API-RP-571-Damag-10

API RP 571 - Damage Mechanisms Spreadsheet

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Damage Mechanisms Description of Damage Temperature Range Affected Materials Prevention Inspection

Graphitization Some grades of CS and 0.5Mo steels Addition of 0.7% Cr Full thickness sample metallography

Softening (Spheroidization) CS and low alloys Minimize exposure to elevated temps

Temper Embrittlement

Strain Aging Intermediate Temperature None

885°F Embrittlement 600°F - 1000°F

Sigma Phase Embrittlement 1000°F - 1750°F

Brittle Fracture

It is a change in the microstructure of certin carbon steels and 0.5 Mo steels after long term operation in the 800 to 1100 F range may cause a loss in strength, ductility and/or creep resistance.

800°F - 1100°F; Graphitization before Spheroidization < 1025°F

May cause a loss in strength and/or creep resistance.

850°F - 1400°F; Spheroidization before Graphitization > 1025°F

May Cause a loss in strength and or creep resistance.

Field metallography or removal of samples

reduction in toughness. This change causes an upward shift in the ductile-to-brittle transition temperature. (by Charpy impact testing)

650°F - 1100°F; Quicker at 900°F but more severe in long-term

exposure at 850°F

Primarily 2.25Cr; Older 2.25Cr manuf. prior to 1972 particularly susceptible

Pressurization sequence - MPT of 350°F for older steels and 150°F newer; Heat treat to 1150°F and cool rapidly for temporary reverse; Limit J and X factors.

Impact test sample blocks from original heat

found in most older vintage steels and 0-0.5 Mo low alloy steels under the combined effects of deformation and aging at an intermediate temperature. This results in an increase in hardness and strength with a reduction in ductility and toughness

Mostly pre-1980’s carbon steels with large grain size and C-0.5 Mo low

alloy steel

No issue for newer steels with enough Al for deoxidizer; BOF better than older Bessemer; Pressurization sequence;

PWHT or "Butter"

is a loss in toughness due to a metallurgical change that occurs in alloys containing a ferrite phase, as a result of exposure in the temeratur range 600 to 1100.

Alloys containing a ferrite phase; 400 SS and Duplex SS

Use low ferrite or non-ferritic alloys; Heat treat to 1100°F and cool rapidly

Impact/bend test samples; Cracking during t/a or when below 200°F;

Increase in hardness

Ferritic, martensitic, austenitic, and duplex SS

SS with sigma may have lack of toughness below 500°F; Minimize weld metal ferrite content; Solution anneal at

1950°F and water quench to reverse

Testing of samples; Cracking during t/a or when below 500°F

Temperatures below ductile-to-brittle transition temp

CS and low alloys esp. prior to 1987; 400 SS also susceptible

Material selection; Minimize pressure at ambient temperatures; PWHT; "Warm"

pre-stress hydrotest

None to minimize; Susceptible vessels inspect for pre-existing flaws


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Creep and Stress Rupture All metals and alloys

Thermal Fatigue Temp swings exceeding 200°F All materials of construction VT, MT/PT, SWUT for cracking

Steam Blanketing Short-term, high-temp failures. CS and low alloys

> 510°F

Thermal Shock All metals and alloys

Erosion/Erosion – Corrosion N/A All metals, alloys and refractories

Cavitation

Mechanical Fatigue N/A

Vibration-Induced Fatigue N/A All engineering materials Visual/Audible signs of vibration

Refractory Degradation N/A Refractory materials Selection; Design; Installation VT during shutdown; IR online

Reheat Cracking

Galvanic Corrosion N/A Visual and UT Thickness

Atmospheric Corrosion CS, low alloys, and copper alloyed Al Surface prep and proper coating VT and UT

CS, low alloys, 300 SS and duplex SS Strip insulation; VT, UT, IR, etc.

SEE Table 4-2 for Threshold Temp:

C.S. --> 700ºF C-1/2 Mo --> 750ºF

1.25Cr thru 9Cr --> 800ºF 304H --> 900ºF

347H --> 1000ºF

Minimize temperatures; Higher PWHT may help; Minimize hot spots in heaters

Combination of techniques; Tubes bulging, sagging, diametric growth

Design and operation; Liner to prevent cold liquid from contacting hot surface

Short Term Overheating – Stress Rupture

Local overheating above design temperature

All fired heater tube materials and common materials of construction

Minimize temperature excursions; Burner management

Visual; IR monitoring; Tubeskin thermocouples

Tube rupture quickly follows DNB; Burner management; BFW treatment

Visual for bulging on tubes and burners

Dissimilar Metal Weld (DMW) Cracking

Widely differing thermal expansion coefficients; Most common CS to

Austenitic SS

Ni based fillers; 300 SS rods used in low temp location only; Pup piece with

intermediate coefficient

Visual and MT/PT for OD cracks; UT for ID cracks

Significant Temperature Differentials

Minimize flow interruptions, severe restraint, rain/fire water deluge; Review

injection points; Thermal sleeves

Highly localized; MT/PT to confirm cracking only

Design; Erosion - harder alloys; Corrosion - corrosion resistant alloys;

Impingement plates; Tube ferrules

VT, UT, RT; Corrosion coupons; IR scans for refractory

More likely at temps approaching the boiling point of the liquid

Most common materials of construction

Mechanical, design, or operational change; Sufficient NPSH; Streamline

flow; Remove air; Decrease velocities; Fluid additives

Accoustic monitoring; Pumps may sound like pebbles being thrashed

around; VT, UT, RT for loss of thickness

All alloys; Stress levels and number of cycles to failure vary by material

Good design; Material selection; Minimize stress risers

MT, PT, SWUT for cracks; Vibration monitoring

Design; Supports and vibration dampeners; Stiffeners on small bore;

Branch sizing

During PWHT or at elevated temps.

low alloys, 300 SS, and Ni base alloys; High Strength Low Alloys

(HSLA)

Joint configurations in heavy walls; Minimize stress risers

UT and MT/PT for surface cracks; UT for embedded cracks

All metals with the exception of most noble metals; SEE Table 4-4 for

Galvanic Series

Design; Differing alloys not in intimate contact; Coatings

Corrosion rates increase with temp up to about 250°F.

Corrosion Under Insulation (CUI)

More severe 212°F - 250°F for CS

Selection of insulation type; Maintain coatings and insulation


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Cooling Water Corrosion

N/A

CS and low alloys VT, UT, RT

CS, low alloys and 300 SS UT for wall loss; VT and PT for SCC

Soil Corrosion

Caustic Corrosion Primarily CS, low alloys and 300 SS

Dealloying N/A

Graphitic Corrosion

Oxidation

Sulfidation > 500°F

Carburization > 1100°F

Decarburization Elevated temperatures CS and low alloys

Metal Dusting 900°F - 1500°F

Process side > 140°F; Brackish and salt water outlet > 115°F

CS, all grades of SS, copper, Al, titanium and Ni base alloys

Design process inlet < 135°F; Operation; Chemical treatment; Maintain

water velocities; Avoid ERW tubes

pH; Oxygen content; Outlet temps; EC/IRIS tubes

Boiler Water Condensate Corrosion

Primarily CS; Some low alloy, 300 SS and copper based alloys

Oxygen scavenging treatment; Amine inhibitor treatment

Water analysis; Dearator cracking WFMT

CO2 CorrosionIncreasing corrosion with

increasing temp up to dewpoint < 300°F

Cr > 12% (SS); Corrosion inhibitors; Increase pH > 6; Operation problems;

400 SS and Duplex SS resistant; Water analysis

Flue-Gas Dew-Point Corrosion

Sulfuric acid dewpoint < 280°F; Hydrochloric acid dewpoint <

130°F; pH < 6

Maintain temps > 280°F; Avoid 300 SS if chlorides present; Soda Ash wash to

neutralize the acids

Microbiologically Induced Corrosion (MIC)

0°F to 235°F; pH range 0 - 12 (Any)

Most common materials of construction

Treat water with biocides; Maintain flow velocities; Empty hydrotest water;

Maintain coatings

VT; Measure biocide residual; Operating conditions indicate fouling;

Foul smelling water

Corrosion rates increase with increasing metal temperature

Carbon steel, cast iron, and ductile iron

Most effective coatings and cathodic protection; Special backfill may help to

lesser degree

Structure to soil potential; Soil resistivity; VT, guided UT, Pressure

testing

High solution strength caustic general corrosion of CS above 175°F and very high CRates

above 200°F.

Design; Adequate water flooding; Burner management; Dilution of caustic

UT Scans, RT, Injection points, Boroscope steam generating

equipment

Primarily copper alloys as well as Alloy 400 and cast iron

Difficult to predict; Addition of alloying elements may help; CP or coatings may

help

VT (may change color but may require scale removal), Metallography, Loss of

"metallic ring"

< 200°F in the presence of moisture or an aqueous phase

Primarily gray cast iron, but also nodular and malleable cast irons

which tend to crumble when attacked

Difficult to predict; Internal coatings/cement linings for internal

graphitic corrosion; external coatings or CP in corrosive soils

Loss of "metallic ring"; Reduction in hardness

Oxidation of CS significant > 1000°F;

300 Series SS susceptible to scaling > 1500°F.

SEE Table 4-6 for CR at elev. Temps

CS and low alloys; All 300 SS, 400 SS and Ni base alloys oxidize to

varying degrees

Upgrade alloy; Addition of Cr primary element for oxidation resistance

Monitor process conditions and temperatures; UT for thickness loss

CS, low alloys, 300 SS and 400 SS; Ni base alloys to varying degrees depending on Cr content; Copper

base alloys at lower temps than CS

Upgrade to higher Cr; Al diffusion treatment of low alloys may reduce but

not completely protect

Monitor process conditions and temperatures; UT for thickness loss;

Proactive and retroactive PMI

CS and low alloys, 300 SS and 400 SS, cast SS, Ni base alloys with

significant Fe content and HK/HP alloys

Alloy selection (Si & Al oxidizers); Lower temperatures and higher oxygen/sulfur

partial pressures.

Hardness/Field metallography if process side accessible; RT, UT, MT

for cracking in advanced stages

Control chemistry of gas phase; Cr and Mo form more stable carbides

Field metallography; Hardness tests for softening

All; No known alloy immune under all conditions

Protective layer of sulfur (usually as H2S); Material selection for specific application; Al diffusion treatment

Compression wave UT for heater tubes; RT for pitting/thinning; VT if ID

is accessible


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Fuel Ash Corrosion VT; UT for loss of thickness

Nitriding > 600°F; Severe > 900°F Alloy change to 30% - 80% Ni

> 140°F

Corrosion Fatigue N/A All metals and alloys UT, MT

Any temperature

N/A Many commonly used materials

Amine Corrosion Primarily CS; 300 SS highly resistant

< 150°F

Metal temps above the melting point of liquid species:

Oil ash - melting points below 1000°F possible; Waterwall

corrosion - melting points 700°F; Coal ash - melting points 1030°F

to 1130°F

All conventional alloys for process heaters and boilers; 50Cr-50Ni family

show improved resistance

Blend or change fuel source; Burner design/management; Low excess

oxygen; Alloy upgrade to 50Cr-50Ni for hangers/supports

Carbon steels, low alloys, 300 SS and 400 SS; Ni based alloys more

resistant

Change in color to dull gray; Hardness testing (400 - 500 BHN); Check 300 SS for magnetism; Metallography; ECT; PT, RT, or UT for cracking in

advanced stages

Chloride Stress Corrosion Cracking (Cl-SCC)

300 SS; Ni 8% - 12% most susceptible; Ni > 35% highly resistant,

Ni > 45% nearly immune

Material selection; Low chloride water for hydrotest; Coatings under insulation;

Avoid designs with stagnant areas where chlorides can concentrate

VT in some cases, PT (surface prep may be necessary), ECT, UT

Reduce corrosion (inhibitors, material selection, coatings, BFW chemical

control, etc.); PWHT; Controlled start-up (thermal expansion)

Caustic Stress Corrosion Cracking (Caustic

Embrittlement)

Increasing temps increase likelihood and severity

CS, low alloys and 300 SS; Ni base alloys more resistant.

PWHT at 1150°F for CS; Alloy upgrade to Ni based alloys; Design/operation of

injection system; Water wash equipment prior to steamout

WFMT, EC, RT, ACFM for crack detection; PT not effective (tight,

scale-filled cracks); SWUT for crack depth

Ammonia Stress Corrosion Cracking

Copper alloys with aqueous ammonia and/or ammonium compounds; CS in

anhydrous ammonia

Copper - zinc content below 15%, 90-10CuNi and 70-30CuNi nearly immune, prevent ingress of air, upgrade to 300

SS or Ni alloys; CS - PWHT or addition water (0.2%), weld < 225 BHN, prevent

ingress of oxygen

Copper - monitor pH, ECT or VT on tubes for cracking; CS - WFMT, AET,

or External SWUT

Liquid Metal Embrittlement (LME)

Keep metal with low melting point away from other metal; Grind out cracks not

acceptable

MT or PT for cracks, RT for mercury deposits inside tubes

Hydrogen Embrittlement (HE)

Ambient - 300°F; Decreases with increasing temp; Not likely to occur above 160°F to 180°F

CS, low alloys, 400 SS, Precipitation Hardenable SS, some high strength

Ni base alloys.

Use lower strength steels; PWHT; Low hydrogen, dry electrodes, and preheat

for welding; Bake out at 400°F or higher; Controlled pressurization sequence;

Protective lining, SS cladding, or weld overlay

MT or PT for surface cracks; UT may be helpful; RT not sensitive enough

Increases with increasing temps; Above 220°F can result in acid

gas flashing and severe localized corrosion

Proper operation; Avoid buildup of HSAS; Design should control local pressure drop to minimize flashing;

Avoid oxygen inleakage; Remove solids and hydrocarbons; Corrosion inhibibitors

VT and UT thickness internal; UT scans or profile RT for external;

Corrosion coupons

Ammonium Bisulfide Corrosion (Alkaline Sour

Water)

CS; 300 SS, duplex SS, Al alloys and Ni base alloys more resistant

Symmetrical/balanced flow in and out of air cooled exchangers; Maintain

velocities 10 to 20 fps for CS, resistant materials > 20 fps; Water wash injection

and low oxygen

Frequent UT and RT profile thickness; IRIS and ECT tubes; Monitor water

injection

Ammonium Chloride Corrosion

< 300°F; May corrode well above water dewpoint of 300°F

All commonly used materials; Order of increasing resistance: CS, low

alloys, 300 SS, Alloys 400, duplex SS, 800, and 825, Alloys 625 and

C276 and titanium.

Pitting resistant alloys more have improved resistance; Limit chlorides;

Water wash; Filming inhibitors

RT or UT Thickness; Monitor feed streams; Corrosion coupons may be helpful if salts deposit on the element


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All common materials of construction

> 500°F

Phosphoric Acid Corrosion N/A

N/A

Sulfuric Acid Corrosion N/A

N/A CS and low alloys

CS and low alloys

Aqueous HF environments CS and low alloys WFMT for cracks; Hardness testing

CS and low alloys

Hydrochloric Acid (HCl) Corrosion

Increases with increasing temp up to point where water

vaporizes

Upgrade CS to Ni base can help; Remove chlorides (neutralize, water

wash, absorb, etc.); Minimize carryover of water and salts

AUT or RT for thickness; Corrosion coupons; Check pH

High Temp H2/H2S CorrosionOrder of increasing resistance: CS,

low alloys, 400 SS, and 300 SS

Use alloys with high chromium content; 300 SS are highly resistant at service

temps

UT, VT and RT for thickness; Verify operating temps; Check process H2S

levels periodically

Hydrofluoric (HF) Acid Corrosion

Increase with increasing temp; High CRates observed > 150°F

Low alloys, 300 SS and 400 SS are generally not suitable; CS, Cu-Ni

alloys, Alloy 400, an other Ni base alloys have been used in some

applications

Monitor CS operating > 150°F for thickness; Minimize water, oxygen,

sulfur and other contaminants in feed; Alloy 400 (solid or clad) used to

eliminate blistering/HIC/SOHIC. PWHT to minimize possibility of SCC.

RT or UT Thickness; Monitor small bore piping, flange face corrosion,

blistering/HIC/SOHIC

Naphthenic Acid Corrosion (NAC)

425°F - 750°F; Has been reported from 350°F - 800°F

CS, low alloys, 300 SS, 400 SS, and Ni base alloys

2% - 2.5% molybdenum shows improved resistance; Change or blend

crudes; Inhibitors

RT or UT Thickness; Monitor TAN, sulfur, Fe, and Ni contents

Phenol (Carbolic Acid) Corrosion

Minimal below 250°F; Rapid CRates above 450°F

Order of increasing resistance: CS, 304L, 316L and Alloy C276

Material selection; Velocity < 30 fps; Recovery ovhd temps at least 30°F >

dew point

RT or UT Thickness; Corrosion coupons

Order of increasing resistance: CS, 304L SS, 316L SS, and Alloy 20

304L satisfactory for concentration 100% and temp < 120°F ; 316L required

120°F - 225°F; 316L and Alloy 20 effective at concentrations up to 85% at

boiling temps

RT or UT Thickness; Sample Iron in water; Corrosion coupons

Sour Water Corrosion (Acidic)

Primarily CS; SS, Cu alloys, and Ni base alloys usually resistant

Material selection; 300 SS < 140°F; Cu and Ni resistant, but Cu vulnerable in

ammonia

RT or UT Thickness; Monitor pH of ovhd accumulators; Corrosion

coupons

Order of increasing resistance: CS, 316L, Alloy 20, high Si cast iron, high Ni cast iron, Alloy B-2 and Alloy C276

Materials selection; Proper operation; Caustic wash to neutralize

UT or RT of turbulent zones and hottest areas; Corrosion coupons

Polythionic Acid Stress Corrosion Cracking (PASCC)

Sensitization occurs 750°F - 1500°F

Sensitized austenitic SS; 300 SS, Alloy 600/600H, and Alloy 800/800H

Material selection; Flush with alkaline or soda ash to neutralize or purge with nitrogen or nitrogen/ammonia; Keep

firebox above dewpoint; Heat treatment at 1650°F

Flapper disc sanding to remove deposits and PT

Amine Stress Corrosion Cracking

PWHT all CS welds; Material selection (clad or solid); Water wash non-PWHT CS prior to welding, heat treatment or

steam out

Crack detection best with WFMT or ACFM; PT usually not effective; SWUT

crack depths; AET

Wet H2S Damage (Blistering/HIC/SOHIC/SSC)

Blistering, HIC, and SOHIC ambient to 300°F or higher; SSC

< 180°F

Coatings or alloy cladding; Water wash to dilute HCN or inject ammonium

polysulfide's to convert to thiocyanates; HIC-resistant steels; PWHT can prevent

SSC and help with SOHIC; Inhibitors

Monitor free water phase; Crack detection best with WFMT, EC, RT or ACFM; SWUT for crack sizing; AET

Hydrogen Stress Cracking - HF

PWHT; Weld hardness < 200 HB and no localized zones > 237 HB; CS with Carbon Equivalent < 0.43; B7M Bolts;

Coatings or alloy cladding

Carbonate Stress Corrosion Cracking

Generally no temperature ranges; However, > 200°F if CO2

> 2% in gas scrubbing units

PWHT at 1150°F; Material selection; Coatings or alloy cladding; Water wash

non-PWHT prior to steamout or heat treatment; Inhibitors

Monitoring of pH and CO3-2

concentration; WFMT or ACFM for crack detection; SWUT for crack

depth; AET


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Titanium Hydriding > 165°F Titanium alloys ECT; Metallography; Crush/Bend test

High Temperature Hydrogen Attack (HTHA)

Exposure to hydrogen at elevated temperatures

Order of increasing resistance: CS, C-0.5Mo, Mn-0.5Mo, 1Cr, 1.25Cr,

2.25Cr-1Mo, 2.25Cr-1Mo-V, 3Cr, 5Cr

Alloys with Cr (> 5 Cr) and Mo or tungsten and vanadium; Use a 25°F to

50°F safety factor; 300 SS overlay and/or roll bond clad material

UT using combination of velocity ratio and backscatter (AUBT); In-situ metallography; VT for blistering;

WFMT and RT in advanced stages with cracking

No titanium in known hydriding services such as amine or sour water; Use all

titanium if galvanic coupling may promote hydriding


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Appearance

N/A

N/A

N/A

N/A

N/A

Cracking particularly at welds or areas of high restraint

Cracks typically straight, non-branching, with no plastic

deformation; Limited intergranular cracking


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Appearance

"fishmouth"

Noticeable deformation may be observed; May have significant

bulging before final fracture occurs

Cracks propagate transverse to the stress and usually dagger-shaped, transgranular, and oxide filled; May

stop and restart; May be axial or circumferential, or both,at the same location;

Open burst with edges drawn to a near knife-edge

Cracks at the toe of weld in the HAZ of the ferritic material

Surface initiating cracks may appear as “craze” cracks

Localized loss in thickness; Pits, grooves, gullies, waves, rounded holes and valleys; Often with a

directional pattern

Sharp-edged pitting but may have a gouged appearance in rotational

components

“clam shell” type fingerprint with concentric rings called “beach

marks”

Crack initiating at a point of high stress or discontinuity

Cracking, spalling or lift-off from the substrate, softening or general degradation from exposure to

moisture; Erosive services: washed away or thinned

Intergranular and can be surface breaking or embedded

More active material can suffer generalized loss in thickness or

crevice, groove or pitting corrosion

General or localized; Normally a distinctive iron oxide (red rust)

scale forms

May be highly localized; Loose, flaky scale covering the corroded

component


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Appearance

N/A

General corrosion, localized underdeposit, pitting, MIC, SCC,

fouling, grooving along ERW tubes

Oxygen: pitting anywhere in the system; CO2: smooth grooving

Localized thinning and/or pitting; May be deep pitting and grooving in

areas of turbulence

General wastage often with broad, shallow pits

Localized pitting under deposits or tubercles; Cup-shaped pits within

pits

External thinning with localized losses due to pitting

Localized metal loss as grooves in a boiler tube or thinned areas under

insulating deposits;

Often a color change or deep etched appearance; May be

uniform through the cross-section or localized

Widespread or localized; Damaged areas will be soft and easily gouged

with a hand tool

General thinning; Usually covered on the outside surface with an

oxide scale

Most often uniform thinning but may be localized; Sulfide scale will

usually cover the surface

In advanced stage may be a volumetric increase

Low alloys can be uniform but usually small pits filled with crumbly residue; SS and high alloys local,

deep, round pits


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Appearance

“alligatorhide”

Possible fouling or corrosion

"needle-like" particles of iron nitrides

"spider web"; Branched, transgranular, and may have "crazecracked" appearance

"rabbit ears"; Transgranular but not branched, often multiple parallel

cracks

"spider web"; Predominantly intergranular, parallel to weld in

adjacent base metal but can occur in the weld or HAZ

Cu: bluish corrosion products at surface cracks, single or highly

branched, either trans or intergranular

Brittle cracks in an otherwise ductile material

Can initiate sub-surface, but in most cases is surface breaking;

Higher strength steels cracking is often intergranular

General uniform thinning, localized corrosion or localized underdeposit

attack

General loss in thickness with potential for high localized rates;

Low velocities may have localized under-deposit corrosion


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Appearance

General or localized thinning of CS

General uniform thinning, localized corrosion or underdeposit attack

Uniform loss in thickness from the process side with an iron sulfide

scale

Localized general or severe thinning of CS; May be

accompanied by cracking due to hydrogen stress cracking, blistering

and/or HIC/SOHIC damage

Localized corrosion, pitting, or flow induced grooving in high velocity

areas

General or localized corrosion of CS

General thinning; Localized corrosion or underdeposit attack

can occur

General but attacks CS HAZ rapidly; Hydrogen grooving in low

flow

Intergranular; Quite localized; Typically next to welds, but may be

in base metal

Surface cracking on ID primarily in HAZ, but also in weld or adjacent to HAZ; Typically parallel to weld, but

in weld, either transverse or longitudinal

Blistering, HIC "stepwise cracking", SOHIC stacked arrays, SSC through thickness potentially

Surface breaking intergranular cracks

"spider web"; Parallel to weld in adjacent base, but also in weld or HAZ; Predominantly intergranular


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Appearance

N/A

Intergranular and adjacent to iron carbide areas in CS; Some

blistering may be visible to the naked eye

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API-RP-571-Damag-10