corrosion tests and standards

부식테스트의목적과그방법부식테스트의목적과그방법Corrosion Tests and Standards

INTRODUCTION Corrosion Fundamentals Forms of Corrosion

CORROSION TEST & STANDARDU if C i Uniform Corrosion

Salt Spray TestPitting/Cre ice Corrosion Pitting/Crevice Corrosion

Intergranular Corrosion Stress Corrosion Cracking Stress Corrosion Cracking Sour Corrosion MiscellouneousMiscellouneous

2

재료가주변환경과의 (전기)화학반응에의해서원래의특성을잃고열화되는현상

Metallurgy in Reverse (Natural process!)

4Cited from Fontana, M.G., Corrosion Engineering. 3rd ed. 1986, New York: McGraw-Hill.

The leak caused by corrosion at this elbow started the fire that destroyed this refinery

Alloying to resist corrosion (SS, cupronickel, etc.) Metallic coatings (galvanizing)g (g g) Organic coatings (paint, lining) Electrochemical protectionp Cathodic protection Anodic protectionp

Corrosion inhibitors Automotive cooling systems, cooling towers, boilers, etc.g y , g , ,

11

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4Uhlig, H.H. and R.W. Revie, Corrosion and Corrosion Control. 3rd ed. 1985, New York: John Wiley & Sons.

CC Technologies study – March 2002 In 2000 about 3.1% of GDP spent on corrosion repair and p p

control Total cost $276Billion! Of industries analyzed, the cost was $137.9 Billion

Country Direct Cost Indirect Cost USA 303.76 200 (approximately)

Japan 59.02

Former USSR 55.01

Germany 49 26Germany 49.26

UK 8.51

Australia 7.32

Belgium 6.75

India 3.78

Poland 3.53

Canada 3.38

.....

.....

.....

Global 510.14 940 (approximately)

145Bhaskaran, R., N. Palaniswamy, and N.S. Rengaswamy, Global Cost of Corrosion—A Historical Review, in Corrosion: Materials, Vol 13B, ASM Handbook. 2005, ASM International.

An 8" in. dia oil pipeline 225 miles long with 1 inch wall thickness was installed with no corrosion protection systemWith i t t ti l th di t ti it With appropriate protection namely cathodic protection, it would have a thin wall thickness which would

S 3 700 t f t l ( th th illi d ll ) Save 3,700 tons of steel (worth more than one million dollar) increase internal capacity of the pipeline by about 5%.

183Corrosion Doctors Website. Homepage: http://www.corrosion-doctors.org

Ensuring maximum life of new equipment Preservation of existing equipment Protecting or improving the quality of a product in order to maintain or improve g g y

a competitive position. Avoiding costly interruptions of production. Reducing or eliminating losses of valuable products by spillage or leaks. Refitting of equipment withdrawn from service because of corrosion Refitting of equipment withdrawn from service because of corrosion. Reducing hazards to life and property that might be associated with corrosion: Explosions of pressure vessels or piping systems

release of poisonous or explosive gases or vapors release of poisonous or explosive gases or vapors

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재료선정/방식법의적정성에대한확신이없을때, 또는결과를예측하기어려울때

목적 Accelerated tests to demonstrate products durability

A t t t t h th t t i l t t d d Acceptance tests to show that a material meets standard Monitoring tests to show changes in a system corrosivity Research tests to determine mechanism of corrosion

실험실평가 Service life 예측 Service life 예측 주어진환경에서재료의사용적합성평가 새로운재료의 ranking목적

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ASTM G48 Pitting and Crevice Corrosion Resistance Ferric chloride (FeCl3), 6% solution( 3), 72H at 22oC (room temperature) Report pitting or crevice corrosionp p g Simulates sea water attack of stainless steels

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ASTM G69, Test of metallurgical condition of Al alloys Measure corrosion potential, E, in salt solution

C i E Z d E Cu increases E, Zn reduces E Heat treatment determines condition Condition affects strength and corrosion tendencies Condition affects strength and corrosion tendencies Solution: 1M NaCl + 2.7%H2O2, 22oC Surface preparation: steel wool rubp p 1 Hour immersion Measure potential every 5 minutes after 30 minutes against SCE

reference electrodereference electrode Average result: -750±10 mV for pure Al Al foil is pure AlAl foil is pure Al

25

ASTM C876 Corrosion of steel rebar in concrete Potential indicates when corrosion of steel is occurringg Copper/copper sulfate reference cell Chloride causes steel to corrode Deicing salt usually reason for problem Sea water also causes problemsSea water also causes problems

Potential > -0.20 V, rebar is not corrodingPotential 0.20 V, rebar is not corroding Potential <-0.35V, rebar is corroding Potential in between then the rebar may be corroding Potential in between then the rebar may be corroding

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Potential > -0.20 V, rebar is not corroding Potential <-0.35V, rebar is corroding g Potential in between then the rebar may be corroding

보통부식시험의변수가많다. 부식시험결과의재현성이떨어져서신뢰성이의심되는경우가많다.

표준화로재현성을높일수있음 ASTM, NACE, etc.

32

Document that provides specific procedures or set of requirements for a commercial product or process that q p pattains a consensus of knowledgeable people.

Compliance with standards is voluntary unless mandated p yby law.

International Society of Testing Materials – 1880’s ASTM founded ~1898 NACE founded ~1948 ISO ~1960

34

ASTM (1904): Steel vs. Wrought iron in atmosphere ASTM (1937): Salt spray test, B117

NACE th di t ti i NACE: cathodic protection issues

ASTM reorganization (1964) ASTM reorganization (1964) Created Committee G-1 on Corrosion on Metals Volume 03 02 Volume 03.02

NACE (~1960s) Created Technical Practice CommitteeCreated Technical Practice Committee

ISO (1978) Created TC 156 on Corrosion on Metals (11 Working Groups)( g p )

35

Corrosion is electrochemical Potentiostats became available (1960s)( ) Passive-active behavior of stainless steel revealed with

potentiostat.p Issues with reliability and reproducibility.

36

430SS in 1.0N (0.5M) H2SO4 aqueous solution. Single lot of SSg Carefully designed procedure 10mV/m from Ecorr.corr

37

39

FIG.5- Potentiodynamic Polarization Plot for UNS S43000 Stainless Steel in 1 N Sulfuric Acid at 30º C Showing Range of Data from Interlaboratory Program from ASTM G 5

40

FIG. 6- Potentiostatic Polarization Plot of UNS S43000 Stainless Steel in 1 N Sulfuric Acid at

30º C Showing Acceptable Data Range and Crevice Corrosion Affected Data Points from ASTM G 5

First reference method Results demonstrated reproducibilityp y Method widely used to qualify laboratories Basis of many potentiodynamic studiesy p y Method upgraded and improved several times

41

Test method (TM) ASTM G5

Standard practice (SP) aka RPp ( )

Specificationp ASTM G188

42

• Industries dealing with corrosive situations• Engineers and designers g g• Governments specifying materials for projects• Academics teaching how to use materials in the real worldg

43

Uniform Corrosion Pitting/Crevice Corrosiong Intergranular Corrosion Stress Corrosion Crackingg Sour Corrosion Hydrogen Induced Crackingy g g Sulfide Stress Corrosion

Miscellouneous Hydrogen Induced Disbonding (HID) Salt Spray Test, etc.p y ,

45

가장일반적 금속표면에걸쳐서부식환경이균일함 금속은금속학적/조성적으로균일

금속손실측면에서는가장중요한부식형태 금속손실측면에서는가장중요한부식형태 쉽게육안관찰가능하고부식방지가능(alloying)

Atmospheric corrosion (rusting) Corrosion in acid solutions

무게감량시험 (침지시험) ASTM G31

▪ Standard Practice for Laboratory Immersion Corrosion Testing of Metals NACE TM0169

경험적인시험시간▪ 2000/(expected corrosion rate in mpy) 시간

관련표준 관련표준 G1 Standard Practice for Preparing, Cleaning, and

Evaluating Corrosion Test Specimens1Procedure Evaluating Corrosion Test Specimens1Procedure

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특징 실시간순간(instantaneous) 부식속도제공실시간순간( ) 부식속 제공 Coupon의 Time-corrosion rate data 제공 빠른측정법빠른측정법 전용장비와지식/기술필요

ASTM 표준들준들 G59 Standard Test Method for Conducting Potentiodynamic

Polarization Resistance Measurements (LPR)( ) G96 Standard Guide for On-Line Monitoring of Corrosion in

Plant Equipment (Electrical and Electrochemical Methods)

50

Rp = E/iapp = B/icorr

51

금속의내식성과금속표면에형성된유기/무기코팅층의내식성을평가하기위한가장오래된가속시험법

주로해양환경의모사가속시험 보통같은시험장비로여러표준시험이가능함 Humidity Testingy g

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시험온도 Fog density (condensation-collection rate)g y ( ) 용액 pH 비중 Static 시험기간동안 salt의종류및시험조건이동일시 기 동 의종류 시 이동 시험온도,

Cyclic

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ASTM B117, B368, G85 각단체, 제조사별로 ASTM에근간한별도 spec. 보p유 GM 4298/Salt Fogg Mil Standard 810E, method 509.3

DIN 50018, ISO 9227, Slat fog, acetic-acid, copper accelerated salt spray (CASS)

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Static 시험기간동안 salt의종류및시험조건이동일 보통, 24h/day, 7 dyas/week ASTM B117

Cyclic미리지정된노출시간 노출조건의반복 미리지정된노출시간, 노출조건의반복

변수: 온도, RH, 부식성물질, 시간등 SAE J 2334 DIN 50018/SO2 GM 9540P Ford APGE Honda SAE J-2334, DIN 50018/SO2, GM 9540P, Ford APGE, Honda

HES D6501 Sec. 3.18/3.37, CCT I, II, III, IV (Nissan), BMW CCT, etc.

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Designation Title

B 117 Test Method of Salt Spray (Fog) Testing

B 368 Method for Copper-Accelerated Acetic Acid Salt Spray (Fog) Testing (CASS Test)

B 735 Test Method for Porosity in Gold Coatings on Metal Substrates by Nitric Acid Vapor

B 799 Test Method for Porosity in Palladium Coatings by Sulfurous Acid/Sulfur Dioxide Vapor

D 2803 Guide for Testing Filiform Corrosion Resistance of Organic Coatings on MetalD 2803 Guide for Testing Filiform Corrosion Resistance of Organic Coatings on Metal

D 2933 Test Method for Corrosion Resistance of Coated Steel Specimens (Cyclic Method)

G 60 M th d f C d i C li H idit T tG 60 Method for Conducing Cyclic Humidity Tests

G 85 Practice for Modified Salt Spray (Fog) Testing

G 87 Practice for Conducting Moist SO2 Tests

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주로유기/무기코팅/도금층의특성평가 유사규격 DIN 50021-SS GM 4298

ISO 9227 ISO 9227 목적

표준화된부식성환경에서의내석성비교시험 표준화된부식성환경에서의내석성비교시험(comparative testing or ranking)▪ Quality audit functionQuality audit function▪ “passing” or “failing”

실제 outdoor환경에노출된재료성능을대변하지않음.

62

일정온도로유지되는챔버내에일정농도의 NaCl수용액을atomizing시켜서부식성의 fog atmosphere유지 5% NaCl

▪ NaCl수용액을만들기위한 reagent water에대한규정 (D1193)▪ NaCl용액의불순물함량등규정

pH: 6.5~7.235 1 1 1 7oC 35+1.1 or -1.7oC

Fog의응축속도: 1~2 ml/collector 24 to 5000hrs.

24시간단위로시험시간변화▪ 24시간단위로시험시간변화▪ # of cycles는 buyer와 seller의상호합의

Orient: 12시방향으로부터 15-30o angle (if not specified)▪ 자동차부품 경우에따라서는 “in-car” 위치자동차부품, 경우에따라서는 in car 위치▪ Free-falling mist가가능하도록시편배치가중요

시편회전및일일체크시를제외하고는시험기간동안챔버는닫힌상태로유지한다.

Hot-dip galvanized steel시험등

63

ISO salt spray test spec. (ISO 9227) 최소 0.2 m3 이상의캐비닛내부볼륨, 0.4m3 추천,

Large Chamber (walk-in type & drive-in type)

64

일반적인형태부피: 0.25 ~ 4.5 m3 이상

(overcrowding)

Salt fog cycle Dry cycle Controlled humidity cycle

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Solution spray cycleImmersion clycle

1987년추가 부식으로인한무게감량측정을위한시편설치 SAE 1008 CS (76 x 127 x 0.8 mm) 48, 96, 168h의시험후무게측정, , 의시험후무게측정 이후무게측정주기는 user가정함

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비교시험 (comparative testing or ranking) Quality audit functiony “passing” or “failing”

70

ASTM G85 (acetic acid salt spray (fog) test) 유기/무기코팅재에적용가능 특히, Ni-Cr, Cu-Ni-Cr, Cd도금층의평가특히, Ni Cr, Cu Ni Cr, Cd도금층의평가 제품품질의 consistency 평가 5% NaCl + acetic acid로 pH산성화 (3.1-3.3) 35+1 1 or -1 7oC 35+1.1 or -1.7 C 16h 또는 144 to 240h

ASTM B368 (CASS test) 장식도금 (Ni Cr Cu Ni Cr Cd도금)의평가 장식도금 (Ni-Cr, Cu-Ni-Cr, Cd도금)의평가 Anodized, chromated, phoaphated Al평가 Automotive company

5% N Cl 1 C Cl 2H O (3 8L) ti id ( H 3 1 3 3) 5% NaCl + 1g CuCl22H2O (3.8L) + acetic acid (pH 3.1-3.3) 49+1.1 or -1.7oC 6 to 720h

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ASTM G1 Standard Practice for Preparing, Cleaning and Evaluating Corrosion Test Specimens

ASTM G46 Guide for Examination and Evaluation of Pitting ASTM G46 Guide for Examination and Evaluation of Pitting Corrosion

ASTM D609 Practice for Preparation of Cold-Rolled Steel P l f T ti P i t V i h C iPanels for Testing Paint, Varnish, ConversionCoatings and Related Coating Products

ASTM D1654 Standard Test Method for Evaluation of Painted ASTM D1654 Standard Test Method for Evaluation of Painted or Coated Specimens Subjected to Corrosive Environments

ASTM D610 Standard Practice for Evaluating Degree of ASTM D610 Standard Practice for Evaluating Degree of Rusting on Painted Steel Surfaces

ASTM D714 Standard Test Method for Evaluating Degree of g gBlistering of Paints

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시험조건 시험번호

시편및시험결과 재료/코팅재설명시험번

사용된염(salt)과물의종류 시험온도

재 팅재설명 시편의종류 시편크기

응축수의부피 (ml/80cm2

collector) % NaCl in water

전처리및 cleaning방법 (e.g., ASTM D609)

챔버내의시편거치방법% NaCl in water 응축수의 pH

챔버내의시편거치방법 시편 edge보호방법 시험기간 시험시작/종료시간 시험중단원인및시간검사결과 검사결과

시험사진/그래프73

D714

D610

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.0003/8um Zinc Nickel Black PS8955.0003/8um Tin Zinc Clear GMW3200

.0003/8um Zinc Cobalt Black PS8955

.0002/5um Zinc Nickel Clear PS8955

.0003/8um Zinc Nickel Clear PS8955.0003/8um Zinc Cobalt Black, Topcoat PS8955

.0002/5um Zinc Cobalt Clear PS8955

.0003/8um Zinc Cobalt Clear PS8955.0003/8um Zinc Iron Black, Topcoat PS8955

.0002/5um Zinc Iron Clear PS8955

.0003/8um Zinc Nickel Clear, Topcoat PS8955.0002/5um Zinc Cobalt Clear, Topcoat PS8955

.0003/8um Zinc Cobalt Clear, Tocoat PS8955.0003/8um Zinc Iron Black PS8955

.0002/5um Zinc Iron Clear, Topcoat PS8955

.0003/8um Zinc Iron Clear, Topcoat PS8955.0003/8um Zinc Nickel Black, Topcoat PS8955

0003/8um Zinc Clear GMW3044-N.0003/8um Zinc Clear, Clearcoat, Wax FordS437

.0003/8um Zinc Clear, Clearcoat, Wax GMW3044-G.0003/8um Zinc Yellow

.0005/12um Zinc Yellow.0003/8um Zinc Iron Clear PS8955

.0002/5um Zinc Nickel Clear, Topcoat PS8955, p

0003/8um Tin Zinc Clear PS8956.0004/10um Tin Zinc Clear PS8956.0005/12um Tin Zinc Clear PS8956

.0002/6um Tin Zinc Clear PS8956.0003/8um Zinc Black

.0005/12um Zinc Black.0005/12um Zinc Clear

.0003/8um Zinc Clear GMW3044 N

.0005/12um Zinc Clear, Clearcoat.0003/8um Zinc Clear Clearcoat GMW3044-X

.0005/12um Zinc Clear Clearcoat Wax.0003/8um Zinc Clear JS500.0003/8um Zinc Clear JS600

.0003/8um Zinc Clear, Organic Topcoat S440.0003/8um Tin Zinc Clear PS8956

0 50 100 150 200 250

Hours to White CorrosionZinc Alloy Finishes

RB211-524 G/H Stage 3 HPC Vanes (Rolls-Royce EAK alloy) 1 hr. 5% salt fog (ASTM B117-73)

2 h t 450ºC (842ºF) 2 hrs. at 450ºC (842ºF) 1/2 hr. cool 20 hrs in 100% relative humidity (ASTM D2247) 20 hrs. in 100% relative humidity (ASTM D2247)

5 cycles

CallaCor-BanCorrosion Inhibiting Calla

Aircraft Appearance Products

Corrosion Inhibiting CompoundsSur-Prep

Critical Surface Cleaners & Treatments

Aero-LubeLubricants & Lubricating Lubricants & Lubricating Compounds

국부부식의한형태 SS의경우해수와같이 halides (Cl-) 이온을함유한중성/산성용액에서발생을함유한중성/산성용액에서발생

부동태층의약화된부위에서종종발생 (예: slag inclusion or surface defects.)

Pitting corrosion through the tube wall

83

Pitting corrosion of SS condenser tube

Specimens of various stainless steels after G 48 testing at 80°C for 24 hours.

“Standard Test Methods for Pitting and Crevice Corrosion Resistance of Stainless Steels and Related Alloys by Use of Ferric Chl id S l ti A F i hl id itti t t”Chloride Solution, A: Ferric chloride pitting test” Shell ES/247 Revision 2, 2003

SS의공식발생에대한저항성비교목적 SS의공식발생에대한저항성비교목적 6% FeCl3 용액에시편침지 (강산화성, 강산성) 22±2 or 50±2°C 72 hrs 가속시험육안관찰 게감량 육안관찰/무게감량

84Specimens of various stainless steels after G 48 testing at 80°C for 24 hours.

Pit의형태, 크기, density 육안검사

(a) Narrow & dip (b) Elliptical( ) Wid d h ll (d) S b f

85

(c) Wide and shallow (d) Subsurface(e) Undercutting (f) Shapes determined by microstructural orientation


Ferric chloride 용액은 Cl-를함유한용액중에서철강재료의공식이발생할때 pit 또는 crevice내에존재p하는용액과유사한조성을가짐. 강한산화력으로 SS의전위를 pitting potential이상으로유강한 화력 의 위를 p g p 이상 유지시키는효과

강산성은재부동태화를억제하는효과 시험결과는다음환경에서합금의상대적인내식성평가에적용가능 상온의실제해수 강산화성, 산성의 chloride함유환경

87

전기화학적으로일정주사속도로전위를상승시키면서 부동태 피막의 파괴로 전류밀도가 급격하게증가하는전위 (E )를구함하게증가하는전위 (Epit)를구함 Critical pitting potential (CPP)이라고도부름

반대방향으로 전위를 scan하면 repassivationpotential(Erp)을구할수있음 Epit Pitting이일어나지않는다면 Epit=Erp Pitting이일어난다면 hysteresis loop를관찰할수있음. Erp

a. E>Epit : Pits nucleation occurs.b. Erp<E<Epit : New pits can not be formed, but

the existing pits may propagate E

the existing pits may propagatec. E<Erp : the metal remains passive (or pits repassivate)

log i

log i

ASTM G61: Standard Test Method for Conducting Cyclic Potentiodynamic Polarization Measurements for Localized Corrosion Susceptibility of Iron-, Nickel-, or Cobalt-Based Alloys

90

Epit = A log [Cl-] + B

SS의 Cr, Mo, N content 이국부부식에대한저항성을결정하는인자

PRE %Cr + 3.3 (%Mo + 0.5%W) + 16~30 %N ( )

91

Critical pitting temperature Pitting corrosion이발생하기시작하는임계온도 CPT가낮을수록 pitting corrosion에대한저항성이낮음 CPC (oC) = 2.5 %Cr + 7.6 %Mo + 31.9 %N – 41.0

0 85oC 사이에서 72h(C 24h/E) 시험 (약 5C씩온도증가시키며) 0~85oC 사이에서 72h(C, 24h/E) 시험 (약 5C씩온도증가시키며)

93

정전위법에의해서전류가급격히증가하는온도를구함 1M NaCl용액 700mVSCE

1C/min 전류밀도가 100 μA/cm2 이상 60초이상유지되는온도전류밀 가 μ 이상 이상유지되는온

1. Cooling coil2. Gas distributor3 R f l t d3. Reference electrode4. Test specimen5. Counter electrode6 Temperature sensor6. Temperature sensor7. Immersion heater8. Specimen holder with connection9 Reflux cooler

94

9. Reflux cooler

정전위법에의해서전류가급격히증가하는온도를구함 1M NaCl용액 700mVSCE700mVSCE

1C/min 전류밀도가 100 μA/cm2 이상 60초이상유지되는온도

1. Cooling coil2. Gas distributor3 R f l t d3. Reference electrode4. Test specimen5. Counter electrode6 Temperature sensor6. Temperature sensor7. Immersion heater8. Specimen holder with connection9 Reflux cooler

95

9. Reflux cooler

Epit

Erp

E

log i

97

99Simulating natural seawater

Supplementary technical requirements for the supply of components in 6% Mo Austenitic, 22% Cr Duplex and 25% Cr Super Duplex Stainless Steel

Requires Impact testing Hardness testing Microstructure examination and ferrite phase balance (not 6Mo) Pitting corrosion testing (additionally, stress corrosion cracking for 25Cr if specified)

Base Metal: ▪ ASTM G48 method A test required for each lot. Test temperature shall be 122°F (50°C) and the

exposure time 24 hours Corrosion test specimens shall be at same location as those for tension exposure time 24 hours. Corrosion test specimens shall be at same location as those for tension tests. The test shall expose the external and internal surfaces in the as delivered condition (including pickling) and a cross section surface in full wall thickness.

Weld▪ Corrosion test shall be performed on one sample from each of the 3 and 6 o’clock welding ▪ Corrosion test shall be performed on one sample from each of the 3 and 6 o clock welding

locations in accordance with ASTM G48 method A. A sample including the root shall be taken and be exposed to the solution. Test temperature shall be 104°F (40°C) and exposure time 24 hours.

No pitting at 20X magnification & weight loss shall be less than 4 0 g/m2 No pitting at 20X magnification & weight loss shall be less than 4.0 g/m2.

101Procurement Spec. for MWP

원리적으로 pitting corrosion가같으나, 인위적인틈새나균열내부에서발생 Between flange joints, Under deposits on the metal surfacep In welds with incomplete penetration

Pitting보다낮은온도, 낮은 Cl-농도에서발생g 다낮은온 ,낮은 농 에서발생 낮은유속에서발생 역시 PRE가중요한제어인사역시 가중 한제어인사

103

Crevice corrosion of Ti flange in hot seawater Crevice corrosion of SS

Crevice corrosion of socket weld at gap formed between type 304L pipeAnd type 316L valve

Pitting corrosion과같은시험 (6% Ferric chloride) 인위적으로 crevice를형성시킨후시험 인위적으로 crevice를형성시킨후시험

문제점 Rubber bend로부터의압축응력이균일하지않음

고무줄이끊어지면무효무줄이끊어지면무 Crevice area/exposed area의비율이명확하지않음

부식이종종 PTFE실린더하부Rubber bend

부식이종종 PTFE실린더하부가아니라고무줄하부에서발생

106

ASTM G78: Standard Guide for Crevice Corrosion Testing of Iron-Base and Nickel-Base Stainless Alloys in Seawater and Other Chloride-Containing Aqueous Environments

[0.5M FeCl3 + 0.05M NaCl] 용액중에최소 30일침지

ASTM G48D/F MCA를이용하되원리는 CPT측정과같음.를이용하되원리는 측정과같음

전기화학적방법전기화학적방법

110


111

출 부식환경에노출된재료가결정립(grain)에서는부식이미미하나, 결정립계(grain boundary) 또는입계바로인근에서선택적으로부식이발생하는현상

스테인리스강의예민화 2xxx Al합금에서 ClAl2의입계석출로입계인근 Cu-depleted zone의선택부식 114

의예민화SS의예민화(sensitization) 또는weld decay

결정립계에 C bid 가석출하게결정립계에 Cr carbide가석출하게되면 SS는예민화되었다고말한다.

예민화는용접중의열영향부(HAZ)에서주로발생하고그결과로나타나는부식을 weld decay라고함.

SS가약 650C 이상으로유지되면Cr carbide가형성됨.

Production Fabrication Welding

Heat treatment Heat treatment

116Fe-Cr alloy in boiling 50% H2SO4 with Fe2(SO4)3

IGC에대한 susceptibility 시험 1926년 CuSO4-H2SO4 산세용액에서 ASS의 IGC가발견된년 4 2 4 산세용액에서 의 가발견된후시험법개발 (모사시험)

주의: 균일부식/국부부식에대한저항성평가시험아님일반적으로산성, 산화성분위기시험 (pH, 온도, 전위등은시험방법에따라다름)

가속시험법 가속시험법 ASTM A262: 6 practices

117

PRACTICE TEST TEMP. TIME APPLICABILITY EVALUATION

A Oxalic acid etchScreening test Ambient 1.5 m Chromium carbide sensitization

Only (1.5A/cm2)Microscopic: classification of etch Structure (screening test)

BStreicher

Fe2(SO4)350% H2SO4

Boiling 120 h Chromium carbide Weight loss corrosion rate

CHuey 65% HNO3 Boiling 240 h Chromium carbide and σ phase Weight loss corrosion rate

DM d St ß

10% HNO33% HF 70°C 4 h Chronium carbide in 316, 316 L,

317 d 317 LCorrosion ratio compared to solution

l d iMod. Strauß 3% HF 317 and 317 L annealed specimen

E 6% CuSO410% H SO Boiling 24 h Chromium carbide Examination for fissures after bendingStrauß 10% H2SO4Metallic copper

Boiling 24 h Chromium carbide Examination for fissures after bending

CuSOF

CuSO450% H2SO4Metallic copper

Boiling 120 h Chromium carbide in cast 316 and 316 L Weight loss corrosion rate

118

목적 1927~1930년개발 (Du Pont) 질산제조공장에서기존 12% Cr 강대신 18% Cr함유강의적용이증가하면서기존시험용액(CuSO4-H2SO4)을대체할가속시험법의필요성대두할가속시험법의필요성대두

시험조건시험조건 Boiled 65% HNO3 solution Fesh solution을이용하여 5회의 48h periods.을이용하여 회의 p 무게감량에근거한부식속도측정 (각 period별) Cr탄화물석출및 σ상석출효과검증

119

질산용액에서시험이이루어지므로 Cr함량이클수록부식속도가낮다. 화학조성으로부터 baseline corrosion rate를구할수있음. 이기준값으로부터예민화도및 annealing 정도등에따이기준값 부터예민화 및 g 정 등에따른부식속도변화와같은정보를얻을수있음.

예민화정도와 σ상석출효과구분못하지만Fitness-for-purpose 시험의효과있음

120

1930년개발 (Strauß) 유럽에서많이사용유럽에서많이사용

Huey test (질산)보다 mild함 Cu의첨가로부식이가속화되어시험시간단축의 가 부식이가속화되어시 시 축

시편균열(crack/fissure) 검사에의한정성적평가법시 ( ) 사에의 적평가

122

Corrosion Potential 0.30~0.58VSHE

부식속 부식속도 입내 ~10-1 μA/cm2

입계 ~10 μ A/cm2

예민화가심한경우최대 105배정도의부식속도차이

부식은매우급속하게 1 μm정도두께의 Cr고갈영역에국한되어두께의 Cr고갈영역에국한되어발생함

무게감량이매우적고, 입계의부식관찰이어려움부식 이어려

따라서, 시편을 bending시킨후실험을진행한후균열을관찰하여평가함하여평가함

123

예민화온도에서시편을열처리한후시험 Equivalent 표준 DIN 50914 ASTM A262 practice E

ISO 3651/2 ISO 3651/2 시편은검사전에 bending

IGC로부터유래된균열에대한육안검사 만일균열의유래가의심스러우면 metallographic 만일균열의유래가의심스러우면 metallographic

examination을통해입계부식여부확인 Cr-carbide 석출검출, Sigma상석출은검출불가

124

125

Photograph showing a side view of an ASTM A262 method E (Strauss) specimen after exposure and bending.

새로운 CRA의지속적인개발 -평가시험필수 그러나, 초기 65% nitric acid 시험시간이너무김 실제시험시간: 240h 실제시험시간: 240h 용액준비: 48h 시편전처리 + 선적 + 결과분석미세 직을 석하 의필 성대 미세조직을분석하는 screening test의필요성대두 Oxalic acid etch test 10% oxalic acid, 1.5분, 1.0A/cm210% oxalic acid, 1.5분, 1.0A/cm 결과분석을위한 “over-etching”

결과해석 (by Streicher)St t t Step structure

Ditch structure Dual structure

126

Step or Dual structure: “passing”

Ditch structure가얻어지는경우에는Huey test(Practice C)에의한검증필수

127Step structure Ditch structure Dual structure

128

Image Optical micrographs obtained in ASTM A262 Practice A test for 316

1958년개발 목적 시험시간 240h(65% Nitric acid)를 120h로줄임 시험시간 240h(65% Nitric acid)를 120h로줄임 Cr carbide에의한 IGC만을변별할목적 Huey test와달리 Mo함량변화에 insensitive방법 방법 시편을끓는 [ferric sulfate+sulfuric acid] 용액에최대 5일간침지 무게감량에의한부식속도측정무게감량에의한부식속도측정

효과 예민화정도를검출서로다른합금사이의 IGC resistance를비교할수없음 서로다른합금사이의 IGC resistance를비교할수없음

Plant service problem으로부터파생된표준이아니므로 fitness-for-service 목적으로는사용하지않음.

G28A와같은시험방법

129

CORROSION AUSTENITIC STEELS FERRITIC STEELSSOLUTION

CORROSION POTENTIAL

(ESHE)

AUSTENITIC STEELS FERRITIC STEELS

Cr-carbide SigmaCarbides and Nitrides Intermetallics

Fe-Cr-Mo(Ti)Fe-Cr Fe-Cr-Mo

316 316L 317 65% HNO3 1-1.25 yes 316, 316L, 317, 317L, 321 yes yes yes

F (SO ) N (321 ibl yes

Fe2(SO4)3 +H2SO4

0.85 yes No (321 possible exception) yes yes (not σ or χ in

unstabilised Fe-Cr-Mo alloys)

C SO +CuSO4 +H2SO4

0.6 yes no yes yes no

As above but with metallic Cu 0.35 yes no yes yes nometallic Cu y y y

10% HNO3 +3% HF 0.15-0.55 yes no yes yes no

5% H2SO4 -0.35 yes no noyes

(not σ or χ in unstabilized grades)

no

Exposure Time Criteria for passingUNS No. Alloy Name Sensitizing Standards Exposure Time, h

Criteria for passingMax. mm/month

S30400 Type 304 None Oxalic acid (A262A) 120 (a)

Ferric sulfate (A262B) - 0.1

S30403 Type 304L 1h at 675C A262A - (a)

Nitric acid (A262C) 240 0.05

S30908 Type 309S None A262C 240 0.025

S31600 Type 316 None A262A - (a)

A262B 120 0.1

S31603 Type 316L 1h at 675C A262A - (a)

A262B 120 0.1

S31700 Type 317 None A262A - (a)

A262B 120 0.1

S31703 Type 317L 1h at 675C A262A - (a)

A262B 120 0.1

S32100 Type 321 1h at 675C A262C 240 0.05

S34700 T 347 1h t 675C A262C 240 0 05S34700 Type 347 1h at 675C A262C 240 0.05

N08835 Incoloy 825 1h at 675C A262C 240 0.075

N06690 Incoloy 690 1h at 540C A262C 240 0.025 133

특징 전기화학적시험방법 (1978년개발)전기화학적시험방법 ( 년개발) 원자력발전소 boiling water(289oC, 0.2-8 ppm O2)용 304SS배관의 SCC사례발생후비파괴적검사방법의필요성대두

예민화도(degree of sensitization; DOS)를비파괴적, 정량적으로검출

탈기된 [황산+KSCN(deactivator)]용액중에서시편을전기화학적으로분극시킴

134

시험방법 탈기된 [황산+KSCN(deactivator)]용액중에서시편을전기탈기된 [황산 ( )]용액중에서시편을전기화학적으로분극시킴

전위를 Ecorr으로유지시킨후, 부동태영역으로전위를상승시키고, 이후 cathodic 방향으로분극시킴

예민화된입계가결정립보다활성화되어전류(전하량)가더많이흐 게되는원리를이용가더많이흐르게되는원리를이용▪ 이전류(전하량)의크기가 DOS에비례

가정 부식은모든입계에서균일하게일어남 가정: 부식은모든입계에서균일하게일어남.

Pitting 에의한오차발생가능 Pitting 에의한오차발생가능

135

Single loop (SL) EPR testg ( )

P : Degree of Sensitization

Q

Pa: Degree of SensitizationQ: Charge passed during testGBA: Grain boundary area =As[5.09544 ×10-3exp(0.34696X)As: specimen surface areaX: ASTM micrograin size number (ASTM E112)

136GBA

QPa

탄화물석출시작

0.4<Pa<2.0Step/dual 중첩(microstructure관찰 추천)

1. 0.01<Pa<5.0Ferric sulfate시험의부식속도변화거의없음EPR시험으로예민화도검출효과적

2. 5<Pa<20Pa증가에따라부식속도증가

3. Pa>20EPR시험은거의포화, 화학적방법이더신뢰도가높음

137

SL-EPR시험의문제해결을위한시 +300mV

험법 (1980) Pitting of non-grain g g

boundary Surface-finish effect

-230mV

▪ 140μm finish▪ SL-EPR은 1μm

예민화도

Scan rate: 6V/h~ -400mV

예민화도 Ir : Ia

138

IGC 시험결과를 TTC의형태로표현하는경우가많음. (according to ASTM G28, Streicher, ferric sulfate+sulfuric acid)

141

142Cited from http://www.dandvik.com

Sensitization occurs in the range 550-850°C, e.g. during heat treatment or welding (HAZ). g ( )

Cr-carbide formation (or other types of precipitates) can lead to Cr depletion and selective attack of a zone next to pthe grain boundaries or in the weld fusion line.

Materials with good IGC resistanceg ELC steels and Ti/Nb(Cb)-stabilized steels.

IGC testing mainly according to Strauss or Huey.g y g y

143

Mechanism 완전히밝혀지지않음.완전히밝혀지지않음 균일부식은동시에나타나지않음 activation/passivation interaction과관련있는것으로생각됨p 과관련있는것 생각됨 Stress raisers (trench, pit)

Typesyp TGSCC IGSCCIGSCC

145TGSCC of SS after autoclave testing in 1000 ppm chloride solution at 250oC

Stress

SCC

No SCC

SCC

Strain

147

세가지인자의결합작용 재료내부의인장응력

Materials Environment 부식성환경 (Cl-, H2S, etc) 고온

SCC환경예

CompositionHeat TreatmentMicrostructureSurface Condition

Corrosion

Environment

CompositionTemperatureElectrode PotentialFlow rate

SCC환경예 Acid chloride solution Seawater

Fatigue Corrosion-Fatigue

SCC

Stress, Strain

Condensing steam from chloride waters H2S + chloride

,

Service StressFit-up StressResidual StressStrain Rate

Polythionic acid (sensitized material) NaCl – H2O2

NaOH - H S NaOH - H2S

148

Statically loaded smooth specimen

• U-bend• C-ring• bent beam• direct tension specimen

Threshold stress(th) or critical cracking stress: - the max. stress below which SCC does not occur.- determined from the plot of applied stress vs. time

149

to failure

ASTM G30 Standard Practice for Makin

g and Using U-Bend Stress-Corrosion Test Specimens

150

ASTM G38 Standard Practice for Making and

U i C Ri St C i TUsing C-Ring Stress Corrosion Test Specimens

볼트를체결하여시편외면에인가되는인장응력에의한constant-strain(load)을인가

151

ASTM G39 Standard practice for p

preparation and use of bent-beam stress-corrosion test

ispecimens

152

ASTM G49 Standard Practice for Preparation p

and Use of Direct Tension Stress-Corrosion Test Specimens

153

Fracture mechanics testing 주어진응력조건및결함크기에서의균열성장속도에대한정보제공 Constant load조건또는고정된 crack opening displacement 조건에서실시, da/dt측정Constant load조건또는고정된 crack opening displacement 조건에서실시, da/dt측정

Stress Intensity, KISCC

154

SCC를조장하는전기화학(부식)반응의특성에큰영향을미치므로환경선정이을미치므로환경선정이SCC가속화에큰역할담당 수용액중의이온농도 수용액중의이온농도 전위 (potential) pHp 기체상의종류및분압 온도등실제환경 실험실환경 실제환경 vs. 실험실환경

156Cantilever beam specimen (PH13-8Mo) after SCC testing

ASTM G36 Standard Practice for

Evaluating Stress-Corrosion-Cracking Resistance of M t l d All i B ili Metals and Alloys in a Boiling Magnesium Chloride Solution ▪ 42~45% MgCl 154 155oC▪ 42~45% MgCl2, 154-155oC

Wrought, cast, welded ASS 및 Ni계합금에적용가능및 Ni계합금에적용가능

Chloride-SCC 저항성확인

157

ASTM G123 Standard Test Method for Evaluating Stress-Corrosion Cracking of g g

Stainless Alloys with Different Nickel Content in Boiling Acidified Sodium Chloride Solution (25% NaCl)

U-bend specimen ASTM G36 Standard Practice for Determining the Susceptibility of Stainless

Steels and Related Nickel-Chromium-Iron Alloys to Stress-Corrosion Cracking in Polythionic AcidsCorrosion Cracking in Polythionic Acids▪ As-received condition▪ After high-temperature service (480-815C)After high temperature service (480 815C)

159

250

s/1021.2 6

200304 stainless steels

50oC, 4 M NaCl

Pa)-100

0 E pit = -54 mV

-110 mV

-10 mV

100

150

Stre

ss (M

P

Air

-300

-200

-310 mV

-210 mV

Pot

entia

l(mV

)

Erp =-250 mV

0

50

S

-10 mV

-210 mV-230 mV -270 mV, -310 mV

No SCCSCC

10-3 10-2 10-1 100 101 102 103

-500

-400

-510 mV

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.70

Strainsevere dissolution

160

인장시험기를이용하여부식환경에노출된smooth 시편을느린 cross head speed(10-5 - 10-9 m/s)로p ( )인장시킴

합금의 SCC 저항성 [부식성환경에서의 strain]/[Inert환경에서의 strain]

161

ASTM G129 Standard Practice for Slow Strain Rate Testing to Evaluate the g

Susceptibility of Metallic Materials to Environmentally Assisted Cracking

ISO 7539 7 ISO 7539-7 Corrosion of metals and alloys – stress corrosion testing – Part 7:

Sl St i R t T tiSlow Strain Rate Testing Others

M difi d I d Modified Industry spec.

163

Oil and gas well (and/or refinery process)의부식성 Cl-, CO2, H2S, 2, 2

CO2 단독으로도 CS의큰부식을유발할수있으며, chloride가존재하면부식은더욱가속화

Sour environment Partial pressure of H2S > 0.05 psi. Liquid water (>50ppm H2S, refinery, NACE 8X194) More acidic, iron sulfide film formingg Hydrogen embrittlement (e.g., HIC) Sulfide stress cracking (SSC)g ( )

165

금속표면에수소원자가흡착할수있는환경에금속이노출되어유발되는속이노출되어유발되는기계적특성의저하현상

Hydrogen embrittlementHydrogen embrittlement Hydrogen blistering Hydrogen attackHydrogen attack Hydride formation

167

수소의 source Weldingg Electroplating & pickling

▪ 2H+ + 2e- H2 or 2H2O + 2e- H2 + 2OH-

Contact with gaseous hydrogen Corrosion (sulfide, cyanide)

168

강의 tensile ductility 감소

Hydrogen Induced Cracking (HIC) Internal cracking of lower strength steels (e.g. pipeline steels) due g g ( g p p )

to high pressure hydrogen collecting at inclusions. 잔류응력이나인장응력은필요조건이아님

Hydrogen Cracking Internal cracking of steels at higher temperatures due to reaction

of dissolved hydrogen with carbon to form methane

169

HH HHH

H

HH

HH

H

1 Hydrogen produced by the cathodic reaction1 Hydrogen produced by the cathodic reaction

2 Hydrogen diffuses to region of tri-axial tensile stress ahead of the crack

3 Hydrogen causes brittle fracture

4 Crack blunts by plastic deformation as it runs out of4 Crack blunts by plastic deformation as it runs out ofhydrogen

Cold cracking/HAZ cracking 수소의 source

M i t Moisture Organic compounds

용접후약 72시간후에발생용접후약 72시간후에발생 H원자의금속내확산속도 At 450F, 1 inch/hr At 220F, 1 inch/48hr 상온, 2주

방지 방지 용접표면에서습기제거 PWHT (400-450F 1h)PWHT (400 450F, 1h)

172

고강도강의수소취화저항성을평가 용액

▪ 5% NaCl + 0.5% acetic acid (pH 3.5) with H2S being continuously bubbled through the solution.

▪ A synthetic seawater solution saturated with H2S▪ pH: 2.70.1▪ H2S 농도최소 2300ppm시험시간 1h H S i 96h t ti 25 3C 시험시간: 1h H2S purging + 96h testing, 25±3C

실제환경을모사하기보다는 HIC 저항성을짧은시간에평가하기위한신뢰성/재현성있는시험환경을제공할목적위한신뢰성재현성있는시험환경을제공할목적

표준자체에 acceptance criteria는없음

S와 P의양제한, Ca비율준수실패시 HIC시험

178Shell DEP

a.k.a., Sulfide Stress Corrosion Cracking (SSCC) Sulfide가존재하는환경에서발생하는 SCC Sulfide는수소발생을억제하는 poisoner 수소원자의결합을억제수 원자의결합을억제

인자인자 Low pH CO2CO2

Stress Amb. Temperature (-7 to 49C)Amb. Temperature ( 7 to 49C)

179

Material requirement: NACE MR0175/MR0103 경도, 조성, 열처리등경 , 성,열처리등

새로운합금은 NACE TM0177의시험을통과해야.

180

용액 A: 5% NaCl + 0.5% Acetic acid, H2S saturated

▪ 특별히정해지지않았으면 A C D 시험은용액 A로특별히정해지지않았으면, A, C, D 시험은용액 A로 B: 5% NaCl + 2.5% Acetic acid + 0.41% NaCH3COO, saturated with

hydrogen sulfide (for CS & low alloy steel) C: 5mM Na NaCH COO + 실제환경과같은농도의 Cl- for MSS C: 5mM Na NaCH3COO + 실제환경과같은농도의 Cl- for MSS 실제 sour 유정/가스정의환경보다산성환경

온도및시간 24 3C 720h 온도및시간: 243C, 720h 시험법 Method A—Standard Tensile TestMethod A Standard Tensile Test Method B—Standard Bent-Beam Test Method C—Standard C-Ring Test

M th d D St d d D bl C til B (DCB) T t Method D—Standard Double-Cantilever-Beam (DCB) Test

183

Method A Time to failure The chemical composition, heat treatment, mechanical properties

Method B Method B Fail /no-fail data and pseudo stress values Time to failure (optional) Calculated critical stress (Sc)Calculated critical stress (Sc) The chemical composition, heat treatment, mechanical properties

Method C Fail / no-fail data from each stress level Time to failure (if it is recorded) The chemical composition, heat treatment, mechanical properties

Method DAll individual value of K for each set of specimens All individual value of KISCC for each set of specimens

Arm displacement The chemical composition, heat treatment, mechanical properties

184

Hydrogen induced cracking (HIC) tests NACE TM0284-96Sulfide stress corrosion cracking (SSCC) tests: Sulfide stress-corrosion cracking (SSCC) tests: NACE TM0177-96, EFC 16

▪ Constant load tensileConstant load tensile▪ Four-point bend▪ C-ring

Slow strain rate test▪ Slow strain-rate test Full Ring Tests: OTI 95 635 Autoclave testing of organic coatings: g g g NACE TM0185-93

Testing of elastomeric materials: C NACE TM0187-93, TM0296-96

186

UK HSE Offshore Technology Report, 1996 A Test Method to Determine the Susceptibility to Cracking p y g

of Linepipe Steels in Sour Service TM0177/TM0284와달리잔류응력효과검증가능와달리 류응력 과검증가능

▪ Full section of pipe를이용한시험을통해서배관제조및원주용접시, 보수작업등에서형성된잔류응력존재 (level & direction)

F ll l 압력시험 Full scale 압력시험 실제현장조건과같은방향의응력조건최대설계압력인가/고온시험도가능인가/고온시험도가능

ISO 15156/ NACE MR0175에 option으로포함됨

187

Full ring test에의해서발생한원주용접부의 SSC (예)

191

g 에의해서발생한원주용접부의 (예)

Refinery plant의 hydroprocessingequipmentSS SS clad or weld overlay steep plate

특징 특징 Bond/fusion line또는바로인근에서의 blister의형성/delamination

High T, High pressure of hydrogen 공정변화, shutdown, start-up으로인한급냉조건에서

ASTM G146시험에의해서형성된 HID & 균열인한급냉조건에서

ASTM G146 Standard Practice for

E l ti f Di b di f Evaluation of Disbonding of Bimetallic Stainless Alloy/Steel Plate for Use in High-Pressure, High-Temperature Refinery Hydrogen Service

고온의수소환경에고온의수소환경에bimetallic 시편노출▪ 정유공장에서발생하는

hydrogen charging conditionhydrogen charging condition재현

초음파검사로

194

초음파검사

195

Accelerated tests to demonstrate products durability Acceptance tests to show that a material meets standard

M it i t t t h h i t i it Monitoring tests to show changes in a system corrosivity Research tests to determine mechanism of corrosion

Usually corrosion tests have many parameters Corrosion tests often give results that are difficult to g

reproduce – Standardization helps reproducibility

• Industries dealing with corrosive situations• Engineers and designers g g• Governments specifying materials for projects• Academics teaching how to use materials in the real worldg

M G F t C i E i i 3rd d M G Hill N Y k 1986 1. M.G. Fontana, Corrosion Engineering. 3rd ed., McGraw-Hill, New York, 1986. 2. Webpage of Department of Chemical Engineering, University of New Brunswick, http://www.unene.ca3. L.L. Shreir, R.A. Jarman and C.T. Burstein, Corrosion: Metal/Environment Reactions, 3rd ed.,

Butterworth-Heinemann, Oxford, UK, 2000.H H Uhli d R W R i C i d C i C l 3 d d Wil & S N Y k 1984. H.H. Uhlig and R.W. Revie, Corrosion and Corrosion Control. 3rd ed., Wiley & Sons, New York, 1985

5. R. Bhaskaran, N. Palaniswamy, and N.S. Rengaswamy, Global cost of corrosion - A historical review, in Corrosion: Materials, Vol. 13B, ASM Handbook. ASM International., 2005

6. Corrosion Doctors Website, http://www.corrosion-doctors.org7. www.rolledalloy.co.uk8. Corrosion Tests and Standards, Application and Interpretation, 2nd ed., R. Baboian, ed., ASTM

International, PA, 2005.9. Corrosion: Fundamentals, Testing, and Protection, Vol. 13A, ASM Handbook. ASM International., 2003g10. Webpage of Sumitomo Metal Technologies, Inc., http://www.smt-inc.co.jp11. Webpage of JFE Techno-Research Corp., http://www.jfe-tec.co.jp12. http://corrosion.kaist.ac.kr13. http://www.sandvik.comp14. D.R. Askeland, The Science and Engineering of Materials, 4th ed., Ch.22: Corrosion and Wear.15. Product Finishing, Modern Plating Corporation, 2005.16. R.G. Kelly, J.R. Scully, D.W. Shoesmith & R.G. Buchheit, Electrochemical Techniques in Corrosion Sc

ience and Engineering, Marcel Dekker, Inc., 2002.ience and Engineering, Marcel Dekker, Inc., 2002.17. D.A. Jones, Principles and Prevention of Corrosion, Maxwell McMillian, New York, 1992.18. Cf. T. Arai, M. Mayuzumi and J. Ohta, SCC Maps for Low-alloy Steels by SSRT Method, Corrison/98,

98140, NACE International, TX, 1998.19 A test method to determine the susceptibility to cracking of linepipe steels in sour service OTI 95 635 19. A test method to determine the susceptibility to cracking of linepipe steels in sour service, OTI 95 635,

Health and Safety Exective, UK, 1996.

corrosion tests and standards

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