Selective-Phase Corrosion
Definition
Attack that preferentially dissolves one phase or element from a multi-phase alloy, leaving the other phase intact but structurally weakened. Dezincification of brass is the textbook example.
- Mechanism
- Preferential dissolution of one phase or element from an alloy
- Example
- Dezincification of brass
- Result
- Remaining phase intact but structurally weakened
Common questions
Why is selective-phase corrosion dangerous even though the object may look intact?+
The outer shape and dimensions can remain largely unchanged because the remaining phase keeps its form, while the loss of the dissolved element leaves a porous, brittle structure that can fail well below its expected strength.
How is dezincification typically distinguished from other forms of corrosion during examination?+
It shows a characteristic colour change, from the yellow of brass toward a copper-red tone, alongside a porous or spongy texture where the zinc has been leached out, which is not seen in general surface corrosion.
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...
- Galvanic Corrosion
- Electrochemical attack that accelerates the dissolution of the more active (anodic) metal when two dissimilar metals are electrically coupled in an electrolyte.
- 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...
- 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...