What stainless steel fasteners prevent galvanic corrosion?

Galvanic corrosion occurs when two dissimilar metals are electrically connected in a corrosive electrolyte, causing the more anodic metal to corrode faster. Stainless steel fasteners can both cause and prevent this issue depending on their grade and application. To prevent galvanic corrosion with stainless steel fasteners, consider these key strategies:

1. Material Compatibility: Select stainless steel grades that are close to the base metal on the galvanic series. Austenitic grades like 304 and 316 are often more cathodic (noble) than many common construction metals.

2. Use Similar Metals: Whenever possible, match stainless steel fasteners with stainless steel components or other metals with similar electrochemical properties.

3. Isolation Techniques: Employ insulating materials between dissimilar metals:

- Plastic or nylon washers

- Non-conductive gaskets

- Specialized coatings or paints

- Rubber or polymer sleeves

4. Protective Coatings: Apply appropriate coatings to both the fastener and base metal to create a barrier against electrolyte contact.

5. Environmental Control: Reduce exposure to electrolytes by:

- Using seals and enclosures

- Implementing proper drainage

- Controlling humidity and temperature

6. Cathodic Protection: In severe environments, consider sacrificial anodes or impressed current systems.

Type 316 stainless steel is particularly effective in corrosive environments due to its molybdenum content, which enhances resistance to chlorides and other corrosive agents. For aluminum structures, 5000-series fasteners are often preferable, while specially coated steel fasteners may be better for copper assemblies.

Regular inspection and maintenance remain crucial for long-term corrosion prevention, especially in marine, industrial, or high-humidity applications where galvanic corrosion risks are highest.