Galvanic Corrosion
Definition
Electrochemical attack that accelerates the dissolution of the more active (anodic) metal when two dissimilar metals are electrically coupled in an electrolyte.
- Requirement
- Two dissimilar metals electrically coupled in an electrolyte
- Effect
- Accelerated dissolution of the anodic (more active) metal
- Analysis use
- Fastener and dissimilar-metal fitting failure analysis
Common questions
How does galvanic corrosion inform failure analysis of a fastener or fitting?+
An examiner checks whether two different metals were in contact, such as a steel bolt in an aluminium fitting with moisture present, since accelerated pitting or material loss concentrated at that contact point points to galvanic action rather than uniform environmental corrosion.
What distinguishes galvanic corrosion from ordinary uniform rusting?+
Uniform corrosion attacks a single metal fairly evenly across its exposed surface from environmental exposure, while galvanic corrosion is localized and asymmetric, concentrating damage on the more active metal specifically at or near its contact with the more noble metal.
Related terms
- Corrosion Fatigue
- Fatigue crack initiation and growth accelerated by a corrosive environment. Unlike SCC, it does not require a specific environment-material combination and can...
- Crevice Corrosion
- Corrosion in confined geometry , under gaskets, at lap joints, between fastener and plate , driven by oxygen depletion and acidification inside...
- Pitting Corrosion
- Localised attack producing narrow, deep craters where the passive film breaks down. Pitting is self-propagating once initiated because the pit interior becomes...
- Selective-Phase Corrosion
- Attack that preferentially dissolves one phase or element from a multi-phase alloy, leaving the other phase intact but structurally weakened. Dezincification of...
- Stress-Corrosion Cracking (SCC)
- A failure mode combining sustained tensile stress with a specific corrosive environment, producing branching, often intergranular cracks that grow at stress intensities...