Astm stp 1194 1994

S T P 1194 Application of Accelerated Corrosion Tests to Service Life Prediction of Materials Gustavo Cragnolino and Narasi Sridhar, editors ASTM Publication Code Number (PCN) 04-011940-27 481 ASTM 1916 Race Street Philadelphia, PA 19103 L i b r a r y of C o n g r e s s Cataloging-in-Publication Data A p p l i c a t i o n of a c c e l e r a t e d c o r r o s i o n t e s t s t o s e r v i c e l i f e p r e d i c t i o n of m a t e r i a l s / G u s t a v o C r a g n o l i n o a n d N a r a s i S r i d h a r , e d i t o r (STP ; 1194) " T h e A S T M S y m p o s i u m o n A p p l i c a t i o n of A c c e l e r a t e d C o r r o s i o n Tests t o S e r v i c e L i f e P r e d i c t i o n of M a t e r i a l s w a s h e l d d u r i n g - N o v , 1992 in M i a m i , F l a s p o n s o r e d b y A S T M C o m m i t t e e G - I o n C o r r o s i o n of M e t a l s F o r e w o r d " A S T M p u b l i c a t i o n c o d e n u m b e r (PCN) - 1 - I n c l u d e s b i b l i o g r a p h i c a l r e f e r e n c e s a n d index ISBN - - - i C o r r o s i o n a n d a n t i - c o r r o s i v e s - - T e s t i n g - - C o n g r e s s e s A c c e l e r a t e d l i f e t e s t i n g - - C o n g r e s s e s S t r e s s c o r r o s i o n -Testing Congresses I C r a g n o l i n o , G u s t a v o , II S r i d h a r , N a r a s i , III A S T M C o m m i t t e e G - I o n C o r r o s i o n of Metals IV A S T M S y m p o s i u m o n A p p l i c a t i o n of A c c e l e r a t e d C o r r o s i o n T e s t s t o S e r v i c e L i f e P r e d i c t i o n of M a t e r i a l s (1992 : M i a m i , F l a ) V S e r i e s : A S T M s p e c i a l t e c h n i c a l p u b l i c a t i o n ; 1194 TA418.74.A67 1994 620.i'1223 dc20 93-47376 CIP Copyright 1994 A M E R I C A N SOCIETY F O R T E S T I N G A N D M A T E R I A L S , Philadelphia, PA All rights reserved This material may not be reproduced or copied, in whole or in part, in any printed, mechanical, electronic, film, or other distribution and storage media, without the written consent of the publisher Photocopy Rights Authorization to photocopy items for internal or personal use, or the internal or personal use of specific clients, is granted by the A M E R I C A N SOCIETY F O R TESTING A N D M A T E R I A L S for users registered with the Copyright Clearance Center (CCC) Transactional Reporting Service, provided that the base fee of $2.50 per copy, plus $0.50 per page is paid directly to CCC, 222 Rosewood Dr., Danvers, M A 01923; Phone: (508) 750-8400; Fax: (508) 750-4744 For those organizations that have been granted a photocopy license by CCC, a separate system of payment has been arranged The fee code for users of the Transactional Reporting Service is 0-8031-1853-8/94 $2.50 + 50 Peer Review Policy Each paper published in this volume was evaluated by three peer reviewers The authors addressed all of the reviewers' comments to the satisfaction of both the technical editor(s) and the ASTM Committee on Publications To make technical information available as quickly as possible, the peer-reviewed papers in this publication were printed "camera-ready" as submitted by the authors The quality of the papers in this publication reflects not only the obvious efforts of the authors and the technical editor(s), but also the work of these peer reviewers The ASTM Committee on Publications acknowledges with appreciation their dedication and contribution to time and effort on behalf of ASTM Printed in Ann Arbor, MI February 1994 Foreword The A S T M symposium on Application of Accelerated Corrosion Tests to Service Life Prediction of Materials was held during 16-17 Nov 1992 in Miami, FL It was sponsored by ASTM Committee G-1 on Corrosion of Metals Gustavo Cragnolino and Narasi Sridhar, both of the Center for Nuclear Waste Regulatory Analyses in the Southwest Research Institute served as symposium cochairmen and editors of this publication Contents O v e r v i e w - - G CRAGNOLINO AND N SRIDHAR vii LABORATORY AND FIELD DATA ANALYSIS TECHNIQUES Relationship Among Statistical Distributions, Accelerated Testing and Future Environments R W STAEHLE Life Prediction of Ammonia Storage Tanks Based on Laboratory Stress Corrosion Crack Data R NYBORG AND L LUNDE 27 Corrosion Prediction from Accelerated Tests in the Chemical Process Industries-D C SILVERMAN 42 Composite Modeling of Atmospheric Corrosion Penetration Data R H MCCUEN 65 AND P ALBRECHT Application of Service Examinations to Transuranic Waste Container Integrily at the H a n f o r d S i t e - - D R DUNCAN, D A BURBANK, JR., B C ANDERSON, AND J A DEMITER 103 LIFE PREDICTION TECHNIQUES IN VARIOUS APPLICATIONS High Level Nuclear Waste Management in the U S A - - E D VERINK, JR 115 The Development of an Experimental Data Base for the Lifetime Predictions of Titanium Nuclear Waste Containers B M IKEDA, M G BAILEY, M J QUINN, AND D W SHOESMITH 126 Deterministic Predictions of Corrosion Damage to High Level Nuclear Waste C a n i s t e r s - - D D MACDONALD, M URQUIDI-MACDONALD, AND J LOLCAMA 143 Approaches to Life Prediction for High-Level Nuclear Waste Containers in the Tuff R e p o s i t o r y - - J A BEAVERS, N G THOMPSON, AND C L DURR 165 Crack Growth Behavior of Candidate Waste Container Materials in Simulated Underground Water J Y PARK, W J SHACK, AND D R DIERCKS 188 Prediction of Localized Corrosion Using Modeling and Experimental Techniques-N SRIDHAR, G, A CRAGNOLINO, J C WALTON, AND D DUNN Corrosion Aspects of Copper in a Crystalline Bedrock Environment with Regard to Life Prediction of a Container in a Nuclear Waste Reposltory R SJOBLOM 204 224 Correlation of Autoclave Testing of Zircaloy-4 to In-Reactor Corrosion P e r f o r m a n c e - - R A PERKINS AND S-H SHANN 239 The Importance of Subtle Materials and Chemical Considerations in the Development of Accelerated Tests for Service Performance Predictions-G PALUMBO, A M BRENNENSTUHL, AND F S GONZALEZ 252 C o r r o s i o n Life Prediction of Oil and Gas P r o d u c t i o n Processing E q u i p m e n t - 268 J KOLTS AND E BUCK Values of C o r r o s i o n R a t e of Steel in C o n c r e t e to Predict Service Life of Concrete S t r u c t u r e s - - c ANDRADE AND M C ALONSO 282 EXPERIMENTAL TECHNIQUES A New Index for the Crevice Corrosion Resistance of Materials Y x u AND H W PICKERING Acceleration of Stress-Corrosion Cracking Test for High-Temperature, High-Purity Water Environments by Means of Artificial Crevice Application M AKASH1 299 313 Application of a Multipotential Test M e t h o d for Rapid Screening of Austenitic Stainless Steels in Process E n v i r o n m e n t s - - P A AALTONEN, P K POHJANNE, S J T.~HTINEN~ AND H E HA.NNINEN 325 Spot-Welded Specimen Maintained Above the Crevice-Repassivation Potential to Evaluate Stress Corrosion Cracking Susceptibility of Stainless Steels in NaCI S o l u t i o n s - - s TSUJIKAWA, T SHINOHARA, AND W LICHANG C o n s t a n t Extension Rate Testing and Predictions of In-Service Behavior: The Effect of Specimen D i m e n s i o n s - - M R LOUTHAN, JR.~ AND W C PORR, JR 340 355 Applications of Electrochemical Potentiokinetic Reactivation Test To On-Site M e a s u r e m e n t s on Stainless S t e e l s - - M VERNEAU, J CHARLES, AND F DUPOIRON 367 New Electrochemical Method to Evaluate Atmospheric Corrosion Resistance of Stainless S t e e l s - - I MUTO, E SATO, AND S ITO 382 Author Index 395 Subject Index 397 Overview The initial impetus for this symposium was the long-term (hundreds to thousands of years) performance requirements in the disposal of high-level nuclear wastes that have driven the development of various life-prediction approaches for waste containers Life prediction has also gained increasing importance in other applications due to aging facilities and infrastructure (for example, nuclear power plants, aircraft, concrete structures), heightened concerns regarding environmental impact (for example, hazardous waste disposal, oil and gas production, and transportation), and economic pressures that force systems to be used for extended periods of time without appropriate maintenance Life prediction in the context of this publication pertains essentially to structures or systems that are undergoing corrosive processes For systems subjected to purely mechanical failure processes such as fatigue and creep, life prediction techniques have advanced to a greater degree Accelerated laboratory corrosion tests, which in the past have focused on screening tests for materials ranking and selection and quality control tests for materials certification, also have to be re-evaluated for their usefulness to life prediction A major objective of this symposium was to provide a forum for discussing the approaches to life prediction used by various industries A second objective, especially relevant to the mission of ASTM, was to discuss the appropriateness of various accelerated corrosion tests to life-prediction The papers in this volume cover many industries, although some areas, such as nuclear waste disposal, are more heavily represented than others However, the goal of being able to compare life prediction versus actual performance is yet to be achieved in many of the industries represented in this volume The papers in this volume are classified into three sections: Laboratory and Field Analysis Techniques, Life Prediction Techniques in Various Applications, and Experimental Techniques Laboratory and Field Data Analysis Techniques All the papers in this section describe various ways in which laboratory or field data can be extrapolated to predict service life A systematic approach to design and life prediction, as described by Staehle, would entail a definition of environmental conditions, material conditions, and failure modes, all combined in a probabilistic framework Several examples from the literature for the definition of failure modes are provided in this paper One important aspect of this paper is the organization of experimental data in a potential-pH framework so that failure modes can be defined for a given material under a given set of environmental conditions While the examples cited in this paper use the potential-pH diagrams as the basis for failure mode definition, other methods such as the definition of corrosion potential as a function of time can also be used to define failure modes The latter approach is described in other papers in this volume (for example, Macdonald et al., Sridhar et al.) The use of Weibull statistics in defining the probability of failure by stress corrosion cracking is also illustrated by Staehle Finally, the approach to predicting the overall probability of failure by a combination of failure modes, each with its own probability distribution is discussed It must be noted that this approach can be combined with other methods of combining failure modes such as fault tree analysis This method also differs from some of the other performance techniques that rely on developing an overall probability of failure through Monte-Carlo techniques whereby individual probabilities of various failure modes are not calculated separately Nyborg and Lunde discuss an empirical crack-growth model along with a probabilistic assessment based on the uncertainties in the input parameters for the case of ammonia cracking of carbon steel storage tanks While this model carries many uncertainties regarding the extrapolation of short-term crack-growth data to long-term pre- vii viii SERVICE LIFE PREDICTION OF MATERIALS diction, the methodology illustrates the importance of early and periodic inspection in reducing failure probability It also illustrates the sensitivity of failure probability to various material and design parameters, such that corrective actions can be pursued more effectively The use of artificial neural network to synthesize both short-term laboratory data and longerterm field experience in similar environments to make expected service-life predictions in a rapid manner is discussed by Silverman This technique is combined with an expert system to provide qualitative guidelines regarding the applicability of a specific material in a given environment for which only short-term data can be generated McCuen and Albrecht discuss the use of various curve-fitting approaches in extrapolating atmospheric corrosion data collected for time periods ranging up to 23 years to predict end-of-service corrosion penetration at 75 years They suggest that a composite model that combines a power-law behavior of corrosion penetration at short-times with a linear behavior at long-times is the most robust of the curve-fitting schemes The uncertainties in predicted penetrations at 75 years due to the uncertainties in the assumed model are highlighted Duncan et al describe the use of empirically measured corrosion rates and Poisson distribution for failure to predict the cumulative probability of failure of transuranic waste drums stored at Hanford, These papers also highlight the need for greater mechanistic (or deterministic as some prefer to call it) understanding of the various corrosion processes since extrapolations performed on the basis of parametric or statistical fitting o f present data result in considerable variations in the predicted behavior, depending on the selection of the fitting method Life Prediction Techniques in Various Applications The importance of an engineered barrier system in high-level nuclear waste disposal, as well as the interdependency of the engineering design and environmental conditions, is highlighted by Verink The next six papers deal with various life-prediction techniques related to high-level waste disposal containers The approach used by Ikeda et al in predicting the performance of Ti containers involves the assumption that crevice corrosion initiation is inevitable under the Canadian vault conditions, but that propagation is limited by the availability of oxidants to the open surface Hence, as time progresses, a deceleration of crevice corrosion propagation and eventual repassivation is predicted to occur For the same repository and container design, Macdonald et al use a variety of approaches to predict long-term performance The mechanistic modeling of corrosion potential is of special importance because it can be used to determine the corrosion modes as a function of environmental factors Macdonald et al also calculate the upper bound in corrosion rate by assuming that rate of transport of oxygen or other radiolytic species determines the dissolution rate of Ti and show that the calculated corrosion rates are rather low These models are further useful because they indicate the areas in which expenditures of experimental effort will be most fruitful Beavers et al also emphasize the need for mechanistic modeling and suggest that corrosion allowance materials whose corrosion rate can be well-defined coupled to a multibarrier system be given greater consideration for high-level nuclear waste packages in the U.S program Park et al use fracture mechanics-based tests under a variety of loading conditions to measure stress corrosion crack growth rate of types 304L and 316L stainless steels and alloy 825 in repository groundwater environments concluding that no significant environmentally assisted crack growth was observed in these alloys The limited environmental conditions examined makes it difficult to use this negative finding for longterm prediction The approach suggested by Sridhar et al is essentially similar to that of Ikeda et al., albeit for a different class of materials, namely Ni-based alloys and stainless steels The long-term prediction is attempted by considering the evolution of corrosion potential and critical potentials (initiation and repassivation potentials) for localized corrosion A OVERVIEW ix crevice initiation model is presented and the use of repassivation potential as a bounding parameter for container performance assessment is examined The need for detailed mechanistic justification of crevice repassivation potential and the shortcomings of the current models are pointed out Sj6blom reviews a variety of scenarios to be considered for assessing the safety of copper containers in the Swedish high-level waste program The use and limitations of accelerated laboratory tests to predict service performance of nuclear reactor components are examined in the next two papers Perkins and Shann show that a higher temperature laboratory test of various types of zircaloy fuel cladding can be used to distinguish the performance of these claddings in service In contrast, Palumbo et al warn that certain well-known accelerated laboratory tests may not be able to distinguish subtle variations in alloy 400 samples from two different lots that however, result in significant differences in service performance The last two papers in this section cover two widely different industries The corrosion of oil and gas production components occurs under complex environmental and flow conditions The paper by Kolts and Buck reviews various empirical correlations between corrosion or erosion rates and environmental and flow parameters The corrosion and erosion of the infrastructure has become a topic of great concern both in the U.S and elsewhere A n d r a d e and Alonso review the factors affecting the service performance of reinforced concrete structures, although the example they cite is mainly related to low-level radioactive waste vaults or bunkers The importance of preventing or delaying the onset of active corrosion of steel is pointed out It is also noted that unreinforced concrete structures have lasted for many centuries Experimental Techniques A new index for crevice corrosion susceptibility, based on the concept of change from passive to active behavior due to IR potential drop is presented by Xu and Picketing The advantage of this technique, in addition to being consistent with some of the observed crevice corrosion phenomena, is the ease with which it can be modeled on a mechanistic basis A possible limitation may be its inapplicability to stainless steels and other highly passivating alloys The use of graphite fiber wool as a crevice forming device to accelerate stress corrosion cracking of type 304 stainless steel and alloy 600 is examined by Akashi The salient feature of this work is the use of exponential probability distribution in comparing the accelerated laboratory test to documented service life Aaltonen et al propose a multipotential test technique whereby a number of stress corrosion cracking specimens under a range of applied potentials can be exposed to a given environment simultaneously to determine critical potentials for stress corrosion cracking The results of this type of test can be used to evaluate some of the proposed methodologies in papers on life prediction mentioned previously Tsujikawa et al examine the use of spot welded specimen, which simulates both the effects of crevices and residual stresses for predicting stress corrosion cracking The important result from this paper is that the critical potential for stress corrosion cracking is the same as the repassivation potential for crevice corrosion This simplifies the task of performance assessment considerably because one critical potential can be used to evaluate several failure modes However, these results need further scrutiny From the mechanical aspect, Louthan and Porr suggest that specimen geometry has a significant effect on stress corrosion cracking susceptibility as measured in slow strain rate tests The use of electrochemical potentiokinetic reactivation (EPR) test method to characterize the extent of sensitization of some austenitic stainless steels has been relatively well-established Some semi-empirical models exist that use the E P R values to predict the susceptibility to stress X SERVICE LIFE PREDICTION OF MATERIALS corrosion cracking of certain nuclear reactor components The E P R technique is extended to the case of a duplex stainless steel by Verneau et al A novel method to evaluate atmospheric corrosion beneath a thin electrolyte layer under heat transfer conditions is presented by Muto et al The interesting feature of this paper is the comparison of accelerated laboratory test results using a rating number derived from Weibull distribution parameters to rating number from field exposure tests The applicability of this test technique to studying corrosion under repeated wet and dry cycles and to moist environments needs to be examined The need for long-term life prediction of components exposed to corrosive conditions necessitates a re-evaluation of many of the accelerated corrosion test methods that are being used at present As many of the papers in this volume suggest, the comparison between accelerated laboratory tests and service life data must be made in a statistical framework The evaluation of appropriate test methods will also be aided by the simultaneous development of predictive models It is hoped that the papers contained in this volume will stimulate further examination of the present-day corrosion test methods, many of which are contained in ASTM standards We wish to thank the authors for their efforts in the publication of this volume We also wish to thank the reviewers for their assistance in improving the quality of this publication, the ASTM staff and Mr Arturo Ramos for their timely assistance in organizing the symposium and assembling this publication Finally, we wish to thank Dr Michael Streicher and Mr Jefferey Kearns who provided the initial encouragement in organizing this symposium Gustavo Cragnolino Narasi Sridhar Center for Nuclear Waste Regulatory Analyses, Southwest Research Institute, San Antonio, TX; symposium cochairmen and editors MUTO ET AL ON A NEW ELECTROCHEMICAL METHOD 385 Accelerated test Rust staining of stainless steels in the atmosphere has three steps: (I) the formation of the water drop containing chloride ion and/or sulfur dioxide (S02) on the surface, (2) increased concentration of corrosive ions and diffusion of dissolved oxygen through drying process, (3) local b r e a k d o w n of passive film and subsequent dissolution of zeta/ The incubation time to locai b r e a k d o w n of passive film under a thin electrolyte environment corresponds to initiation of rust staining of stainless steels exposed to an atmospheric environment Fig.2 shows the schematic illustration of the newly developed accelerated test apparatus newly developed The apparatus was similar to that previously used [8], except for the use of a sheet heater, which accelerates the formation of a thin electrolyte layer The specimen was adhered on the sheet heater The cotton cloth, both sides of which were immersed in test solution reservoir, was placed on the specimen A thin electrolyte layer, simulating an actual atmospheric environment, was formed by the capillary p h e n o m e n a through the cotton cloth The incubation time to the b r e a k d o w n of passive film was monitored by the change of electrode potential with a saturated ca/omel electrode The chemical compositions of the stainless steels with No.2B surface finish used in this accelerated test were given in Table The specimens were covered with silicone rubber except the test area of 20mmXl3mm Synthetic seawater, corresponding to a marine environment, was employed as an electrolyte The surface temperature of specimens was kept at 333K b y the sheet heater Glass case Voltmeter I Specimen Recorder Cotton ctoth \ Thermocouple ~ ~ - -~ -2_ - Cell FIG Schematic illustration of accelerated corrosion test apparatus 386 SERVICELIFE PREDICTION OF MATERIALS TABLE - - C h e m i c a l c o m p o s i t i o n s accelerated test Specimen AISI T y p e / Tradename(Finish) llCr 17Cr 19Cr-lMo 19Cr-2Mo 18Cr-8Ni 17Cr-12Ni-2.5Ho 25Cr-13Ni-0.8Mo YUS409Da(2B) 430 (2B) (2B) YUS190 a (2B) 304 (2B) 316 (2B) YUS170 a (2B) (mass%) of stainless C Mn Cr 0.013 0.058 0.012 0.011 0.069 0.072 0.019 0.35 0.13 0.14 0.15 0.15 0.70 0.43 steels for the Ni 10.74 16.01 19.28 19.02 18.29 17.62 24.68 Mo Other 0.06 Ti:0.34 0.10 AI:0.10 0.29 0.98 Cu:0.37 Mo:l.81 Nb:O.29 Ti:0.18 8.74 11.30 2.19 Cu!0.29 12.78 0.73 N:0.35 aTradename of Nippon Steel Corporation TABLE - - R a t i n g n u m b e r environment Specimen of specimens AISI T y p e / Tradename(Finish) 16Cr-9Mn-2Ni 18Cr-6Ni 17Cr-7Ni 18Cr-8Ni 18Cr-SNi 17Cr-12Ni-2.5Mo 18Cr-7Ni-2Cu-1Ho 25Cr-13Ni-0.8Mo 10.9Cr 11Cr 12Cr 13Cr 16.5Cr 17Cr 19Cr-2Ho YUSI20 a (2D) YUS27A a (2B) 301 (2B) 304 (2D) 304 (2B) 316 (2B) YUS316ca(2B) YUS170 a (2B) 409 (2D) YUS409Da(2B) YUS410wa(2B) 410 (2B) YUS430Da(2B) 430 (2B) YUS190 a (2B) aTradename of Nippon Steel Results Exposure and exposed to the Rating marine number 10 5 5 5 2 4 2 2 3 0 2 2 2 0 0 2 1 1 2 0 0 (year) Corporation Discussion test Table shows the results of the long term exposure test in the marine environment In order to know the relationship between the rating n u m b e r of i n i t i a l r u s t s t a i n i n g a n d a l l o y c o m p o s i t i o n s , t h e r a t i n g MUTO ET AL ON A NEW ELECTROCHEMICAL METHOD 387 n u m b e r s of t h e s p e c i m e n s a f t e r y e a r w e r e e x a m i n e d v i s u a l l y The d e p e n d e n c e of t h e r a t i n g n u m b e r on t h e a l l o y c o m p o s i t i o n w a s a n a l y z e d b y m u l t i - r e g r e s s i o n m e t h o d a s s h o w n in Fig.3 T h e r a t i n g n u m b e r of s t a i n less steels exposed for year, Rlyear, was given by the following equation: Rlyear=0.36Xl-l.64 (1) w h e r e X is t h e a l l o y i n d e x , o r t h e a t m o s p h e r i c c o r r o s i o n r e s i s t a n c e i n d e x d e p e n d i n g o n t h e a l l o y c o n t e n t s d e r i v e d from m u l t i - r e g r e s s i o n a n a l y s i s T h i s i n d e x w a s w r i t t e n a s follows: Xl=[Cr]-0.08[Ni]+l.05[Mo]=[Cr]+ [Ho] (2) Here [Cr], [Nil, a n d [Mo] i n d i c a t e alloy c o n t e n t in mass% of chromium, n i c k e l , a n d m o l y b d e n u m r e s p e c t i v e l y I n E q u a t i o n (2), t h e c o e f f i c i e n t of n i c k e l c o n t e n t is a l m o s t zero This alloy i n d e x a f t e r y e a r in t h e m a r i n e e n v i r o n m e n t c a n b e e x p r e s s e d a s Xl=[Cr]+[Mo] This r e s u l t s u g g e s t s t h a t n i c k e l h a s no i n f l u e n c e on t h e r e s i s t a n c e t o i n i t i a l r u s t s t a i n i n g of s t a i n l e s s s t e e l s T h i s a l l o y i n d e x Xl=[Cr]+[Mo] is a l s o s i m i l a r to t h e p i t t i n g i n d e x ([Cr]+3.3[Mo]) t h a t was d e r i v e d from t h e r e l a t i o n s h i p b e t w e e n a l l o y c o m p o s i t i o n s a n d p i t t i n g p o t e n t i a l in a c h l o r i d e s o l u t i o n [9] O o O~ T Marine atmosphere (Akocity.lyearexposure)y * " / J , O~ c" e0 cr R=0.36N-1.64 x,= tc l-o.os NiJ- osr MoJ 1'0 i; 2'o s 30 x, FIG - - Effect of alloy compositions on the rating number after l year in the marine environment The c h a n g e of r a t i n g n u m b e r w i t h time of f o u r d i f f e r e n t g r a d e s of s t a i n l e s s s t e e l s is s h o w n in Fig.4 T h e s e r e s u l t s s u g g e s t t h a t most of s t a i n l e s s s t e e l s e x p e r i e n c e d s e v e r e c o r r o s i o n w i t h i n t h e f i r s t two y e a r s in t h i s e n v i r o n m e n t (Fig.4(a)) F i g ( b ) a l s o s h o w s t h e same t e n d e n c y of t h e c h a n g e in t h e r a t i n g n u m b e r w i t h t h e s q u a r e of t h e i n v e r s e time The c h a n g e in r a t i n g n u m b e r , AR, w a s e x p r e s s e d a s follows: 388 SERVICELIFE PREDICTIONOF MATERIALS AR=4tl-2-4 (3) Here t I is exposure time in year Combination of the Equation (I) and (3) leads to the following equation, which gives the relation between the rating number, R, after several years and exposure time R:Rlyear+AR (4) =(0.36Xl-l.S4)+(4tl-2-4) (5) Here X is the atmospheric corrosion resistance index as indicated in Equation (2) According to Equation (5), the resistance to initial rust staining resistance of stainless steels was related to chromium and m o l y b d e n u m contents, but the change in rating n u m b e r was directly related t o e x p o s u r e time Marine atmosphere I (Ako city ) $6 t l / year I12i t I I 10 i ~ , 19Cr-2Mo "'~-.~ "" z, ~ ~ 18Cr-TNi-2Cu-lMo ~3 ~3 ""b "'2 I ''~ Accelerated "- R=a.f~2,b 2'5 16o I0%f~2/year-' t/year (a) FIG 1~ ~,, (a=4~) (b) A t m o s p h e r i c c o r r o s i o n b e h a v i o r of d i f f e r e n t g r a d e s of s t a i n less s t e e l s The d e p e n d e n c e of t h e r a t i n g n u m b e r o n (a) e x p o s u r e time a n d (b) t h e s q u a r e if t h e i n v e r s e time corrosion test The atmospheric corrosion r e s i s t a n c e index for stainless steels c a n b e also d e r i v e d from t h e n e w l y d e v e l o p e d a c c e l e r a t e d t e s t Fig.5 shows the corrosion potential oscillations for stainless steels u n d e r t h e t h i n e l e c t r o l y t e l a y e r of t h e a c c e l e r a t e d t e s t , w h i c h s i m u l a t e s t h e a c t u a l a t m o s p h e r i c c o n d i t i o n s (Fig.2) One oscillation c o r r e s p o n d s to local b r e a k d o w n of p a s s i v e film a n d r e p a s s i v a t i o n p r o c e s s All t h e s p e c i m e n s e x p e r i e n c e d p o t e n t i a l o s c i l l a t i o n s a n d f i n a l l y had t h e l e s s n o b l e p o t e n t i a l a r o u n d -0.4V, w h i c h i n d i c a t e s t h e f o r m a t i o n of a n i r r e - MUTO ET AL ON A NEW ELECTROCHEMICAL METHOD 389 versible macro pit on the surface The similar pits were observed on the exposed specimens to the marine atmosphere Therefore, the incubation time to pit initiation was employed as evaluation parameter for quantitative rust staining resistance of stainless steels in the marine environment 0.4 02 uJ u 19Cr-2Mo / u3 ~4 > -02 \ 144 -0.4 / " 17Cr 19Cr-lMo -0.6 i ~ , i , , -0"80 , ~ , 12 t2/ FIG i I 1 1 20 24 28 ks Potential-time curves for stainless steels obtained in the accelerated test , , , o, j / / , ~30 , , , , 2.2 , , , , , , , - o - 11Cr .- l?Cr 19Cr-1Mo 19Cr-2Mo I ] 100 I I l I I I I I I I I I I I I I 10' t2/ ks FIG Neibull distributions of the incubation time to pit initiation 102 32 390 TABLE SERVICELIFE PREDICTION OF MATERIALS Parameters of the Weibull distributions of the incubation time to pit initiation in the thin electrolyte layer Specimen llCr 17Cr 19Cr-iMo 19Cr-2Mo 18Cr-8Ni 17Cr-12Ni-2.5Mo 25Cr-13Ni-0.SMo Shape parameter, m 4.3 2.2 2.2 2.2 3.6 2.1 2.5 Mean value, ~ (ks) 4.50 6.78 13.80 16.26 4.92 9.72 24.12 The Weibull distribution was applied to determine t h e mean value of the incubation time, because t h e pit nucleation process is a statistic phenomenon [i0] Fig.6 shows t h e plot of t h e Weibull distributions of t h e incubation time to pit initiation under the t h i n electrolyte layer These data follow straight lines, meaning t h a t the incubation time to pit initiation obeys the Weibull distribution These distributions indicate t h a t t h e statistical evaluation of t h e time to pit initiation is useful to compare the corrosion resistance between t h e specimens due to overlapping of the distributions The parameters of these distributions are given in Table The slope of t h e s t r a i g h t line corresponds to t h e shape parameter, and t h e s e values listed in Table are in t h e range of 2.1 to 4.3 This result suggests t h a t t h e shapes of t h e distributions are almost the same Therefore, t h e relative r e s i s t ance to pit initiation under the t h i n electrolyte layer can be evaluated from the mean value of the distributions Then, t h e mean value of the Weibull distribution, #, is employed for the representative The relationship between t h e Weibull mean value, /4 of t h e incubation time and the chemical composition was determined by multi-regression analysis similar to t h a t used for determination of Equation (1) The mean value, #(ks), was given by the following equation: =1.58X2-16.70 (6) w h e r e X is the alloy index obtained b y this accelerated test The index X is defined by Equation (7) X2=[Cr]-0.18 [Ni]+0.88[Mo]=[Cr]+[Mo] (7) Fig.7 shows the relationship between X obtained b y multi-regression analysis and the m e a n value, ~, of the incubation time to pit initiation The m e a n value, ~, has a linear relation with X value, and this alloy index is almost the same as that obtained from % h e exposure test in Equation (2) x2=x I (=[Cr]+[Mo]) (8) MUTO ET AL ON A NEW ELECTROCHEMICAL METHOD 391 30 /J =1.58X2-16.70 X2 = [Cr] - 0.18[Ni] + 0.88[ Mo] 24 @ 18 12 " 05 I I I I 10 15 20 25 30 X2 FIG E f f e c t of alloy c o m p o s i t i o n s on t h e mean v a l u e of t h e i n c u b a t i o n time t o p i t t i n g in t h e a c c e l e r a t e d t e s t This result suggests that the accelerated test conditions approximately simulate the actual atmospheric environment, and the quantitative atmospheric corrosion resistance can be estimated from the mean value, /I, of the incubation time The difference in the mean value, //, indicates the quantitative difference in rust staining resistance of specimens Furthermore, when X2=X is substituted in Equation (6), the following equations are derwed //=i 58X2-16.70=I.58XI-16.70 Xl=fZ/l.58+10.6 (9) (lO) Substituting the equation (i0) for X in the equation (5) yields the following equation, which gives the rating number, R, after several years in the marine environment R= (/z/4.39+2.18)+ ( t - - ) (11) H e r e t is e x p o s u r e time in y e a r s , a n d /z (ks) is t h e mean v a l u e of t h e i n c u b a t i o n time to p i t t i n g in t h e a c c e l e r a t e d t e s t Th e r a t i n g n u m b e r e s t i m a t e d b y t h i s a c c e l e r a t e d t e s t is m o r e a c c u r a t e t h a n t h a t c a l c u l a t e d f r o m t h e a l lo y i n d e x Xl=[Cr]+[Mo ] b y u s i n g 392 SERVICELIFEPREDICTIONOF MATERIALS Equation (5), because this newly developed test also evaluates the influence of other alloy elements, inclusions, and surface finish on rust staining of specimens Fig.8 shows the relationship between the rating n u m b e r of specim e n s exposed to the marine environment and that estimated by Equation (ii), suggesting that the rating n u m b e r and rust staining resistance of stainless steels in the marine environment can be evaluated by this newly developed test v l ~5 / 2years o 10years 04 o3 o_ "'2 o o o c n~ Rating(Accelerated t e s t-9 )(good) FIG Relationship between the rating n u m b e r of the specimens exposed to the marine environment and that estimated in the accelerated test CONCLUSIONS the The rating number of rust staining of stainless marine environment was expressed as follows: steels exposed to R=(0.36XI-I.64)+ (4t-2-4) Xl=[Cr]+[Mo] w h e r e X is the alloy index that indicates the relative corrosion resistance to rust staining, t is exposure time in years The rating n u m b e r of rust staining of stainless steels was also evaluated in the accelerated test and was expressed as follows: R= (~/4.39+2.18)+(4t-2-4) w h e r e ~ (ks) is the m e a n value of the incubation time to pitting in the accelerated test, t is exposure time in years MUTO ET AL, ON A NEW ELECTROCHEMICAL METHOD 393 Good correlation was observed between the rating numbers of specins in the exposure test and that estimated in the accelerated corro,n test FERENCES Black, H L and Lherbier, L W., "A Statistical Evaluation of Atmospheric, In-Service, and Accelerated Corrosion of Stainless Steel Automotive Trim Material," Metal Corrosion in the Atmosphere, ASTM STP 435, American Society for Testing and Materials, Philadelphia, 1968, pp.3-32 Karlson, A and Olsson, J., "Atmospheric Corrosion of Stainless Steels," 7th Scandinavian Corrosion Congress, 1975, pp.71-86 Needham, N G., Freeman, P F., Wilkinson, J., and Chapman, J., "Atmospheric Corrosion Resistance of Stainless Steels," Stainless Steels '87, The Institute of Metals, York, 1988, pp.215-223 Kearns, J R., Johnson, M J., and Pavlik, P J., "The Corrosion of Stainless Steels in the Atmosphere," Degradation of Metals in the Atmosphere, A S T M STP 965, American Society for Testing and Materials, Philadelphia, 1988, pp.35-51 Baker, E A and Lee, T S., "Long-Term Atmospheric Corrosion Behavior of Various Grades of Stainless Steel," Degradation of Metals in the Atmosphere, A S T M STP 965, American Society for Testing and Materials, Philadelphia, 1988, pp.35-51 Bates, J F and Phelps, E H., "An Appraisal of Evaluation Tests for Stainless Steel Automotive Trim," Advances in the Technology of Stainless Steels and Related Alloys, A S T M STP 369, American Society for Testing and Materials, Philadelphia, 1963, pp.200-208 Bush, G F., Garwood, W J., and Tiffany, B E., "Accelerated Tests As a Method of Predicting Service Corrosion of Exterior Automotive Trim," Advances in the Technology of Stainless Steels and Related Alloys, A S T M STP 369, American Society for Testing and Materials, Philadelphia, 1963, pp.209-222 Ito, S., Yabumoto, M., Omata, H., and Murata, T., "Atmospheric Corrosion of Stainless Steels," Passivity of Metals and Semiconductors, Elsevier Science Publishers B.V., Amsterdam, 1983, pp.637-642 Speidel, M 0., "Corrosion Science of Stainless Steels, " Proceedings of International Conference on Stainless Steels (Stainless Steels '91), Iron and Steel Institute of Japan, 1991, pp.25-35 Shibata, T., "Evaluation of Corrosion Failure by Extreme Value Statistics," !SIJ International, Vol 31, No 2, 1991, pp.l15-121 STP1194-EB/Feb 1994 Author Index L A Aaltonen, P A., 325 Akashi, M., 313 Albrecht, P., 65 Alonso, M C., 282 Anderson, B C., 103 Andrade, C., 282 Lichang, W., 340 Lolcama, J., 143 Louthan, M R., Jr., 355 Lunde, L., 27 M Macdonald, D D., 143 McCuen, R H., 65 Muto, I., 382 B Bailey, M G., 126 Beavers, J A., 165 Brennenstuhl, A M., 252 Buck, E., 268 Burbank, D A., Jr., 103 N Nyborg, R., 27 C P Charles, J., 367 Cragnolino, G A., 204 Palumbo, G., 252 Park, J Y., 188 Perkins, R A., 239 Pickering, H W., 299 Pohjanne, P K., 325 Porr, W C., Jr., 355 D Demiter, J A., 103 Diercks, D R., 188 Duncan, D R., 103 Dunn, D., 204 Dupoiron, F., 367 Durr, C L., 165 Q Quinn, M J., 126 S G Sato, E., 382 Shack, W J., 188 Shann, S.-H., 239 Shinohara, T., 340 Shoesmith, D W., 126 Silverman, D C., 42 Sjo(omlaut over first o)blom, R., 224 Sridhar, N., 204 Staehle, R W., Gonzalez, F S., 252 H Hfinninen, H E., 325 Ikeda, B M., 126 Ito, S., 382 T Tahtinen (omblaut on a), S J., 325 Thompson, N G., 165 Tsujikawa, S., 340 K Kolts, J., 268 395 Copyright e 1994 by ASTM Intemational www.astm.org 396 SERVICE LIFE PREDICTION OF MATERIALS U Urquidi-Macdonald, M., 143 W Walton, J C., 204 V X Verink, E D., Jr., 115 Verneau, M., 367 Xu, Y., 299 STP1194-EB/Feb 1994 Subject Index Crystallographic orientation, 252 A Acidification, 299 Ammonia, 27 Autoclave testing, 239 D Damage accumulation, 165 Deformation, residual, 252 Degradation rate, 103, 355 Distribution parameters, B Barriers multiple, design, 165 natural, 115 Bedrock environment, 224 Brass, free machining, 355 E C Carbon dioxide, 268 Carbon steel, 27 Chemical process industries, 42 Chloride, 204, 299 sodium, 340 Chromium, 367 Cladding, 239 Coincidence site lattice, 252 Concrete service life, 282 Constant extension rate testing, 355 Containers, nuclear waste, 188 damage prediction, 143 lifetime prediction, 126, 165, 224 multi-purpose, 115 transuramc, 103 Copper, 224 Cracking fatigue, growth, 188 hydrogen-induced, 126 stress corrosion, 27, 188, 313, 325, 340 Crevice, artificial, 313 Crevice corrosion susceptibility, 299 Crevice depassivation, 204 Crevice repassivation, 126, 204, 340 397 Electrochemical methods, 382 Electrochemical Potentiokinetic Reactivation, 367 impedance spectroscopy, 42 potential range, 325 Electrode, rotating cylinder, 42 Embrittlement, mercury, 355 Engineered barrier system, 115 Environmental definition, F Fatigue, corrosion, 188 Field simulations, 252 Fracture, unstable, 355 G Galvanic coupling technique, 126 Gas facility, 268 Graphite-fiber wool, 313 H Hydrology, 115 Hydrolysis, 204 Immersion tests, 42 Impurity segregation, 252 Intergranular corrosion, 367 Ion mass spectrometry, secondary, 252 398 SERVICE LIFE PREDICTION OF MATERIALS L Lifetime distribution, 313 Linear model, 65 M Marine atmosphere, 382 Materials definition, Materials selection, 165, 268 Mercury embrittlement, 355 Metamorphic rocks, 224 Microstructure, 252 Mixed Potential Model, 143 Mode and submode definition, Modeling composite, 65 crack growth, 27 crevice, 204 deterministic, 143 exponential distribution, 313 linear, 65 mechanistic, 165 mixed potential, 143 quantitative, 299 Multipotential test, 325 Precipitations, intermetallic phase, 367 Probabilistic methods, 27 Propagation phenomenon, 165 Q Quantitative method, 299 R Radiolysis products, 143 Rate testing, constant extension, 355 Rating number, 382 Reactors boiling water, 313, 325 pressurized water, 239 Rebars, 282 Repassivation, 126, 204, 340 Residual deformation, 252 Rust staining, 382 N Neural networks, artificial, 42 Nickel-base alloy, 313 Nuclear waste management, 188, 224 damage prediction, 143 high level, 115 low level, 282 storage life prediction, 126, 165 O Oil facility, 268 Oxygen diffusion rate, 282 P Penetration data, corrosion, 65 Pitting, 299 Plutonic rock repositories, 143 Polarization scans, 42 Power model, 65 Screening, rapid, 325 Segregation, trace impurity, 252 Sensitization, 367 Service examinations, 103 Site lattice, coincidence, 252 Slow strain rate testing, 355 Sodium chloride, 340 Soil exposure, 103 Staining, rust, 382 Statistical distribution, 3, 65 Statistical methods, 115 Steam autoclave test, 239 Steel, 65, 103, 282 carbon, 27 stainless, 188, 204, 313, 325, 367 austenitic, 340 rust staining on, 382 Storage environment, 103 Stress corrosion cracking, 27, 188, 313, 325, 340 Sulfate, 204 INDEX 399 T Tanks, storage ammoma, 27 nuclear waste, 103, 188 damage prediction, 143 lifetime prediction, 126, 165, 224 multi-purpose, 115 waste container integrity, 103 Tarps, plastic, 103 Tearing modulus, 355 Titanium alloy, 143 Grade-2, 126 Grade-12, 126 Thermal loading, 115 Tuff Repository, 165 W Waste, nuclear, 224 high level, 115, 143, 165, 188 low level, 282 Weibull, Welds, spot, 340 Y Yucca Mountain, 115, 188 Z V Velocity, 268 Zircaloy-4, 239 ISBN: 0-8031-1853-8