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API571 > Module 10 (uniformed or Localized Loss) > Flashcards

Module 10 (uniformed or Localized Loss) Flashcards

1
Q 
galvanic corrosion
critical factor (3)
A
  1. There must be two (or at least two) different metals
  2. The dissimilar metals must be electrically coupled together,.
  3. Both metals must be immersed or in contact with the same, continuous electrolyte
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2
Q

galvanic corrosion

The more noble material (_____) is protected by sacrificial corrosion of the more active material (___).

A

cathode / anode

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3
Q

galvanic corrosion

If there is a small anode-to-cathode exposed surface area ratio, the corrosion rate of the anode can be

A

very high.

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4
Q

galvanic corrosion
. If there is a large anode-to-cathode surface area ratio, the corrosion rate of the anode will be

The same metal may act as either an anode or a cathode in different situations

A

less affected.

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5
Q

galvanic corrosion

damage occurs where two different materials are joined at ____________(3)

A

welded, bolted, or rolled connections.

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6
Q

galvanic corrosion
_____ active material can suffer generalized loss in thickness or more aggressive localized loss adjacent to the point of connection, with the appearance of ___(3) ___

A

more /

crevice, grooving, or pitting corrosion

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7
Q

galvanic corrosion

a) The best method for prevention or mitigation is through

A

good design

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8
Q

galvanic corrosion

If only one can be coated, the more _______material should be the one coated

A

noble cathode

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9
Q

atmospheric corrosion

affected material

A

Carbon steel, low-alloy steels, and copper alloyed aluminum

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10
Q

atmospheric corrosion

Corrosion rates increase with temperature up to about ______ . Above _____, surfaces are usually too dry for corrosion to occur except under insulation.

A

250 °F / 250 °F

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11
Q

atmospheric corrosion

a. Marine environments can be very corrosive (about )
b. industrial environments that contain acids or sulfur compounds
c. Inland locations
d. Dry rural

A

a. 20 mpy
b. 5 mpy 10 mpy
c 1 to 3 mpy
d. <1mpy

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12
Q

atmospheric corrosion

appearance

A
  1. general or localized
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13
Q

atmospheric corrosion

prevention?

A

paint or coating

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14
Q

atmospheric corrosion

inspection (3)

A

VT / RT /UT

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15
Q

atmospheric corrosion

related mech?

A
  1. CUI

2. Concentration cell corrosion

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16
Q

CUI

affected materials?

A

Carbon steel, low-alloy steels, 300 series SS, 400 series SS, and duplex stainless steels.

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17
Q 
CUI
susceptible temp
CS
SS
Duplex
A

a. 10 °F (−12 °C) and 350 °F (175 °C) - CS
b. 140F-280F for SS
c. 280-350F for duplex

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18
Q

CUI

The extent of CUI attack depends on the total amount of time the equipment remains ____from exposure to _____.

A
  1. wet

2. wet insulation.

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19
Q

CUI
higher operating temperature will result in a _____ corrosion rate, the total amount of attack over a long period of time may occur at a _____temperature if the metal remains wet for significantly longer periods of time at the lower temperature.

A

higher /

lower

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20
Q

CUI

CUI corrosion rates are _____to predict

A

difficult

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21
Q

CUI

appearance (2)

A

a. corrosion can appear to be carbuncle type pitting

b. 300S are subject to SCC is chloride are present

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22
Q

prevention
1. mitigation is best achieved by _________
2. ______ aluminum coatings have been used on carbon steels.
3. Thin _____foil wrapped on stainless steel piping and equipment beneath the insulation can provide an effective barrier, partly due to the galvanic effect of the aluminum in preventing Cl− SCC in stainless
steel.
4. While ____cell foam glass materials will hold less water and, studies show that an ____cell structure provides a path for water vapor to escape faster, allowing the insulation to dry quicker. Faster drying time, corresponding to less metal wetting time, should help mitigate CUI. Types of open cell insulation that limit and delay water ingress have been developed.

A
  1. coating
  2. Flame-sprayed
  3. aluminum
  4. closed- / open
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23
Q

CUI

inspection (2)

A

infrared thermography / neutron backscatter

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24
Q

Cooling Water Corrosion

appearance (2)

A

General or localized corrosion

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25
Q

Cooling Water Corrosion

Higher cooling water temperature causes ____corrosion rates

A

increased

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26
Q

Cooling Water Corrosion
If the process-side temperature is above____ , a scaling potential exists with fresh water and becomes more likely as process temperatures increase and as cooling water inlet temperatures rise.

A

140 °F

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27
Q

Cooling Water Corrosion

Brackish and salt water outlet temperatures above about ____may cause serious scaling.

A

115 °F

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28
Q

Cooling Water Corrosion

Brackish and salt water outlet temperatures above about ____may cause serious scaling.

A

115 °F

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29
Q

Cooling Water Corrosion

Increasing _____content tends to increase carbon steel corrosion rates

A

oxygen

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30
Q

Cooling Water Corrosion

suggested velocity?

A

3fps

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31
Q

Cooling Water Corrosion

_____ alloys can suffer dezincification in fresh, brackish, and salt water systems.

A

Brass

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32
Q

Cooling Water Corrosion

temp____ for SS can suffer CLSCC

A

> 140F

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33
Q

Cooling Water Corrosion

temp____ for SS can suffer CLSCC

A

> 140F

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34
Q

Cooling Water Corrosion

_____carbon steel pipe or exchanger tubes may suffer severe weld and/or HAZ corrosion in fresh or brackish water.

A

ERW

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35
Q

Cooling Water Corrosion
prevention
a. Cooling water corrosion (and fouling) is best managed by proper ____3____ of cooling water systems
b. Process-side inlet temperatures of water-cooled exchangers should be maintained below____
c. With very few exceptions, cooling water should be on the ____side to minimize stagnant areas

A

a. design, operation, and chemical treatment
b. 140 °F (60 °C)..
c. tube

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36
Q

Oxygenated Process Water Corrosion
solubility of ___increases as the temperature of the water decreases, the corrosion activity due to ____-containing water tends to be higher at lower temperatures.

A

oxygen / oxygen

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37
Q

Oxygenated Process Water Corrosion

affected material? (2)

A

Carbon steel and low-alloy steel

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38
Q

Oxygenated Process Water Corrosion

critical factor? (6)

A

oxygen solubility and content, temperature, and velocity and turbulence/ WATER

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39
Q

Oxygenated Process Water Corrosion

must have?

A

water

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40
Q

Oxygenated Process Water Corrosion

only ___ppm of o2 is needed to increase CR

A

20 ppm

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41
Q

Oxygenated Process Water Corrosion

If a separate water phase is present, oxygenated water corrosion is typically found along the bottom of the _____

A

piping system.

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42
Q

Oxygenated Process Water Corrosion

______ are subject to oxygenated water corrosion because O2 enters vacuum unit systems through leaking

A

Vacuum units

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43
Q

Oxygenated Process Water Corrosion

O2 content less than _____ in non-aerated water systems is very difficult to measure

A

100 ppb

44
Q

Oxygenated Process Water Corrosion
The use of _______ can also be considered for non-aerated systems to reduce O2.However, this is generally not recommended unless vacuum leaks cannot be eliminated.

A

oxygen scavenger injection

45
Q

Oxygenated Process Water Corrosion

appearance? and on low velocity?

A

extensive general pitting on wetted surfaces. Localized pitting occurs in low-velocity areas at reduced temperatures.

46
Q

Microbiologically Induced Corrosion (MIC)

resistant material?

A

Ti

47
Q

Microbiologically Induced Corrosion (MIC)

what type of environment? Occasionally it is found in services where water is ____ present.

A

aqueous / intermittently

48
Q

Microbiologically Induced Corrosion (MIC)

_______flow condition allow and/or promote the growth of microorganisms.

A

stagnant or low flow

49
Q

Microbiologically Induced Corrosion (MIC)
organisms can survive and grow under a wide range of conditions including lack of oxygen, light or dark, high salinity, pH range of ______, and temperatures from _____

A

0 to 12/

0 °F to 235 °F

50
Q

Microbiologically Induced Corrosion (MIC)

all organisms require a source of (3) for growth.

A

carbon, nitrogen, and phosphorous

51
Q

Microbiologically Induced Corrosion (MIC)

A

localized pitting under deposits or tubercles that shield the organism

52
Q

Microbiologically Induced Corrosion (MIC)

appearance?

A

localized pitting under deposits or tubercles that shield the organism

cup-shaped pits within pits (the halo effect) in carbon steel or subsurface cavities in stainless steel.

53
Q

Microbiologically Induced Corrosion (MIC)

what smell indicates MIC?

A

foul smelling

54
Q

Microbiologically Induced Corrosion (MIC)
Proper application of ______ will control, but not eliminate, microbes; therefore, continued treatment is often necessary

A

biocides

55
Q

Microbiologically Induced Corrosion (MIC)

Empty _______ water as soon as possible. Remove moisture and prevent additional moisture intrusion

A

hydrotest

56
Q

Microbiologically Induced Corrosion (MIC)
_____(2) ___ protecting underground structures and interiors of storage tanks have been shown to be effective mitigation methods for MIC.

A

Coating and cathodically

57
Q

Boiler Water Condensate Corrosion

affected material

A

Carbon steel and low-alloy steels

58
Q

Boiler Water Condensate Corrosion

o2 ppm atleast __ to ___ ppm to form a oxide layer

A

3 to 7 ppb

59
Q

Boiler Water Condensate Corrosion

critical factors

A

concentration of dissolved gas (oxygen and/or carbon dioxide), pH, temperature, quality of the feedwater, and the specific feedwater treating system.

60
Q

Boiler Water Condensate Corrosion

appearance? from o2 and co2?

A

Corrosion from oxygen is normally a pitting type damage

Carbon dioxide corrosion is normally smooth, but it can also cause grooving of the pipe wall.

61
Q

CO2 Corrosion

CO2 corrosion results when CO2 dissolves in water to form ____acid

A

carbonic acid (H2CO3)

62
Q 
CO2 Corrosion 
critical factor (2)
A

a. low pH

b. water

63
Q

CO2 Corrosion

appearance (2)

A

b. general or pitting corrosion

64
Q 
CO2 Corrosion 
affected materials (3)
A

a. CS / low alloys

b. SS <12% CR

65
Q

CO2 Corrosion

increasing partial pressure of Co2 = ______pH = increase CR

A

lower

66
Q

CO2 Corrosion

Corrosion usually occurs when the effluent stream drops below the dew point at approximately____F

A

300 °F

67
Q

CO2 Corrosion

It may appear as a number of flat-bottomed pits, sometimes called _____”-type pitting.

A

“mesa

68
Q

CO2 Corrosion

It may appear as a number of _____ pits, sometimes called _____”-type pitting.

A

flat-bottomed / mesa

69
Q

CO2 Corrosion

_____inhibitors can reduce CO2 corrosion in steam condensate system

A

Corrosion

70
Q

CO2 Corrosion

_____inhibitors can reduce CO2 corrosion in steam condensate system

A

Corrosion

71
Q

CO2 Corrosion
inspection?
Monitor _______to determine changes in operating conditions

A

water analyses (pH, Fe, O2, etc.)

72
Q 
Flue Gas Dew Point Corrosion 
At temperatures\_\_\_\_\_\_(2) these gases and the water vapor in the flue gas will condense to form acid
A

at or below the dew point,

73
Q

Flue Gas Dew Point Corrosion
The dew point of sulfuric acid depends on the concentration of sulfur trioxide in the flue gas but is typically about______

A

280 °F (140 °C).

74
Q

Flue Gas Dew Point Corrosion
Dew points for sulfurous, hydrochloric, nitric, and carbonic acids depend on the concentrations of SO2, HCl, NO2, and CO2 and on the water content of the flue gas, but they occur typically at temperatures lower than the water dew point,___________

A

212 °F (100 °C)

75
Q

Flue Gas Dew Point Corrosion
The metallic surfaces at the back end of the boilers and fired heaters and stacks should be kept at least ________ above the dew point temperature of sulfuric acid

A

10 °F (6 °C)

76
Q

Flue Gas Dew Point Corrosion

inspection

A

UT

77
Q

Soil Corrosion

affected material

A

Carbon steel, cast iron, and ductile iron

78
Q

Soil Corrosion

Soil ______is related to the soil moisture content and dissolved electrolytes

A

resistivity

79
Q

Soil Corrosion

Soils having high moisture content, high dissolved salt concentrations, and high acidity are usually the ____corrosive.

A

most

80
Q

Soil Corrosion
_____ areas are often much more susceptible to corrosion than the rest of the structure because of moisture and oxygen availability.

A

Soil-to-air interface

81
Q

Soil Corrosion
appearance
Soil corrosion appears as ________with a roughened surface and localized deeper attack or pitting.

A

external thinning

82
Q

Soil Corrosion
appearance
Soil corrosion appears as ________with a roughened surface and localized deeper attack or pitting.

A

external thinning

83
Q

Soil Corrosion

minimized through the use of appropriate ___(2) __ along with special backfill to prevent rock damage to the coating

A

coatings and cathodic protection

84
Q

Soil Corrosion
A _______survey on a cathodically protected line may be used to verify that the buried piping has a protective potential throughout its length.

A

close-interval potential

85
Q

Brine Corrosion

appearance

A

Widespread or localized pitting

86
Q

Brine Corrosion

________are generally more resistant to pitting in brine solutions than stainless steel and carbon steel

A

Copper alloys

87
Q

Brine Corrosion

_____) piping is immune to this damage mechanism

A

Fiber reinforced plastic (FRP

88
Q

Brine Corrosion

what affect the CR? presence of what?

A

type of salt / H2S

89
Q

Brine Corrosion

appearance for CS /SS

A

Carbon Steel - Heavy scaling and possible tubercles

Stainless Steel – Sharp, deep, isolated pits

90
Q

Brine Corrosion
prevention?
a. Sources of ______ should be identified and eliminated. B. A ______water source should be used for desalter wash water make-up.

A

a. dissolved oxygen

b. deaerated

91
Q

Concentrated Cell Corrosion

Concentration cell corrosion occurs in ______environments.

A

aqueous

92
Q

Concentrated Cell Corrosion

potentially ____aqueous environment must exist

A

corrosive

93
Q

Concentrated Cell Corrosion

appearance for CS /SS

A

CS - Pitting

SS- sharp, narrow, deep pits.

94
Q

Concentrated Cell Corrosion

inspection (2)

A

Vt/ UT

95
Q

Concentrated Cell Corrosion (not a single damage mech but related mechs are )

A

under-deposit corrosion, crevice corrosion, contact point corrosion (also called touch point corrosion), soil/air interface corrosion (see 3.57), and CUI (see 3.22).

96
Q

Concentrated Cell Corrosion (not a single damage mech but related mechs are )

A

under-deposit corrosion, crevice corrosion, contact point corrosion (also called touch point corrosion), soil/air interface corrosion (see 3.57), and CUI (see 3.22).

97
Q

Co2
Corrosion may occur along the bottom surface of a pipe if there is a separate ______or along the top surface of a pipe if condensation in wet gas systems occurs.

A

water phase

98
Q

Co2
Corrosion may occur along the bottom surface of a pipe if there is a separate ______or along the top surface of a pipe if condensation in wet gas systems occurs.

A

water phase

99
Q

Flue Gas Dew Point Corrosion

critical factors? (2)

A

contaminants / operating temperature

100
Q

galvanic corrosion

A

Heat exchangers are susceptible if the tube material is different from the tubesheet and/or baffles

101
Q

CUI

most server at ___ F

A

212

102
Q

Boiler water

Copper/zinc alloys can suffer ___in fresh, brackish and salt water systems.

A

dezincification

103
Q

CO2 affect equipment?

A

Boiler feedwater and condensate systems in all units are affected.

104
Q

CO2 affect equipment?

A

Boiler feedwater and condensate systems in all units are affected.

105
Q

CO2

resistant material?

A

300 SS

106
Q

Fuel Gas

A

All fired process heaters and boilers that burn fuels containing sulfur have the potential for sulfuric acid dewpoint corrosion in the economizer sections

API571 (13 decks)

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