6.4 Corrosion Flashcards

1
Q

What is the difference between corrosion and erosion

A

Erosion occurs due to mechanical actions

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2
Q

Why do metals such as gold and silver not corrode

A

As they are noble metals and are chemically pure

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3
Q

What is galvanic corrosion

A

The corrosion of two different dissimilar metals in the presence of an electrolyte

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4
Q

What is microbiological corrosion

A

From bacteria fungi or moulds

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5
Q

How can corrosion of magnesium be identified

A

A grey powder

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6
Q

What is filiform corrosion

A

Produces a worm like track of corrosion

Usually when relative humidity is 78-90%

Can lead to inter granular if not removed

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7
Q

What is pitting corrosion

A

First appears as a white powdery deposit. It starts on the surface and extends vertically in to the material

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8
Q

What is the most common type of corrosion on aluminium and magnesium

A

Pitting

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9
Q

What is inter granular corrosion

A

Attacks the grain boundaries with sometimes no indication on the surface

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10
Q

What is exfoliation corrosion

A

An advanced form of inter granular corrosion.

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11
Q

Where is exfoliation corrosion most common

A

Wrought products

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12
Q

What is fretting corrosion

A

Damage that can be caused in between two highly loaded surfaces which are not meant to move against each other

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13
Q

What is crevice corrosion

A

A type of concentration cell corrosion. This is corrosion of metal in a metal to metal joint, and corrosion at the edge of a joint. Seals of joints and gaps and use of protective coatings in the fraying surface area can reduce crevice corrosion

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