact area and survive the mechanical load.

4. The third defense: coatings and surface treatments

Coatings can make an active metal behave more nobly, or can simply block the electrolyte:

  • Anodizing: thick aluminum oxide on aluminum parts increases corrosion resistance and electrical resistance.
  • Conversion coatings: chromate or non-chromate conversion coatings on aluminum provide a barrier.
  • Plating: cadmium or zinc plating on steel fasteners reduces the potential difference with aluminum.
  • Passivation: stainless steel passivation restores the protective oxide layer.

The key is that the coating must remain intact. A scratch that exposes the base metal can create a small anode and a large cathode, accelerating local corrosion.

5. The fourth defense: design for drainage and cleanliness

Moisture and contamination are the electrolyte. Design can limit them:

  • Avoid crevices where water can collect.
  • Provide drainage paths so condensation does not sit at joints.
  • Keep assemblies clean and dry before launch.
  • Use controlled storage humidity before flight.

6. Carbon composite special case

MSFC-HDBK-3697 notes that contacts between graphite-based composites and metals should be treated as dissimilar metal couples and sealed per NASA-STD-6012. Carbon fiber is conductive and noble, so it can aggressively corrode aluminum if the two touch directly.

7. What this changes

  • Galvanic mitigation is layered: material selection, isolation, coatings, and design.
  • Fasteners and joints are the most common failure locations.
  • The next entry will translate these findings into requirements for the desktop.