"304ss v aluminium corrosion"

Question:

"I am assessing the durability of nickel coated brass fasteners against 304 stainless fasteners when used on aluminium boat hulls. The 304 stainless fasteners appear to speed up the corrosion of the aluminium where they come into contact with each other. Is this expected? If so why? Any info would be greatly appreciated."

Answer:

You are experiencing what is common known as galvanic corrosion. Aluminum is anodic to 304SS; therefore, when they are electrically connected the 304SS will act as a cathode in the corrosion reaction, accelerating corrosion of the aluminum. The corrosion rate will depend on the area ratios between the 304SS and aluminum. Large cathode-to-anode area ratios are particularly detrimental.

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