Galvanic Corrosion

What is Galvanic Corrosion?

Galvanic corrosion (also known as bimetallic or dissimilar‑metal corrosion) is an electrochemical process where two dissimilar stainless steel grades, when in electrical contact and exposed to an electrolyte, form a galvanic couple: the anode corrodes faster, while the cathode corrodes more slowly.

How Galvanic Corrosion Occurs in Materials

When materials of differing electrode potentials are coupled in an electrolyte, the less noble (more active) material becomes anodic. It corrodes preferentially, while the more noble material acts as a cathode. Factors such as relative electrode potential differences, surface‑area ratio, electrical contact, and electrolyte chemistry (e.g. saltwater) determine the rate and severity.

How to Avoid Galvanic Corrosion in Stainless Steel Applications

To avoid galvanic corrosion in stainless steel:

• Use metals with similar electrode potentials to minimise nobility gaps. 
• Provide electrical insulation or buffers (e.g. nylon washers, clamp liners, insulating coatings) between stainless steel and other metals. 
• Apply coatings or plating (e.g. galvanising carbon steel fasteners with zinc) to prevent stainless steel from acting as a cathode that accelerates corrosion.