24291 predicting equip lifetime - high t corr

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Predicting Equipment Lifetimes with High Temperature Corrosion Data

R.C. John1, A.D. Pelton2, A.L. Young3, W.T. Thompson4, andI. G. Wright5

1Shell Global Solutions (US) Inc., P. O. Box 1380, Houston, Texas 77251-1380 USA, phone 281-

544-7229, fax 281-544-6060, [email protected], Ecole Polytechnique de Montréal, 447 Berwick, Montreal H3R 1Z8 Canada, phone 514-

340-4711, fax 514-340-5840, [email protected] Solutions Ltd., Suite 1410, 270 Scarlett Road, Toronto, Ontario M6N 4X7 Canada,

phone 416-769-4200, fax 416-769-6650, [email protected] Military College of Canada, Kingston, Ontario, K7K 5LO Canada, phone 613-544-6159, fax

613-544-7900, [email protected] Ridge National Laboratory, P. O. Box 2008, MS-6156, Oak Ridge, Tennessee 37831-6156

USA, phone 865-574-4451, fax 865-241-0215, [email protected]

Keywords: ASSET, sulfidation, high-temperature corrosion predictions, corrosion datacompilation, engineering lifetime predictions, weight change, parabolic rate constant

Abstract. This presentation summarizes the on-going development of an information system used

to predict corrosion of metals and alloys by high temperature gases found in many different oil

refining, petrochemical, power generation, and chemical processes. The databases currently

represent about 13 million hours of exposure time for about 7,800 tests with 90 commercial alloys

for a temperature range of 200 – 1,200oC. The data are the result of tests with well-defined

conditions lasting thousands of hours. Oxidation has been emphasized with many exposures lasting

several years of time. The corrosion data archived and the resulting corrosion predictions represent

total metal penetration, which includes both surface recession and subsurface corrosion. The system

manages corrosion data from well-defined exposures and determines corrosion product stabilities.

Models used in the thermochemical predictions of corrosion product phase stabilities for all

possible phases formed from combinations from the Fe-Ni-Cr-Co-C-O-S-N-H system have been

compiled. Thermochemical data for all of the known phases based upon combinations of these

elements have been analyzed to allow complete assessments of corrosion product stabilities. Use of

these data allows prediction of corrosion product stabilities predicted to form at the scale/gas

interface, which can then be used to infer the dominant corrosion mechanisms. Previous

approaches, which have often used simplifying assumptions of pure and single component

corrosion products, are no longer required. The stabilities of complex corrosion product phases orreal alloys can now be calculated, assuming equilibrium. The system is used in corrosion research,

alloy development, failure analysis, lifetime prediction, and selection of materials/alloys for

equipment fabrication, equipment maintenance scheduling, and process operations evaluations. The

corrosion mechanisms emphasized are oxidation, sulfidation, sulfidation/oxidation, carburization,

and nitridation. The capabilities for managing corrosion data for Cl2 /HCl corrosion, metal dusting,

and cyclic oxidation are under development.

Background

This paper discusses the development of a technology to predict corrosion of metals and alloys inhigh-temperature gases by several different corrosion mechanisms. The corrosion mechanisms,

which are well developed, are oxidation, sulfidation, sulfidation/oxidation, and carburization. The

Materials Science Forum Vols. 461-464 (2004) pp. 599-610online at http://www.scientific.net © (2004) Trans Tech Publications, Switzerland

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capabilities are now being developed to predict corrosion by HCl/Cl2 corrosion, metal dusting, and

cyclic oxidation. The capability to predict corrosion of commercial alloys by these mechanisms will

have far-reaching implications in many different industries, including processes used in petroleum

refining, gas processing, fired equipment, process heaters, thermocouples, instrumentation,

hydrocracking, coking, vacuum flashing, hydrotreating, coal/coke/oil gasifying, petrochemical

production, catalytic reforming, power generation and gasification of black liquor in pulp/paperproduction. Applications for this technology are found in industries such as oil refining,

petrochemicals production, pulp/paper production, and power generation.

Corrosion often defines the maximum allowable temperature or maximum allowable gas species

concentrations for metals and alloys in equipment, although mechanical properties or other

considerations may also define the maximum allowable temperature. The data compilation now

allows engineering corrosion assessments for sulfidation and sulfidation in the presence of

oxidizing gases and predictions for wide ranges of conditions. The effects of gas composition,

temperature, exposure time and alloy type have all been analyzed and compiled to allow prediction

of corrosion for wide ranges of conditions to allow engineering predictions of corrosion-limited

lifetimes.

Most corrosion data for alloys exposed to high-temperature gases are reported in terms of weight change/area for relatively short exposures and inadequately defined exposure conditions.

Unfortunately, the weight change/area information is not directly related to the thickness

(penetration) of corroded metal, as illustrated in Fig. 1 and is often needed in assessing the strength

of process equipment components. Corrosion is best reported in penetration units, which indicate

the sound metal loss, as discussed earlier1-2

. Corrosion in high-temperature gases is affected by key

parameters of the corrosive environments such as temperature, alloy composition, time, and gas

composition. Examples of metal penetrations for some typical conditions are shown in this

presentation. Compositions of some of the alloys discussed in this paper are shown in Table 1.

Studies on alloy oxidation, in terms of

penetration measurement, have been reported formany years

1-10. Most studies, which have reported

systematic investigations of the effects of exposure

conditions, such as gas composition, temperature,

and time upon oxidation, have emphasized simple,

model alloys. Typical exposure times have been

hundreds and rarely to thousands of hours. These

studies have often indicated the amount of

oxidation with a measure of the weight change or

weight change/area of the alloy sample

corresponding to the incorporation of corrosive

species into the alloy corrosion products. Thisapproach infers a relationship between the weight

change of the affected alloy to the thickness of

sound metal loss, assuming that the weight change

corresponds to a uniform layer, such as a surface

scale of a corrosion product. This assumption is

often been true for model alloys, which form surface scales as the primary corrosion product.

However, demonstration of this approach for a variety of commercially used, heat resistant, alloys

has not been well established in public literature. A common motivation to measure the corrosion

behavior of metals is to determine the extent or rate of metal penetration because the utility of most

high temperature equipment depends upon the materials of construction having sufficient

uncorroded metal to provide the required load-bearing strength to function in the structure.

Figure 1. Schematic View of Total Penetration

Measurement, which is the corrosion

measurement archived and Used in ASSET, for a

Typical Corrosion Product Morphology.

uncorroded

alloy

total

penetrationinternal

penetration

external scale

internal

corrosionproducts

corroded grainboundaries

Figure 1. Schematic View of Total Penetration

Measurement, which is the corrosion

measurement archived and Used in ASSET, for a

Typical Corrosion Product Morphology.

uncorroded

alloy

total

penetrationinternal

penetration

external scale

internal

corrosionproducts

corroded grainboundaries

High Temperature Corrosion and Protection of Materials 6600



Determination of the total metal penetration is a good assessment of an alloy's suitability for

engineering application in a particular set of exposure conditions.

An objective of this study was to produce alloy oxidation data, which could be used to predict

the extent of sound metal loss as a result of oxidation occurring over ranges of conditions present in

real high temperature equipment. The approach emphasized exposures to ranges of practical

variables pertinent to operating equipment. Exposure times ranged up to nearly 24,000 hr withvariations in the O2 concentrations from 0.1 to 100% in O2-N2 gases, and temperatures of 200 -

1200oC. The metal penetration was determined for all of the samples exposed. The total penetration

reported in this study is the sum of the surface scale plus the internal penetration.

Table 1. Compositions of Some Alloys in this Study

Alloy Name UNS Fe Cr Ni Co Mo Al Si Ti W Mn Cu RE* C Nb

153 MA S30415 69.66 18.30 9.50 0.00 0.42 0.00 1.23 0.00 0.00 0.56 0.23 0.05 0.05 0.00

253 MA S30815 65.60 20.90 11.00 0.00 0.00 0.00 1.77 0.00 0.00 0.64 0.00 0.00 0.09 0.00

AISI 1020 G10200 99.42 0.00 0.00 0.00 0.00 0.00 0.04 0.00 0.00 0.38 0.00 0.00 0.16 0.00

AISI 304 S30400 71.07 18.28 8.13 0.14 0.17 0.00 0.49 0.00 0.00 1.48 0.19 0.00 0.05 0.00AISI 310 S31000 52.41 24.87 19.72 0.05 0.16 0.00 0.68 0.00 0.00 1.94 0.11 0.00 0.06 0.00

AISI 316 S31600 68.75 17.00 12.00 0.00 2.25 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

AISI 410 S41000 86.50 12.30 0.50 0.00 0.10 0.00 0.60 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Alloy 188 R30188 1.32 21.98 22.82 38.00 0.00 0.00 0.37 0.00 14.55 0.82 0.00 0.04 0.10 0.00

Alloy 214 N07214 2.49 16.04 76.09 0.14 0.10 4.71 0.10 0.00 0.10 0.20 0.00 0.00 0.03 0.00

Alloy 230 N06230 1.30 21.90 59.70 0.28 1.20 0.38 0.42 0.02 14.20 0.49 0.01 0.00 0.10 0.00

Alloy 556 R30556 32.50 21.27 21.31 18.09 2.88 0.17 0.33 0.00 2.38 0.96 0.00 0.00 0.11 0.00

Alloy 600 N06600 7.66 15.40 75.81 0.00 0.00 0.32 0.16 0.00 0.00 0.29 0.32 0.00 0.04 0.00

Alloy 601GC N06601 13.53 23.48 60.00 0.06 0.16 1.26 0.50 0.27 0.00 0.31 0.38 0.00 0.05 0.00

Alloy 617 N06617 0.76 22.63 53.20 12.33 9.38 1.15 0.15 0.27 0.00 0.02 0.05 0.00 0.06 0.00

Alloy 625 N06625 2.66 21.74 62.79 0.00 8.46 0.10 0.41 0.19 0.00 0.10 0.00 0.00 0.03 3.52Alloy 800 H N08810 44.22 21.22 31.71 0.00 0.00 0.33 0.60 0.41 0.00 0.92 0.51 0.00 0.08 0.00

INCOLOY 803** 35.94 26.19 35.04 0.21 0.01 0.58 0.63 0.33 0.00 0.98 0.00 0.00 0.09 0.00

INCOLOY DS 44.31 16.60 34.90 0.00 0.29 0.00 2.52 0.00 0.00 1.14 0.17 0.00 0.07 0.00

Copper C11000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 100.00 0.00 0.00 0.00

HR-120 N08120 34.53 25.12 37.44 0.11 0.37 0.11 0.57 0.02 0.10 0.73 0.18 0.00 0.06 0.66

HR-160 N12160 8.00 28.00 34.30 27.00 0.00 0.00 2.70 0.00 0.00 0.00 0.00 0.00 0.00 0.00

INCOLOY

MA956

S67956 75.22 19.40 0.28 0.05 0.00 4.50 0.11 0.33 0.00 0.09 0.00 0.00 0.02 0.00

Nickel N02270 0.00 0.00 99.99 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.00

602 CA N06025 9.45 25.35 62.63 0.00 0.00 2.09 0.06 0.14 0.00 0.09 0.01 0.00 0.18 0.00

• RE means rare earth elements• ** INCOLOY is a trademark of Special Metals Corporation

Corrosion mechanisms

For all mechanisms in this study, the name of the mechanisms comes from the corrosion products,

which dominate. Examples are: oxides form during oxidation, carbides form during carburization

and so on. Corrosion by these mechanisms leads to formation of corrosion products, leads to metal

loss (penetration), and occurs upon exposure of metals to gases which contain the reactive species

need to form the corrosion products. An X-ray analysis by diffraction of a surface scale sample is a

common method to determine the identity of corrosion products. An alternate method is to evaluatethe gas composition. Surface metal loss (scaling) can be detected by methods, which measure the

Materials Science Forum Vols. 461-464 601



metal thickness, such as ultrasonic and mechanical methods. Sound metal loss by internal corrosion

can only be detected by metallography, as schematically shown in Fig. 1.

The time dependence of high temperature corrosion is controversial3-5

and depends upon the

combination of alloy, temperature, time, and corrosion mechanism. Reported time dependencies

include: parabolic (metal loss proportional to time0.5

), linear (metal loss proportional to time),

power law (metal loss proportional to time

x

), and various combinations of these dependencies. If thecorrosion product scale remains undisturbed on the alloy surface and sufficient time has passed (in

excess of 1,000 hr), a reasonable approximation is that the time dependence is parabolic. Removal

or cracking of the surface scale will tend to increase the rate of corrosion, because the presence of

the scale is a partial barrier, which will tend to slow the corrosion rate as time passes, but corrosion

still continues. Some studies suggest an initial linear time dependence for several thousand hours.

Corrosion data measured after hundreds of hours (as is often the case for available data) is unlikely

to be useful in estimating sulfidation corrosion rates for long-term service. Corrosion data are

properly used when the time dependence is considered. The corrosion mechanisms considered in

this presentation and some of the important variables are listed below:

Oxidation. The key variables, which influence the kinetics, are the exposure time, and partialpressure of O2, alloy composition and temperature.

Sulfidation. The key variables, which influence the kinetics, are exposure time, partial pressures of

H2 and H2S (for H2 and H2S gases) or CO and COS for (CO - COS gases), alloy composition and

temperature.

Sulfidation/oxidation. The key variables, which influence the kinetics, are exposure time, partial

pressures of O2 and S2, alloy composition and temperature.

Carburization. The key variables, which influence the kinetics, are exposure time, partial pressure

of H2S, activity of carbon, alloy composition and temperature.

HCl/Cl2 corrosion. The key variables, which influence the kinetics, are exposure time, partial

pressure of HCl and Cl2, alloy composition and temperature.

Metal dusting. The key variables, which influence the kinetics are controversial but certainly

include exposure time, stability of surface films such as oxides or sulfides, surface condition (such

as annealed or cold worked), alloy composition and temperature.

Cyclic oxidation. The key variables, which influence the kinetics, are exposure time, thermal cycle

features, partial pressure of O2 and alloy composition.

The data collection allows corrosion predictions to be made for about 90 commercial alloys

shown, with some examples listed in Table 1. The progressive accumulation of this data over time

is illustrated in Fig. 2 in terms of the total number of exposure hours represented by the data.

The current testing efforts are generating and compiling data for the following conditions:

• Cl2 /HCl corrosion testing in air + Cl2, air + HCl, and N2+Cl2 /HC (l - 30 % Cl2 and 0 - 30 %

HCl), at 200 - 900°C,

• Cyclic oxidation testing of 10 alloys in air environments and other gases at 800 -1,200°C.

• Metal dusting data compilation from numerous sources.

Effect of Exposure Time Upon Oxidation. Many alloys tend to have linear dependencies of

penetration with time0.5

, after sufficient time has passed, as illustrated for some alloys in Fig. 3. The




dotted lines suggest the approximate slopes corresponding to that expected for parabolic time

dependence. However, it was surprising to discover that alloys, which form Al2O3-rich, surface

scales showed no time dependence. The amount of oxidation did not increase with the passage of

time, even as long as 24,000 hr. at 982oC in air! Obviously, higher temperatures are needed to

induce increasing scale growth.

0

2,000,000

4,000,000

6,000,000

8,000,000

10,000,000

12,000,000

14,000,000

7-1996 1-2000 3-2001 8-2001 3-2002 9-2002 4-2003 12-2003

ASSET Software Release Date

E x p o s u r e T i m e ,

h r

Total CarburizationCyclic Oxidation Isothermal OxidationIsothermal Oxidation with SO2/SO3 SulfidationSulfidation / Oxidation Sulfuric/Sulfurous Acid Dew Point Corrosion

Figure 2. Growth of ASSET Database Exposure Time

0

2,000,000

4,000,000

6,000,000

8,000,000

10,000,000

12,000,000

14,000,000

7-1996 1-2000 3-2001 8-2001 3-2002 9-2002 4-2003 12-2003

ASSET Software Release Date

E x p o s u r e T i m e ,

h r

Total CarburizationCyclic Oxidation Isothermal OxidationIsothermal Oxidation with SO2/SO3 SulfidationSulfidation / Oxidation Sulfuric/Sulfurous Acid Dew Point Corrosion

Figure 2. Growth of ASSET Database Exposure Time

The amount of metal penetration by internal oxidation as the exposure time increases was also

studied. The alloys tended toward most of the penetration occurring as internal oxidation at longtimes, with most of the alloys showing about 80-95% of the penetration as internal oxidation.

Alloys with Al2O3-rich scales showed no change in the relative amount of penetration by internal

oxidation with the progression of time. Although some of the alloys did change in their relative

amounts of penetration occurring by internal oxidation, the corrosion product morphologies were

not obviously different as the exposure time increased. The alloys with Fe and Cr-rich surface

scales tended towards large amounts of internal oxidation, while alloys with Al2O3-rich scales

showed very little internal oxidation.

Effect of temperature upon oxidation. The alloys tended to have more penetration with increasing

temperature for all of the O2 concentrations studied. Examples are shown in Fig. 4 for exposures to

air for 1,000 hr. Most of the alloys had relative amounts of penetration by internal oxidation to beindependent of temperature and O2 concentration as the temperature increased, during exposures to

gases of 0.1, 1, 21 and 100% O2. Alloys that form Cr2O3 scales often had relative amounts of

penetration by internal oxidation in excess of 80%. Examples are: S31000, N08810, N18120,

N07214, N06601, N06025, S44600, N06230, N06617, and S30400. Alloys that form Al 2O3 scales,

like S67956, N07214, N06025, FA320, and FAL had most of the penetration occurring by surface

scale formation.

The results also show that the relative amount of penetration occurring as internal oxidation

changed most with temperature during exposure to 1% O2 and became less dependent upon

temperature as the O2 concentration increased. The greatest variation in the amount of internal

oxidation for variation of temperature was observed for exposures to 1% O2. Higher temperatures

and higher O2 concentrations tended to promote less variation in penetration and increased relativeamounts of penetration occurred as internal oxidation. A potential explanation for this behavior is




that low temperatures and low O2 concentrations are conditions in which oxide surface layers are

less likely to form and all of the alloying elements will oxidize together, making many of the alloys

marginally resistant to oxidation in low O2 concentrations. Increased temperatures and O2

concentrations could favor formation of the very oxidation resistant surface scales and thereby

reduce the differentiation among the alloys and also cause greater internal oxidation as the reactive

elements in low concentrations oxidize underneath the surface scales more rapidly than thesurrounding base metal.

S31000

0

1

10

100

100 1000 10000 100000

Time, hr

P e n e t r a t i o n , m i l

720 C 871 C 982 C

N07214

0.1

1.0

10.0

1000 10000Time, hr

P e n e t r a t i o n , m i l s

982 C

N06230

0.1

1.0

10.0

100.0

100 1000 10000Time, hr


982 C

N06025

0.1

1.0

10.0

100 1000 10000Time, hr


982 C

Figure 3. Effect of Time Upon Penetration of Alloys Exposed to Air at 982 C.

Figure 4. Effect of Temperature Upon Penetration for Alloys Exposed to Air for 1,000 hr.

0.1

1.0

10.0

100.0

300 500 700 900 1100Temperature, C


Copper Carbon Steel Nickel

0.1

1.0

10.0

100.0

700 900 1100 1300Temperature, C


Incoloy 803 N06600 S31000

S31000

0

1

10

100

100 1000 10000 100000

Time, hr

P e n e t r a t i o n , m i l

720 C 871 C 982 C

N07214

0.1

1.0

10.0

1000 10000Time, hr


982 C

N06230

0.1

1.0

10.0

100.0

100 1000 10000Time, hr


982 C

N06025

0.1

1.0

10.0

100 1000 10000Time, hr


982 C

Figure 3. Effect of Time Upon Penetration of Alloys Exposed to Air at 982 C.

Figure 4. Effect of Temperature Upon Penetration for Alloys Exposed to Air for 1,000 hr.

0.1

1.0

10.0

100.0

300 500 700 900 1100Temperature, C


Copper Carbon Steel Nickel

0.1

1.0

10.0

100.0

700 900 1100 1300Temperature, C


Incoloy 803 N06600 S31000

Every alloy formed surface scales of oxides at the P O2’s used in this study (0.0001 – 1.0 atma).

Surface scales in the absence of subsurface oxidation products were rarely observed, except for

Al2O3-forming alloys. The alloys varied greatly in the extent and type of subsurface corrosion. The

alloys generally exhibited the majority of metal penetration by a combination of internal oxidationand void formation. The morphology of surface scale formation + intergranular oxides was the most

common. Most of the penetration occurred by internal oxidation along grain boundaries and internal




to the grains. The surface scales were often made of (Cr, Fe) oxides, with the concentration of Fe

increasing with the O2 concentration. Internal corrosion products were often oxides rich in reactive

elements such as Ti, Si, Cr and Al.

S31000

0.1

1.0

10.0

0.001 0.010 0.100 1.000P O2, atma

P e n e t r a t i o n , m m

760 C 871 C 982 C 1093 C

N07214

0.1

1.0

10.0

100.0

0.001 0.010 0.100 1.000P O2, atma


982 C 1093 C

R30556

0.1

1.0

10.0

0.001 0.010 0.100 1.000P O2, atma


982 C

Figure 5. Effect of P O2 Upon Metal Penetration for AlloysExposed to Several Temperatures 1,000 hr

S31000

0.1

1.0

10.0

0.001 0.010 0.100 1.000P O2, atma


760 C 871 C 982 C 1093 C

N07214

0.1

1.0

10.0

100.0

0.001 0.010 0.100 1.000P O2, atma


982 C 1093 C

R30556

0.1

1.0

10.0

0.001 0.010 0.100 1.000P O2, atma


982 C

Figure 5. Effect of P O2 Upon Metal Penetration for AlloysExposed to Several Temperatures 1,000 hr

Effect of oxygen concentration upon oxidation. The influence of O2 concentration upon oxidation

is complex over the temperature range of 871 – 1177oC. The approach taken to view the data was to

examine the differences of the penetration between the alloys for different O2 concentrations in the

gas phase at a constant exposure time of 1,000 hr. Comparing the graphs in Fig. 5 shows the

influence of O2 concentration with constant temperature upon penetration rates. The general

conclusion is that most alloys vary in the influence of the O2 concentration upon the penetration.Oxidation rates of most Cr2O3 – forming alloys such as S31600, S30415, N06230, FA320, N30556,

N06600, N06617, S50400, INCOLOY 803, FAL, N06025, INCOLOY DS, copper, and G10200

increase with P O2. Al2O3-forming alloys such as S67956, N07214, and N18120 exhibited slower

oxidation as the O2 concentration increased. These alloys with Al concentrations of 4.7 %

underwent less penetration as the O2 concentration of the ambient gas increased. Alloys like

S32100, S34700, N12160, nickel, and N06601 showed no influence of the penetration by the P O2.

Some alloys like S30400, S31000, and S41000 showed higher penetrations at higher P O2’s and

lower P O2’s, with a minimum at some intermediate P O2. Microstructures show that for these

alloys, penetration is mostly scale formation at high P O2’s, while internal oxidation dominates at

low P O2’s. The minimum in penetration at some intermediate P O2 is the result of the transition

between penetration domination by scale formation and by internal oxidation.




Predicting Corrosion Products on Real Alloys Via Thermochemical Calculations

Oxides-Sulfides-Carbides-Nitrides. Since there are many different types of alloys, which might be

used in a wide range of gases and could potentially induce corrosion in the presence of complex

gases, a general capability to predict the stabilities of corrosion products has been developed. Theapproach taken has been to use thermochemical calculations to predict the most stable corrosion

products, as defined by the alloy composition, gas composition, and temperature. The approach

considers a small amount of alloy exposed to a large amount of gas, with an assumed molar ratio of

1 mole alloy to 1,000 moles of gas. This is done to approximate the surface of a corroding alloy in

contact with a large amount of gas, as might be experienced by a surface of alloy equipment

exposed to large amounts of flowing gas. The approach assumes that only the majority elements in

the alloys will determine the dominant corrosion mechanism, as determined by the majority of

corrosion products, within these constraints, the calculations are very accurate, as described below.

Thermochemical models for the many complex corrosion product phases were developed to enable

the required calculations.

The elements considered in the thermochemical calculations are: W-La-Mo-Nb-Cu-Ni-Co-Fe-Mn-Cr-Ti-Ar-Cl-S-Si-Al-F-O-N-C-H. The thermochemical literature has been extensively reviewed

and models have been built to describe the solution thermodynamics of the complex sulfide, alloys,

carbides, oxides, nitrides and intermetallic phases have been constructed and are described

elsewhere30-32

. The elements which are considered to occur in the solution phases are:

• Al-Co-Cr-Fe-Mn-Ni-Si-Ti in the case of oxides:

Spinel - (Fe2+, Fe3+, Co2+, Co3+, Cr2+, Cr3+, Ni2+, Mg2+, Al3+) [Fe2+, Fe3+, Co2+, Co3+,

Cr3+, Ni2+, Mg2+, Al3+]2 O4

Corundum - Fe2O3 - Cr2O3 - Al2O3 Monoxide -

FeO - CoO - NiO - CaO - MgO - Al2O3 - ZnO – CuO Fe-Ni-Co-Crin the case of sulfides

• W-Mo-Nb-Cu-Ni-Co-Fe-Mn-Cr-Ti-Si-Al in the case of carbides and nitrides

• W-La-Mo-Nb-Cu-Ni-Co-Fe-Mn-Cr-Ti-Si-Al-N-C in the case of metallic alloy solution (liquid

and solid) phases

The effort included development of appropriate mathematical models, based upon the structure

of the solutions and described the thermodynamic properties as functions of temperature and

composition. The models were “optimized" by using all available thermodynamic and phase

diagram data from the literature (to obtain a set of model parameters for the 2-component, 3-

component and higher order sub-systems). The resulting models were used to estimate the

thermodynamic properties of the N-component solution from the database of parameters for lower-order sub-systems. The models were then evaluated by comparison to the available thermodynamic

and phase equilibrium data, which concluded that the model predictions can reproduce the

measured data within the experimental error limits from 25oC to above the liquidus temperatures at

all compositions and oxygen partial pressures from metal saturation to equilibrium with oxygen.

The model for the sulfide liquid phase contains Fe-Ni-Co-Cr-S and uses the Quasichemical Model

(Pair Approximation). For solid non-stoichiometric sulfide solutions in the Fe-Ni-Co-Cr-S system,

appropriate thermodynamic models were developed. Parameters of these models were optimized to

reproduce all solid-solid and solid-liquid phase equilibria. Examples of the evaluations of the

models are listed below:

•

Partial pressure of sulfur in the liquid sulfide over the whole composition range from puremetals to sulfur-rich liquid

• Metal activity data




• Metal-liquid sulfide equilibrium data

• Liquid oxide equilibrium data

All other thermodynamic data available for liquid and solid sulfides such as heats of mixing,

heat content, heat capacity, etc. were also considered in the development of the models.

Corrosion by HCl/Cl2 gases. All available thermochemical data will be analyzed to produce

consistent data sets after collection and modeling. Estimations may be made by a variety of

techniques. Databases for the multicomponent solid and liquid solution phases will be developed by

techniques of critical optimization. Model parameters for binary and ternary sub-systems are made

from available literature data and then models will estimate properties of multicomponent solutions.

For the liquid salt phase, we’ll use the quasichemical model and Compound Energy Formalism for

the solid product phases. Cases to be considered shall include corrosion of Fe-Co-Cr-Ni-C-N alloys

at 200 - 900oC and pressures up to 1 bar, in gases containing Cl2, O2, H2O, HCl, CO, CO2, N2, Cl,

O, C, H, and N for all compositions. Co-existence of Cl2 and S will not be considered. The database

will contain Cl-O-C-H-N-Fe-Co-Cr-Ni compounds. All oxidation states will be considered.

The solid and liquid halide database will include all oxidation states that may occur under theseconditions. Solid solutions and pure solids of chlorides and hydroxychlorides will be modeled. The

liquid chloride solution may contain the metal ions in more than one oxidation state, as well as

dissolved oxygen (or oxychlorides), hydroxide, and possibly carbonate. A database for the FeCl 2-

FeCl3-CoCl2-NiCl2 system (solid and liquid phases) is already being developed, including molten

salt, solid solutions, stoichiometric compounds, gaseous species and hydroxides/hydroxychlorides

in the molten salt at various P (H2O) and P (HCl)’s.

1.E-03

1.E-02

1.E-01

1.E+00

1.E+01

300 500 700 900

Temperature, C


S30400 N06600 N08810S30815 S44600 N12160

Figure 6. Effect of Temperature Upon Corrosion for Alloys Exposedto 5% H2S, 30% H2O, and 65% H2 at 10 atma after one year .

1.E-03

1.E-02

1.E-01

1.E+00

1.E+01

300 500 700 900

Temperature, C


S30400 N06600 N08810S30815 S44600 N12160

Figure 6. Effect of Temperature Upon Corrosion for Alloys Exposedto 5% H2S, 30% H2O, and 65% H2 at 10 atma after one year .




Figure 7. Calculated Corrosion Products for A Small Amount of Alloy Exposedto a Large Amount of 5% H2, 65% H2, and 30% H2O at One Atma.

N06600

0

20

40

60

80

100

0.1 1 10 100% Steam

P h a s e A m o u n t , M

o l e %

MeS(l) MeS(s)Me2O3 Me3S4

N12160

0

20

40

60

80

100

0.1 1 10 100% Steam

P h a s e A m o u n t , M o l e %

MeS(s) Me2O3 SiO2

N06600

0

20

40

60

80

100

0.01 0.1 1 10H2S, Mole %

P h a s e F r a c t i o n ,

M o l e %

MeS(l) Me2O3 Me3O4

Me3S2(s) Alloy

N12160

0

20

40

60

80

100

0.01 0.1 1 10H2S, Mole %


M o l e

%

MeS(l) Me2O3 Me3O4Alloy MeS(s) SiO2

Figure 8. Effect of H2S Concentration Upon Formation of Corrosion Products for Some

Alloys Exposed to X H2S, 60% H2, 30% H2O and Bal Ar At One Atma and 648o

C.

N06600

0

20

40

60

80

100

500 600 700Temperature, C

P h a s e A m o u n t , m o l e %

MeS(l) MeS(s) Me2O3

N12160

0

20

40

60

80

100


P h a s e A m

o u n t , m o l e %

MeS(l) MeS(s) Me2O3

Figure 7. Calculated Corrosion Products for A Small Amount of Alloy Exposedto a Large Amount of 5% H2, 65% H2, and 30% H2O at One Atma.

N06600

0

20

40

60

80

100

0.1 1 10 100% Steam

P h a s e A m o u n t , M

o l e %

MeS(l) MeS(s)Me2O3 Me3S4

N12160

0

20

40

60

80

100

0.1 1 10 100% Steam

P h a s e A m o u n t , M o l e %

MeS(s) Me2O3 SiO2

N06600

0

20

40

60

80

100

0.01 0.1 1 10H2S, Mole %


M o l e %

MeS(l) Me2O3 Me3O4

Me3S2(s) Alloy

N12160

0

20

40

60

80

100

0.01 0.1 1 10H2S, Mole %


M o l e

%

MeS(l) Me2O3 Me3O4Alloy MeS(s) SiO2

Figure 8. Effect of H2S Concentration Upon Formation of Corrosion Products for Some

Alloys Exposed to X H2S, 60% H2, 30% H2O and Bal Ar At One Atma and 648o

C.

N06600

0

20

40

60

80

100


P h a s e A m o u n t , m o l e %

MeS(l) MeS(s) Me2O3

N12160

0

20

40

60

80

100


P h a s e A m

o u n t , m o l e %

MeS(l) MeS(s) Me2O3

Predicting corrosion product formation of some alloys in sulfidizing/oxidizing conditions

The utility to predict formation of alloy corrosion rates and corrosion product formation is now

available, as shown in Figs. 6 - 8. The results compare very well with practical experience. Nickel-

base alloys will form mostly liquid nickel sulfide corrosion products, like N06600. Increasing the

amount of Cr will increase the amount of oxide of a nickel-base alloy (as found in N06025) but will

not prevent the formation of the liquid sulfide. An iron-base stainless, like S30400 does not form

liquid sulfide, but does form mostly solid sulfides. An alloy, like N12160, with low nickel

concentration and high concentrations of Cr and Si forms large concentrations of oxides and liquid

sulfide only at high H2S concentrations and high temperatures, which should be excellent for

resistance to corrosion in these conditions, as is the case for this alloy shown here.




Conclusions

This paper presents metal loss information for alloys in several types of corrosive environments and

shows how to categorize corrosive environments. The databases contain an extensive set of

corrosion data for commercial alloys and a wide range of exposure conditions at high temperatures.

This study has developed a capability to predict corrosion formation of the basic types of corrosionproducts and the capability to predict alloy corrosion kinetics for wide ranges of conditions.

• Most of the alloys underwent more than 80% of the sound metal loss (total penetration defined

as the sum of sound metal lost by scale formation and internal oxidation) as a result of internal

corrosion or void formation. Surface scale formation generally produced less than 20% of the

total penetration. The large amounts of alloy corrosion data available and reported as weight

change do not describe the sound metal loss is most cases.

• Many of the alloys eventually corrode according to a parabolic dependence with time after times

as long as 1,000 hr.

• Increased temperatures always resulted in more oxidation.

• The influence of P O2 upon alloy oxidation is complex and further work is needed for adequate

understanding.

Acknowledgements

Participation and support by the following organizations are recognized and appreciated: USDepartment of Energy – Office of Industrial Technologies via cooperative agreement DE-FC36-

03ID14505, Shell Global Solutions (US), Humberside Solutions Ltd., Centre for Research in

Computational Thermochemistry in Université de Montréal, Royal Military College of

Canada, Oak Ridge National Laboratory, Materials Technology Institute, Foster Wheeler

Development Corporation, KEMA, Caterpillar, Special Metals Corporation, Texaco, Haynes

International, Usinor Industeel, and Kvaerner Pulping Oy. The experimental testing effort owes itsdeepest gratitude to Owen Kriegel of Shell Global Solutions (US) Inc and research staff at ORNL.

Data contributions from Haynes International, VDM, and Special Metals Corporation are

acknowledged.

References

[1] R.C. John: Proceed. Second International Conference on Heat Resistant Materials, Gatlinburg,

TN, 11-14, Sept. 1995.

[2] R.C. John: CORROSION/96, Paper 171, National Association of Corrosion Engineers,Houston, Texas, 1996.

[3] E.W. Haycock: High Temperature Metallic Corrosion of Sulfur and Its Compounds, (ed. Z. A.

Foroulis), Electrochemical Society, Princeton, New Jersey, p. 110 (1970).

[4] E.W. Haycock and W.H. Sharp: Corrosion of Ferrous Alloys by H 2S at High Temperatures,

Session from the 24th

Meeting of the American Petroleum Institute, New York (1959).

[5] R.C. John, W.C. Fort III and R.A. Tait: Mater. High Temp. Vol. 11 (1993), p. 124

[6] R.C. John, A.L. Young and W.T. Thompson: CORROSION/97, Paper 142, National

Association of Corrosion Engineers, Houston, Texas (1997).

[7] G.Y. Lai: High-Temperature Corrosion of Engineering Alloys, ASM International, MaterialsPark, Ohio, 1990 and literature from Haynes International Marketing, "Technical Information,

Oxidation Resistance of Haynes High Temperature Alloys".




[8] J. Guzeit: High Temperature Sulfidic Corrosion of Steels, Process Industries Corrosion – The

Theory and Practice, National association of Corrosion Engineers, Houston, Texas (1986).

[9] E.B. Backensto, R.E. Drew and C.C. Stapleford: Corrosion - NACE Vol. 12 (1956), p. 22

[10] G. Sorell and W.B. Hoyt: Corrosion - NACE Vol. 12 (May 1956), p. 213t

[11] G.Y. Lai: CORROSION/84, Paper 73, National Association of Corrosion Engineers, Houston,

Texas, (1984). Plus data from brochures Haynes 188 and Pocket Guide to Haynes Alloys from

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[12] Stoklosa and J. Stringer: Oxid. Met. Vol. 11 (1977), p. 263

[13] P. Kofstad: High temperature Corrosion Elsevier Applied Science (1988).

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[15] J.F. Norton and W.T. Bakker (ed.): Materials for Coal Gasification Power Plant ,

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[16] W.T. Bakker, S. Dapkunas and V. Hill (ed.): Materials for Coal gasification, ASM

International (1988).

[17] J.D. Embury (ed.): High Temperature Oxidation and Sulphidation Processes, Pergamon Press(1990).

[18] R.A. Rapp (ed.): High Temperature Corrosion, National Association of Corrosion engineers

(1983).

[19] R. Streiff, J. Stringer, R.C. Krutenat and M. Caillet (ed.): High Temperature Corrosion -

Advanced Materials and Coatings ElsevierScience Publishers (1989).

[20] R.C. John: Proceedings of the Second International Conference of Heat Resistant Materials,

ASM-NACE, Gatlinburg, TN, 11-14, September 1995.

[21] R.C. John: NACE-Corrosion 96, paper 171, 1996.

[22] P. Waldner and. Pelton: Thermodynamic Modeling of the Fe-S System, in press.

[23] P. Waldner and A.D. Pelton/ Thermodynamic Modeling of the Ni-S System, in press.

[24] P. Waldner and A.D. Pelton/ Thermodynamic Modeling of the Fe-Ni-S System, in press.


24291 predicting equip lifetime - high t corr

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