BeginnerTopic 30 of 100Materials & Chemical
Galvanic and pitting corrosion
Dissimilar metals or localised attack cause rapid damage.
In depth
Galvanic corrosion occurs when dissimilar metals contact in an electrolyte (anode corrodes); keep anode/cathode area ratio large. Pitting is localised attack in passive metals by chlorides; crevice, intergranular, stress corrosion cracking, erosion-corrosion, and dealloying are other forms.
Key points
- Area effect
- Pitting resistance equivalent
- SCC needs stress + environment
ExampleAluminium rivets in a copper sheet corrode quickly in seawater.
What is Galvanic and pitting corrosion?
Dissimilar metals or localised attack cause rapid damage.
Why is it important to understand galvanic and pitting corrosion?
Galvanic and pitting corrosion are common causes of rapid failure, and they are often avoidable with the right material and design.
What is galvanic corrosion?
Accelerated corrosion of the less noble metal when it is electrically connected to a more noble metal in an electrolyte.
Why is pitting dangerous?
It produces deep, localised holes that can perforate thin walls quickly even when the overall loss of material is small.
How is Galvanic and pitting corrosion used in practice?
Typical applications include avoiding an aluminium fastener in direct contact with stainless steel on a boat, inspecting a stainless tank for pitting near welds and designing drainage to stop water sitting in crevices on a structure.
What should I learn before Galvanic and pitting corrosion?
Study "Corrosion basics" first (topic 29 of 100 in Materials & Chemical). It covers the groundwork this topic builds on.
What are the key points of Galvanic and pitting corrosion?
Area effect. Pitting resistance equivalent. SCC needs stress + environment.
Can you give an example of Galvanic and pitting corrosion?
Aluminium rivets in a copper sheet corrode quickly in seawater.
What comes after Galvanic and pitting corrosion?
The next topic is "Corrosion prevention", which builds directly on this one.
How difficult is Galvanic and pitting corrosion?
It is classed as Beginner in Materials & Chemical (topic 30 of 100). It is an entry-level topic. It relies only on basic school mathematics and the ideas introduced earlier in this discipline.