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API571 > module 6 General Damage Mech > Flashcards

module 6 General Damage Mech Flashcards

1
Q

Ammonium Bisulfide Corrosion (Alkaline Sour Water) VL*

NH4HS corrosion occurs from an ammonium salt, formed when ______ and _________ are absorbed in water.

A

Ammonia (NH3

/ Hydrogen Sulfide (H2S)

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2
Q

Ammonium Bisulfide Corrosion (Alkaline Sour Water) VL*
affected material in increasing resistant

………..depending on (2)

A

Primarily Carbon Steel (CS)
• Low-Alloy Steels
• 300 Series SS, duplex SS, nickel-based alloys, and titanium are more resistant,

Ammonium Bisulfide (NH4HS) concentration and velocity.

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3
Q

Ammonium Bisulfide Corrosion (Alkaline Sour Water)VL*

critical factors? (7)

A
  1. NH4HS Concentration
  2. H2S partial pressure
  3. Velocity (Turbulence)
  4. pH
  5. Temperature - It precipitates out of the gas phase below 120°F to 150°F .
  6. Alloy Composition
  7. Flow Distribution (Velocity / Turbulence)
  8. O2 (is bad)
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4
Q

Ammonium Bisulfide Corrosion (Alkaline Sour Water) VL*

Temp It precipitates out of the gas phase range?

A

120°F to 150°F .

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5
Q

Ammonium Bisulfide Corrosion (Alkaline Sour Water)VL*
corrosion increase with _(2)___concentration? below what % is it not corrosive AND for what material ?

NH4HS salts may foul, but will not cause corrosion until _______

A

NH4HS / cyanides

/

2% - CS

/

they get wet (with water).

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6
Q

Ammonium Bisulfide Corrosion (Alkaline Sour Water)VL*

affected equipment?

A

• Primarily Hydroprocessing Units (Hydrotreaters & Hydrocrackers) at the inlet and outlet piping of reactor air coolers (below 150°F [66°C]) – Sour Water
✓ Sour Water Draw Piping – Sour Water
✓ Sour Water Strippers – Overhead & Piping – Sour Water
✓ Amine Units – Overhead Piping & Condensers – Sour Water

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7
Q

Ammonium Bisulfide Corrosion (Alkaline Sour Water)VL*

where is it less likely to be seen and why?

A

• FCCU & Delayed Coker – Fractionator Overhead Condensing Systems - (Sour Water) not as likely as Hydroprocessing units due to concentration

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8
Q

Ammonium Bisulfide Corrosion (Alkaline Sour Water)VL*

appearance at high velocity/ low velocity?

A
  • High Velocity – General loss with the potential for extremely high localized rates. Locating the site of the worst corrosion may be challenge.
  • Low Velocity – Localized under-deposit corrosion if insufficient water is available to dissolve the NH4HS salts
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9
Q

Ammonium Bisulfide Corrosion (Alkaline Sour Water)VL*

•Review Velocities especially when NH4HS concentrations exceed ____ % and approach ____ % or higher.

A

2 wt / 8 wt

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10
Q

Ammonium Bisulfide Corrosion (Alkaline Sour Water)VL*
Use resistant materials of construction (e.g. duplex stainless steel, Alloy 825) at velocities above ________ depending on NH4HS concentration.

A

20 fps,

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11
Q

Ammonium Bisulfide Corrosion (Alkaline Sour Water)VL*

Provide sufficient ________ to ensure that an adequate amount of water remains as liquid to dilute the NH4HS salts

A

excess water

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12
Q

Ammonium Bisulfide Corrosion (Alkaline Sour Water)VL*

a. good design practice symmetrical and hydraulically balances in and out of air cooled exchangers.
b. use proper __(2)____

A

injection spray nozzles and metallurgy

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13
Q

Ammonium Bisulfide Corrosion (Alkaline Sour Water)VL*

inspection method? typical (2), for (CV -1) , for (air cooler /exchanger tube -5)

A
  • UT scanning and/or RT profile.
  • UT downstream of control valves due to increased velocity.
  • IRIS/MFL/NFT/RFT/ECT for air cooler and exchanger bundle tubes
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14
Q

Ammonium Bisulfide Corrosion (Alkaline Sour Water)VL*

a.Ammonium bisulfide corrosion can be________and difficult to locate

A

high localized

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15
Q

Ammonium Bisulfide Corrosion (Alkaline Sour Water)VL*

b. Special attention to _____ location in area of expected water impact
c. Water injection facilities and flow meter to ________(2)

A

water injection

monitor and inspect spray nozzles.

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16
Q 
Ammonium Chloride (NH3Cl ) Corrosion and Amine Hydrochloride (HCL) Corrosion VL*
One way salt can form is by molecules of\_\_\_\_\_\_ gas and \_\_\_\_\_\_\_\_\_\_
A 
Ammonia (NH3)
Hydrogen Chloride (HCl)
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17
Q 
Ammonium Chloride (NH3Cl ) Corrosion and Amine Hydrochloride (HCL) Corrosion VL*
source of CL?
A

A source of Cl is in the hydrogen that is produced by the Catalytic Reformer (they inject it
for catalyst activation).

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18
Q 
Ammonium Chloride (NH3Cl ) Corrosion and Amine Hydrochloride (HCL) Corrosion VL*
NH3 originates with the small amount of nitrogen present in\_\_\_\_
A

oil.

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19
Q 
Ammonium Chloride (NH3Cl ) Corrosion and Amine Hydrochloride (HCL) Corrosion VL*
critical factors (3)
A
  • Concentration (NH3, HCl, or amine salts)
  • Temperature –
  • Water Availability
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20
Q 
Ammonium Chloride (NH3Cl ) Corrosion and Amine Hydrochloride (HCL) Corrosion VL*
wheat temp can ammonium chloride salt precipitate?
A

around 400°F

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21
Q 
Ammonium Chloride (NH3Cl ) Corrosion and Amine Hydrochloride (HCL) Corrosion VL*
What is HYGROSCOPIC ?
A

NH3Cl - absorbs water when there is none

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22
Q 
Ammonium Chloride (NH3Cl ) Corrosion and Amine Hydrochloride (HCL) Corrosion VL*
corrosion rate
A

> 100Mpy

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23
Q 
Ammonium Chloride (NH3Cl ) Corrosion and Amine Hydrochloride (HCL) Corrosion VL*
Ammonium Chloride is very \_\_\_\_\_\_\_\_, highly corrosive, and form an acidic solution when mixed with water
A

water soluble

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24
Q 
Ammonium Chloride (NH3Cl ) Corrosion and Amine Hydrochloride (HCL) Corrosion VL*
\_\_\_\_\_\_\_\_amine can also react with HCL to form amine hydrochlride that can act in a similar fashion.
A

neutraalizing

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25
Q 
Ammonium Chloride (NH3Cl ) Corrosion and Amine Hydrochloride (HCL) Corrosion VL*
affected equipment? (2)
A

a. RX effluent streams and the H2 recycle system are subject ammonium chloride
b. overheads where condensing occurs

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26
Q 
Ammonium Chloride (NH3Cl ) Corrosion and Amine Hydrochloride (HCL) Corrosion VL*
appearance ? (color )
A

whitish , greenish or brownish appears

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27
Q 
Ammonium Chloride (NH3Cl ) Corrosion and Amine Hydrochloride (HCL) Corrosion VL*
may not be evident during ...(NDE)......due to water washing or steam out that remove deposits
A

VT

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28
Q 
Ammonium Chloride (NH3Cl ) Corrosion and Amine Hydrochloride (HCL) Corrosion VL*
prevention in crude units?
A
  • Improve desalting – Operational item.
  • Add caustic to the desalted crude – (caustic reacts with the chlorides to prevent the formation of NH3Cl).
  • Add water wash to contact and dilute the NH3Cl salts.
  • Add neutralizer and filming amines (corrosion inhibitors) to deter the corrosive effects
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29
Q

Ammonium Chloride (NH3Cl ) Corrosion and Amine Hydrochloride (HCL) Corrosion VL*
inspection?
a. ammonium chloride corrosion may be highly _____and difficult to locate.

A

localized

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30
Q 
Ammonium Chloride (NH3Cl ) Corrosion and Amine Hydrochloride (HCL) Corrosion VL*
(3) NDE
A

C. RT/UT

d. Guide wave tech(GWT)

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31
Q 
Ammonium Chloride (NH3Cl ) Corrosion and Amine Hydrochloride (HCL) Corrosion VL*
when is deposit often detected?
A

when pressure drop increase

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32
Q 
Ammonium Chloride (NH3Cl ) Corrosion and Amine Hydrochloride (HCL) Corrosion VL*
related mech (4)
A

HCL acid corrosion

Aqueous organic acid corrosion

Concentration cell corrosion

CL SCC

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33
Q 
Hydrochloric Acid (HCl) Corrosion 
Very aggressive  \_\_\_( 2) \_\_\_\_-
A

general and/or localized corrosion

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34
Q 
Hydrochloric Acid (HCl) Corrosion 
Damage associated with\_\_\_\_\_\_ corrosion of hydrochloric acid.

condense from the overhead stream of a distillation, fractionation or stripping tower.

A

dew point

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35
Q 
Hydrochloric Acid (HCl) Corrosion 
must have \_\_\_\_?
A

WAter

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36
Q 
Hydrochloric Acid (HCl) Corrosion 
The \_\_\_\_\_water (acid) droplets that condense can be highly acidic
A

FIRST

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37
Q 
Hydrochloric Acid (HCl) Corrosion 
affected materials
A

all metals

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38
Q 
Hydrochloric Acid (HCl) Corrosion 
\_\_(2)\_\_\_\_ are not usefully resistant to HCL at any concentration or temp
A

300/400 SS

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39
Q 
Hydrochloric Acid (HCl) Corrosion 
\_\_\_\_\_\_\_(2) \_\_\_\_\_ have GOOD resistance to dilute HCI
A

alloy 400,Ti and other Nickle based alloy

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40
Q 
Hydrochloric Acid (HCl) Corrosion 
\_\_\_\_presensce of what is bad
A

o2

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41
Q 
Hydrochloric Acid (HCl) Corrosion 
critical factor? (3)
A

HCL acid concentration, temp and alloy composition

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42
Q 
Hydrochloric Acid (HCl) Corrosion 
HCL gas is not normally corrosive in \_\_\_\_process streams , but is in \_\_\_\_\_\_
A

dry / wet

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43
Q 
Hydrochloric Acid (HCl) Corrosion 
CS/low alloy are subject to excessive corrosion when pH \_\_\_\_\_\_
A

< 4.5.

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44
Q 
Hydrochloric Acid (HCl) Corrosion 
affected equipment (3)
A

• Crude Tower – Overhead condensers. It’s a problem in the Vacuum condensers too.
• Hydroprocessing – Chlorides may enter the unit with the feed or with the hydrogen.
• Catalytic Reforming – Chlorides are ADDED to the catalyst for activation. As time goes on, it
is stripped off and sent downstream through the recovery section.

A byproduct of the reforming reaction is hydrogen, which is collected and sent to
Hydroprocessing Units. This hydrogen stream may also contain stripped chlorides.

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45
Q 
Hydrochloric Acid (HCl) Corrosion 
1. appearance for CS/ low alloy    &  SS
A

a. CS and Low-Alloy Steels - General Thinning, Localized Corrosion or Under-Deposit
Attack.
b. 300 Series SS and 400 Series SS - suffer pitting attack. 300 Series SS can also experience Cl SSC (depending on the temperature)

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46
Q 
Hydrochloric Acid (HCl) Corrosion 
prevention at Crude Units: (5)
A

• Improve desalting – Operational item.
• Add caustic to the desalted crude – (caustic reacts with the chlorides to prevent the
formation of NH3Cl).
• Add water wash to contact and dilute the NH3Cl salts.
• Add neutralizer and filming amines (corrosion inhibitors) to deter the corrosive effects.
-Monitor locations for chlorinee contents

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47
Q 
Hydrochloric Acid (HCl) Corrosion 
prevention at hydro processing (2)
A
  • Limit chlorides in the M/U H2.

* Use water wash in the reactor effluent to flush/neutralize

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48
Q 
Hydrochloric Acid (HCl) Corrosion 
prevention at Catalytic Reforming, Crude Units, Hydro processing (2)
A

➢ Use a water wash in the reactor effluent to flush/neutralize.
➢ Add a filming amine and/or neutralizer

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49
Q 
Hydrochloric Acid (HCl) Corrosion 
related mech
A

Amonnum chloride

CL SCC

Aqueous organic acid corrosion

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50
Q

Hydrofluoric (HF) Corrosion

appearance?

A

general/localized corrosion

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51
Q

Hydrofluoric (HF) Corrosion
material generally not suitable?

suitable?

A

300/400/low alloy /

CS / Copper ni, alloy 400

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52
Q

Hydrofluoric (HF) Corrosion

material use in some application

A

nickle based alloy such as alloy c276 is used in some applications

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53
Q

Hydrofluoric (HF) Corrosion

critical factor

A

water content), temperature, alloy composition, presence of contaminants including oxygen and sulfur compounds are the controlling factors

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54
Q

Hydrofluoric (HF) Corrosion

__(2)____will remove the protective fluoride scale layer.

A

Water & velocity

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55
Q

Hydrofluoric (HF) Corrosion

Corrosion rates __increase_____as HF concentrations ____and temp ____

A

decrease / increase

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56
Q

Hydrofluoric (HF) Corrosion

Water content in HF, at >_____ % in acid increases corrosion rates.

A

1.5 wt

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57
Q

Hydrofluoric (HF) Corrosion

CS operating above________. Higher temperatures can increase corrosion rates.

A

150 °F (65 °C)

58
Q

Hydrofluoric (HF) Corrosion

In CS, the Residual Element (RE) content should be ___%

A

0.20%

59
Q

Hydrofluoric (HF) Corrosion

_____ hF have a very low general CR in CS

A

dry , fresh

60
Q

Hydrofluoric (HF) Corrosion

______phase change in azeotropic will cause localized corrosion of CS.

A

rich HF

61
Q

Hydrofluoric (HF) Corrosion

Preheating rich HF > 160F require what material?

A

alloy 400

62
Q

Hydrofluoric (HF) Corrosion

high CR on piping/equipment______F

A

> 150F

63
Q

Hydrofluoric (HF) Corrosion

appearance in CS

A

CS – Local or general corrosion

64
Q

Hydrofluoric (HF) Corrosion

what material will scale? and not?

A

CS / Alloy 400

65
Q

Hydrofluoric (HF) Corrosion

Alloy 400 appearance

A

may thin

66
Q

Hydrofluoric (HF) Corrosion

Non PWHT Alloy 400 is susceptible to_____ when in the presence of wet HF & O2

A

SCC

67
Q

Hydrofluoric (HF) Corrosion

______reduce problems associated with SOHIC

A

PWHT reduce problems associated with SOHIC

68
Q

Hydrofluoric (HF) Corrosion

_______can be use to eliminate problem associate with blistering, HIC or SOHIC

A

Alloy 400

69
Q

Hydrofluoric (HF) Corrosion

What content can be monitor with AP751?

A

RE content of CS

70
Q

Hydrofluoric (HF) Corrosion

related mech

A

• Hydrogen stress cracking in HF acid (3.41), hydrogen blistering and HIC/SOHIC, HF

71
Q

Naphthenic Acid Corrosion

primarily temp range? and as low as?

A

425 - 750°F range.

350F

72
Q

Naphthenic Acid Corrosion

where nap comes from?

A

some crude oil

73
Q

Naphthenic Acid Corrosion

affected materail?

A

CS, Low-Alloy Steels, 300 SS, 400 SS, and Nickel-Based alloys - almost all the same

74
Q

Naphthenic Acid Corrosion

NAC is not reduced by ___(like sulfidation), but it is resistant to______and at what %?

A

Chrome / Molybdenum (2-2.5%)

75
Q

Naphthenic Acid Corrosion

NAC appears in ____hydrocarbon steam that _____contain a free water phase.

A

hot dry / DO NOT

76
Q

Naphthenic Acid Corrosion
TAN may be misleading because this family of acids has a range of boiling points and tends to concentrate in various cuts. Therefore, NAC is determined by the _______ of the actual
stream not the crude charge.

A

acidity

77
Q

Naphthenic Acid Corrosion

critical factor? (5)

A
  • Naphthenic Acid concentration
  • Temperature
  • Velocity
  • Sulfur Content (the more the better)
  • Alloy Composition
78
Q

Naphthenic Acid Corrosion

critical factor? (5)

A
  • Naphthenic Acid concentration
  • Temperature
  • Velocity
  • Sulfur Content (the more the better)
  • Alloy Composition
79
Q

Naphthenic Acid Corrosion

affected equipment? (2)

A
  • Crude and Vacuum heater tubes/transfer lines.

* Piping systems are susceptible in areas of high velocity

80
Q

Naphthenic Acid Corrosion

appearance? general? high / low velocity?

A
  • NAC is characterized by localized corrosion, pitting, or flow induced grooving in high-velocity areas.
  • In low-velocity condensing conditions, it shows up as uniform loss and/or pitting.
81
Q

Naphthenic Acid Corrosion

At temperatures below ____, NAC can have a smoother, more uniform appearance than is typical at higher temperatures.

A

~450°F (230°C)

82
Q

Naphthenic Acid Corrosion

what alloys to use and have resistance? and material #?

A

Use alloys with higher molybdenum content for improved resistance (317L is common).

83
Q

Naphthenic Acid Corrosion

Use ___-chemical inhibit to reduce NAC ? and how else to reduce __2___?

A

Use NAC chemical inhibitors.

• NAC can be reduce by blending crude and/or increase sulfer content

84
Q

Naphthenic Acid Corrosion

Use ___-chemical inhibit to reduce NAC ? and how else to reduce __2___?

A

Use NAC chemical inhibitors.

• NAC can be reduce by blending crude and/or increase sulfer content

85
Q

Naphthenic Acid Corrosion

NDE?

A

UT/RT

86
Q

Naphthenic Acid Corrosion

NDE?

A

UT/RT

87
Q

Aqueous Organic Acid Corrosion

description?

A

Organic compounds present in some crude oils decompose in the crude furnace to form low molecular weight organic acids.

88
Q

Aqueous Organic Acid Corrosion

affected material?

A

Carbon steel and low-alloy steels.

89
Q

Aqueous Organic Acid Corrosion

What MW acid more corrosive ? name 4?

A

low MW acids

formic , acetic, propionic, butric

90
Q

Aqueous Organic Acid Corrosion

one source of these acids is believe to be the _________ of nap acids .

A

thermal decomposition

91
Q 
Aqueous Organic Acid Corrosion 
affected equipment (2)
A
  • Crude tower overhead system
  • Vacuum tower overhead system
  • Coker Fractionator overhead system
92
Q 
Aqueous Organic Acid Corrosion 
affected equipment (3)
A
  • Crude tower overhead system
  • Vacuum tower overhead system
  • Coker Fractionator overhead system
93
Q

Aqueous Organic Acid Corrosion

prevention (4)

A

• Neutralize
• Use filming amine
• Use corrosion resistant alloys
-blend crude to not have Nap / Tan

94
Q

Aqueous Organic Acid Corrosion

inspection? (3)

A
  • UT & RT
  • Monitor process water for pH
  • Use corrosion probes and/or corrosion coupons
95
Q

Aqueous Organic Acid Corrosion

• It is difficult to distinguish between these Organic acids and____

A

HCl acid

96
Q

Aqueous Organic Acid Corrosion

• It is difficult to distinguish between these Organic acids and____

A

HCl acid

97
Q

Phenol (Carbolic Acid) Corrosion **NL

when is phenol used?

A

used as a solvent to remove aromatic compounds from lubricating oil.

98
Q

Phenol (Carbolic Acid) Corrosion **NL

increasing resistance material?

A

-CS , 304L, 316L and alloy C276

99
Q

Phenol (Carbolic Acid) Corrosion **NL

critical factor? (4)

A

Temperature, Water Content, Alloy Chemistry and, Flow Velocity.

100
Q

Phenol (Carbolic Acid) Corrosion **NL

dilute aqueous solutions______ can be very corrosive

A

(5-15% phenol

101
Q

Phosphoric Acid Corrosion (NL)

Phosphoric acid is used as a _______in _______units.

A

catalyst / polymerization

102
Q

Phosphoric Acid Corrosion (NL)

where does it most often occur?

A

Most corrosion probably occurs during water-washing operations at shutdowns

103
Q

Phosphoric Acid Corrosion (NL)

Solid phosphoric acid catalysts are not corrosive to ____…unless _______ is present.

A

CS / unless free water is present

104
Q

Sour Water Corrosion (Acidic) -

is to due to ___ and ___ in SW

A

H2s and NH3

105
Q

Sour Water Corrosion (Acidic) -

pH between?

A

4.5 - 7

106
Q

Sour Water Corrosion (Acidic) -

affected material

A

CS

107
Q 
Sour Water Corrosion (Acidic) - 
critical factor (5)
A
  • H2S Concentration - H2S Partial Pressure
  • Ph - pH between 4.5 and 7.0
  • Temperature - H2S concentration in the sour water decreases as temperature increases.
  • Velocity - High velocity removes the protective iron sulfide layer.
  • Oxygen content – Bad!
108
Q

Sour Water Corrosion (Acidic) -

as ____concentrations decrease pH to about _______

A

H2S / 4.5

109
Q

Sour Water Corrosion (Acidic) -
H2S concentration
1. in the sour water decreases as temperature _____.
2. increase h2s _____pH

A

increases
/
decrease

110
Q

Sour Water Corrosion (Acidic) -

affected equipment?

A

• Acid sour water corrosion is a concern in overhead systems of FCCU and Coker gas fractionation plants with high levels of H2S and low NH3 level

111
Q

Sour Water Corrosion (Acidic) -

prevention

A

process monitor and control.

112
Q

Sulfuric Acid Corrosion * (VL)

In order of increasing resistance:

A

CS, 316L SS, Alloy 20, high-silicon cast iron, high-nickel cast iron, Alloy B-2, and Alloy C-276

113
Q 
Sulfuric Acid Corrosion * (VL)
critical factor (5)
A
  • Acid Concentration – Acid concentration below 65% causes extensive corrosion for CS.
  • Temperature – The colder the better.
  • Alloy Content
  • Velocity – CR increase if velocity >2-3 fps.
  • Contamination and presence of oxidizers (oxygen)
114
Q

Sulfuric Acid Corrosion * (VL)

Acid concentration below ___%causes extensive corrosion for CS.

A

65%

115
Q

Sulfuric Acid Corrosion * (VL)

temp that better

A

colder

116
Q

Sulfuric Acid Corrosion * (VL)

velocity range when CR increase?

A

> 2-3 fps

increase significantly

117
Q 
Sulfuric Acid Corrosion * (VL)
Affected equipment (2)
A
  • Sulfuric acid units and waste water treatment plants are affected.
  • Water mix points cause heat and dilutes caustic so corrosion increases.
118
Q

Sulfuric Acid Corrosion * (VL)

best (3) material?

A

a. Use alloys that are more resistant such as Alloy 20,904L, C276

119
Q

Sulfuric Acid Corrosion * (VL)

NDE (2)

A

UT / RT suspected areas

120
Q

Ammonia Chloride

not normal to be affected by ammonium chloride corrosion?

A

Sulfuric acid units caustic regenerators

121
Q

Ammonia Chloride

Best effective NDE?

A

RT/UT

122
Q

Hydrochloric Acid (HCl) Corrosion

The presence of oxidizing agents (oxygen, ferric and cupric ions) will increase the corrosion rate,
particularly for alloy 400 and Alloy B-2. Titanium performs well in oxidizing conditions but fails rapidly in ________HCl service.

A

dry

123
Q

Hydrofluoric (HF) Corrosion
Severe fouling due to iron ____corrosion product has been observed in the piping, heat exchangers and in the tops of the Isostripper and Depropanizer towers

A

fluoride

124
Q

Hydrofluoric (HF) Corrosion
Corrosion can be prevented by careful operation of the unit to minimize ___(3) ____and other
contaminants in the feed

A

water, oxygen, sulfur

125
Q

NAC
A form of _____temperature corrosion that occurs primarily in ___(2)____, and downstream units that process certain fractions or cuts that contain naphthenic acids.

A

high

crude and vacuum units

126
Q

Phenol (Carbolic Acid) Corrosion **NL

Carbon steel and 304/304L stainless steel corrode rapidly in phenol service above ___°F (232o C).

A

450

127
Q

Phenol (Carbolic Acid) Corrosion **NL

Corrosion will be in the form of______corrosion of carbon steel.

A

general or localized /

erosion corrosion

128
Q

Phosphoric Acid Corrosion (NL)
It can cause both ______corrosion
and _____corrosion of carbon steels depending on water content.

A

pitting / localized

129
Q

Phosphoric Acid Corrosion (NL)
Solid phosphoric acid catalysts are not corrosive to carbon steel unless ____ is present. When
water is present, _____corrosion of carbon steel may occur.

A

free water / severe

130
Q

Phosphoric Acid Corrosion (NL)

Corrosion rates increase with ____temperature.

A

increasing

131
Q

Phosphoric Acid Corrosion (NL)

Corrosion can penetrate a 1/4-inch thick steel tube in ____hours

A

eight

132
Q

Phosphoric Acid Corrosion (NL)
Corrosion is usually found in ______velocity areas where there is little or no circulation such as piping manifolds, the bottom of kettle-type reboilers, partial penetration welds, and exchangers where there is sufficient residence time to permit the settling of acid droplets.

A

low

133
Q

Sour Water Corrosion (Acidic) -

The presence of ____or oxidants may increase the corrosion and usually produces pitting or underdeposit attacks.

A

air

134
Q

Sour Water Corrosion (Acidic) -
300 Series SS can be used at temperatures below about _____(60o C) where Chloride Stress Corrosion Cracking (CSCC) is not likely.

A

140F

135
Q

Sour Water Corrosion (Acidic) -
In some instances at a pH above 4.5, a thicker, porous sulfide film layer can form. This can promote ____under sulfide deposits.

A

pitting

136
Q

Sulfuric Acid Corrosion * (VL)
Sulfuric acid promotes ____and ____corrosion of carbon steel and other alloys. Carbon steel _______may experience severe corrosion.

A

general / localized

HAZ

137
Q

Sulfuric Acid Corrosion * (VL)

Mix points with water cause ______to be released and high corrosion rates can occur where the acid becomes diluted.

A

heat

138
Q

Sulfuric Acid Corrosion * (VL)

Mostly general in nature, but attacks carbon steel _________ rapidly.

A

weld heat affected zones

139
Q

Sulfuric Acid Corrosion * (VL)

Sulfuric acid attacks ____left from welding.

A

slag

140
Q

Sulfuric Acid Corrosion * (VL)

Acidified product streams can be washed with caustic to ____the acid.

A

neutralize

141
Q

Sulfuric Acid Corrosion * (VL)
Corrosion of steel by dilute acid is usually in the form of overall metal loss or pitting and becomes more severe with increasing ___(2)___

A

temperature and velocity.

API571 (13 decks)

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