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Corrosion > Corrosion of metals and alloys > Flashcards

Corrosion of metals and alloys Flashcards

1
Q

A specialized type of attack that takes place at the grain boundaries of a metal.

A

Intergranular corrosion / intergranular attack

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2
Q

A type of corrosion where the corroded areas occur in a manner evenly distributed across the material being attacked.

A

uniform corrosion / general corrosion

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3
Q

Type of corrosion when two different metallic materials are electrically connected and placed in a conductive solution (electrolyte), an electric potential exists.

A

Galvanic corrosion / dissimilar metal corrosion / bimetallic corrosion

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4
Q

Is a localized type of corrosion occurring within or adjacent to narrow gaps.

A

Crevice corrosion

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5
Q

Is characterized by a highly localized loss of metal. The initiation of a pit is associated with the breakdown of the protective film on the metal surface.

A

Pitting corrosion

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6
Q

Is usually caused by an aqueous or gaseous corrodent flowing over the metal surface or impinging upon it.

A

Erosion corrosion

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7
Q

Is a phenomenon where cracks form and propagate in a material due to the combined effects of sustained tensile stress and exposure to a corrosive environment.

A

Stress corrosion cracking

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8
Q

Refers to the degradation of metals caused by the activity of living organisms.

A

Biologically influenced corrosion / microbial-induced corrosion

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9
Q

This type of corrosion targets alloys, which are mixtures of different metals.

A

Selective Leaching

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10
Q

is the term to describe the leaching of zinc
from brass.

A

Dezincification

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11
Q

is the term used to describe the selective leaching of iron from gray cast iron.

A

Graphite corrosion

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12
Q

Degradation that occurs when hydrogen penetrates the surface of a metal

A

Hydrogen Damage

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13
Q

The most drastic form of liquid metal attack is the instantaneous fracture of the solid metal in the presence of stress

A

liquid metal embrittlement

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14
Q

Requires elongated (parallel-shaped) grains, a susceptible grain boundary condition, and a relatively severe environment

A

Exfoliation

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15
Q

Is the cracking of a metal or alloy under the combined action of a corrosive environment and repeated or fluctuating stress.

A

Corrosion fatigue

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16
Q

Is when metals and alloys fail by cracking when subjected to cyclic or repetitive stress.

A

Fatigue failure

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17
Q

Metals with semipermeable coatings or films may undergo a type of corrosion resulting in numerous meandering threadlike filaments of corrosion beneath the coatings or films.

A

Filiform corrosion

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18
Q

____ cells may be formed when two dissimilar metals are in contact or due to the heterogeneity of the same metal surface.

A

Dissimilar electrode

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19
Q

____ are formed when the electrodes are identical but are in contact with solutions of differing composition.

A

Concentration cells

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20
Q

Formed when electrodes of the same metal, each of which is at a different temperature, are immersed in an electrolyte of the same initial composition.

A

Differential temperature cell

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21
Q

This situation arises in cell when a significant difference in metal ion concentration exists over a metal surface.

A

Metal ion concentration cell

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22
Q

____ can develop at any point where the oxygen in the air is not allowed to diffuse into the solution, thereby creating a difference in oxygen concentration between two points.

A

Oxygen concentration cell

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23
Q

It is a graphical representation of metal stability and corrosion products.

A

Potential-Ph Diagrams / Pourbaix Diagram

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24
Q

Under this condition of potential and pH, the metal remains in metallic form and is free from corrosion

A

Immunity Zone

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25
Q

Under these condition of potential and pH, the metal corrodes

A

Corrosion Zone

26
Q

Under this condition of potential and pH, protective layer of the metal’s hydroxide or oxide form on iron and further corrosion of metal doesn’t take place.

A

Passive zone

27
Q

The potential change caused by net current to or from an electrode, measured in volts.

A

Polarization

28
Q

_____ is a manifestation of the relative changes in the activation energies for dissolution and deposition, when equilibrium is disturbed.

A

Activation polarization

29
Q

Polarization of an electrolytic cell resulting from changes in the electrolyte concentration due to the passage of current through the electrode/solution interface.

A

Concentration Polarization

30
Q

The change in voltage associated with
effects of the environment and the circuit between the anode and cathode sites.

A

Resistance Polarization / Ohmic Polarization / IR Drop

31
Q

(T/F) Reaction rates increases with temperature

A

True

32
Q

(T/F) Increasing the velocity of the corrodent will increase the corrosion rate

A

True

33
Q

(T/F) When using immune materials, increasing the velocity could lower corrosion rate

A

False - it should be passive materials

34
Q

(T/F) Rough surface or crevice can facilitate formation of concentration cell

A

True

35
Q

____ is a complicated electrochemical process taking place in corrosion cells consisting of base metal, metallic corrosion products, surface electrolytes, and the atmosphere.

A

Atmospheric corrosion

36
Q

Refers to the length of time during which the metal surface is covered by a film of water.

A

Time of wetness

37
Q

Occurs when the temperature of the metal surface is below the dew point of the atmosphere

A

Dew

38
Q

Creates even thicker layers of electrolyte on
the surface than dew

A

Rain

39
Q

High acidity and high concentrations of sulfates and nitrate can be found in ___ droplets in areas of high air pollution

A

Fog

40
Q

Can promote corrosion because of their hygroscopic nature.

A

Dust

41
Q

Period when the metal is covered with a spontaneously formed oxide and aqueous layer

A

Induction period

42
Q

Period when the oxide layer transforms into a fully developed layer of corrosion products.

A

Transition period

43
Q

Period when the surface being fully covered by corrosion product and reach constant corrosion rate

A

Stationary period

44
Q

Defined as the ratio of deposition rate of any gaseous compound and the concentration of that compound in the atmosphere.

A

dry deposition velocity

45
Q

Is a generic term that applies to high carbon-iron alloys containing silicon.

A

Cast Iron

46
Q

Alloy that contains 2% to 4% carbon and 1% to 3% silicon.

A

Gray Cast Iron

47
Q

Alloys that have practically all of the carbon in the form of iron carbide. Silicon content is low because this element promotes graphitization.

A

White cast iron

48
Q

Alloy that are produced by high-temperature heat treatment of white iron of proper composition

A

Malleable Cast Iron

49
Q

An alloy where the graphite is present as nodules or spheroids as a result of a special treatment of the molten metal.

A

Ductile Cast Iron

50
Q

Alloy where the silicon content of gray cast iron is increase to 14%, it becomes extremely corrosion resistant to
many environment

A

High Silicon Cast Iron

51
Q

Alloy that is composed of up to 2.14%
carbon

A

Steels

52
Q

Alloy containing at least 11%
chromium.

A

Stainless Steels

53
Q

Alloy that can be hardened by heat treatment similar to ordinary steel.

A

Martensitic
Stainless Steels

54
Q

An alloy that is essentially nonmagnetic and cannot be hardened by heat treatment.

A

Austenitic Stainless Steels

55
Q

An alloy that cannot be hardened by heat treatment. Can only be hardened by cold working.

A

Ferritic Stainless Steels

56
Q

Alloy that is hardened and strengthened by solution-quenching, followed by heating for substantial times at temperature approximately in the range of 800 to 1000 F.

A

Precipitation-hardened Stainless Steels

57
Q

It is different from most other metals in that it combines corrosion resistance with high electrical and head conductivity, formability, machinability, and strength when alloyed

A

Copper

58
Q

Lightweight metal having good corrosion resistance to the atmosphere and most aqueous media

A

Aluminum

59
Q

Has the lowest density of all structural metals (1.7g/cm3 vs steel with 7.85g/cm3)

A

Magnesium

60
Q

It is ductile and tough metal mainly because of its face-centered cubic structure.

A

Nickel

61
Q

Consists of 10-30% copper
and 70-90% nickel.

A

Cupronickels

Corrosion (6 decks)

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