ML18040A330

Rev 0 to Technical Rept 97181-TR-03, EPR Testing of Boat Samples from Core Shroud Vertical Welds V-9 & V-10 at NMP Unit 1.

ML18040A330
Person / Time
Site:	Nine Mile Point
Issue date:	02/28/1998
From:	Rich Smith, David Williams ALTRAN CORP.
To:
Shared Package
ML17059B904	List: ML17059B903 ML17059B905 ML17059B906 ML17059B907 ML18040A330
References
97181-TR-03, 97181-TR-03-R00, 97181-TR-3, 97181-TR-3-R, NUDOCS 9803090216
Download: ML18040A330 (85)

Text

EPR Testing of Boat Samples from Core Shroud Vertical Welds V-9 and V-10 at NMP-1 Technical Report No. 971S1-TR-03 Revision 0 Volume 1 of 1 prepared for:

Niagara Mohawk Power Corporation Nine Mile Point Unit 1 February 1998 98030902ib 980227 II PDR ADQCK 05000220 P PDR I

I Report Record Document No.: Rev. No.: 0 Sheet No.:~

Nuclear Safety Related Yes No ~ Total No. of Sheets ~4 TITLE: e tin of o t am le from. ore hroud Vertical Weld. V-and V- a P-1 CLIENT: Nia ar hawk FACILITY: NMP - n t 1 REV. DESCRIPTION: Revisi n - ri inal I e COMPUTER RUNS (identified on Computer File Index):

Error reports evaluated by: Date:

Impacted by error reports: No Yes (if yes, attach explanation)

Ori inat r(s} Date Checker(s) Date a/~/jp R.E. Smith 2/20/9S DESIGN VERIFICATION: (EOP 3.4) Required Not Required"

" Justification Non " A" Performed by: Date:

Method of design verification:

Design Review Alternate Calculations Qualification Test (Attached) (Data/Results Attd.i Comments resolved by: Date:

Design verifier concurrence: Date:

APPROVED FOR RELEASE PROJECT MANAGER: Date: e ~~ ~g ENGINEERING MANAGER:

R.E. Smith

~~

D.S. Williams Date:

I

I Altran Corporation Technical Report TR 97181-TR-03 Revision 0 EPR Testing of Boat Samples from Core Shroud Vertical Welds V-9 and V-10 at NMP-1

1. Introdnction to EPR Testing A method of measuring the susceptibility of a material to intergranular stress corrosion cracking (IGSCC) was proposed in the mid-1970s and is known as Electrochemical Potentiokinetic Reactivation (EPR) testing. The method uses the potentiodynamic reactivation response of electrochemically passivated stainless steel and measures the electrochemical activity of grain boundaries. The susceptibility of austenitic stainless steels, and other austenitic materials

'ncluding nickel-based materials, is produced by the precipitation of chromium carbides at the grain boundaries of these materials. The precipitation of chromium-rich carbides at the grain boundaries depletes the chromium content of the matrix material immediately adjacent to the precipitates. This phenomenon is known as grain boundary sensitization. Sensitization renders the material susceptible to IGSCC in a supporting environment. The electrochemical response at these locations will increase as the degree of sensitization increases. The reactivation technique was developed as a'quantitative measure of the degree of sensitization in types 304 and 304L stainless piping. It was initially developed to screen stainless steel recirculation piping and welding processes used in boiling water reactor (BWR) power plants.

The EPR technique uses several testing methods in order to minimize the scatter in results due to testing variables such as surface roughness and grain size. These methods include the single-scan technique, the double-loop technique, and a field version of the double-loop technique. The first two techniques are methods suited to laboratory settings, and the field double-loop method was designed for direct component applications. All methods consist of first establishing the corrosion potential E~ of the specimen in the test solution 0.50 molar H,SO4 + 0.01 molar KSCN. The specimen surface is prepared by polishing the surface to a 1 micron finish using diamond paste. The test surface is polarized at a potential of +200 mv [saturated calomel electrode (SCE)] for a period of 2 minutes. After polarization is established, the potential is decreased to its open circuit value, E~ at a constant rate of 6 V/hr (1.67 mV/sec). This reactivation leads to the preferential breakdown of the passive film on the sensitized material where there is chromium depletion. As a result a large loop is generated in the curve of the potential versus current. The area under this loop is proportional to the electric charge, Q, where Q depends on the surface area and the grain size. On nonsensitized material the passive film remains essentially intact, and the size of the loop, and therefore, Q, are small. The charge often is normalized (adjusted) to the total grain boundary area. This produces a quantitative measure of the degree of sensitization. The adjusted charge is then divided by the test surface area and is expressed in terms of charge per unit area.

Page 3

I I

I I

I I

I

Altran Corporation Technical Report TR 97181-TR-03 Revision 0 The double-loop techniques are conducted in a similar fashion, except the anodic scan is followed by a cathodic (reverse) scan. The ratio of the maximum current attained in the reverse scan divided by the maximum current attained in the anodic scan is used as a measure of the degree of sensitization. This method is reported to work with rougher surfaces produced using 100 grit silicon carbide polishing papers (140 micron). Typically finer papers are used such as 600 grit. Technical workers at Ishikawajima Heavy Industries (IHI) established this method as a preferred test method in Japan. It has been suggested that the ratio IR/IA should be relatively insensitive to test variables grain size and surface roughness (see Appendix 3). The grain size influences the surface area of the material activated in the test. The electrochemical response should be similar for both anodic and reverse scans. An increased degree of surface roughness increases the surface area being tested. However, the increased area should produce a similar electrochemical result regardless of which direction is scanned. Since the method ratios the two maximum currents, there should be no net effect from either variable grain sizes or differing degrees of surface roughness assuming similar responses from both scanning directions. Majidi and Streicher reported that the grain size response is dependent upon scanning direction, and therefore a grain boundary correction is required to achieve self-consistent results (Reference 1).

2. Boat Sample Descriptions The degree of sensitization of a material influences IGSCC, and is one input parameter used to predict crack growth rates using the General Electric PLEDGE code (Reference 9). A quantitative measurement of the degree of sensitization associated with the core shroud vertical welds was needed to confirm the material conditions that had been assumed to estimate crack growth rates using the PLEDGE model. These predicted crack growth rates were used to estimate the progression of identified cracks in the V-9 and V-10 vertical core shroud welds at NMP-1 for the duration between restart and the next planned outage. Crack disposition has been detailed in the crack evaluation and the safety analysis reports submitted to the Nuclear Regulatory Commission (References 4 and 5). These reports assumed a moderately sensitized material condition. Austenitic stainless steel material that is moderately sensitized should yield EPR test results between 2 and 15 coulombs/cm in the single loop test. EPR testing was undertaken to confirm these assumptions.

Two boat samples were removed from the NMP-1 core shroud to validate the cracked conditions identified by inspection, and to determine the nature and potential causes of cracking. These samples were taken from the material adjacent to the vertical seams forming the core shroud mid-cylinder. Weld V-10 and weld V-9 identify the vertical welds that join two roll-formed type 304 austenitic stainless steel plates, li/~ inches thick. The first sample, identified as V-10, was removed from the heat-affected zone of weld V-10 on the outside of the shroud. Sample V-i0 was removed from the right side of weld V-i0 at a vertical position approximately 57.5 inches below the upper horizontal weld joining this mid-cylinder to the upper cylinder. The horizontal weld was identified as H-4. Sample V-10 contained a portion of the crack identified with vertical weld V-10.

Page 4

Altran Corporation Technical Report TR 97181-TR-03 Revision 0 Sample V-9 was removed from the heat affected zone of Weld V-9 on the inside surface. The sampling location was approximately 25 inches below horizontal weld H-4. This sample contained no crack. The V-9 sample material had been exposed to a greater neutron fluence than the V-10 sample material. Fluence is a variable known to influence the degree of sensitization as the fluence level increases. No evidence of irradiation assisted stress corrosion (IASCC) was identified in either of the boat samples (Reference 3). However, it was important to explore the possibility that the degree of sensitization may have been enhanced and the resulting crack

'rowth rate increased. The fluence of both boat samples was measured (References 2 and 10).

The mid-wall fluence of boat sample V-10 measured 1.54 x 10 '/cm, and the surface fluence of boat sample V-9 (fluence at inner surface of core shroud) measured 3.088 x 10" n/cm'.

3. DOS Evalnation based on Optical Metallography The optical microstructures were carefully examined for both samples. These evaluations indicated that the degree of sensitization in sample V-10 was slightly greater than the degree of sensitization in sample V-9. The weld heat affected zone (HAZ) microstructure in sample V-10 was clearly delineated; however, the HAZ for weld V-9 was less defined, although evidence of grain boundary carbide precipitation was apparent in both samples. Both microstructures were judged moderately sensitized. These qualitative estimates are consistent with the moderate sensitization assumptions used in the PLEDGE model to estimate crack growth rates. No evidence of neutron induced sensitization could be determined from the optical metallography.

Therefore a quantitative test was needed to provide an indication of the degree of sensitization.

EPR testing was performed on a representative cross-section prepared &om each boat sample.

4. EPR Test Resnlts and Discussion The laboratory facilities at McDermott Technologies were not equipped to perform the laboratory EPR testing techniques, because the radiation levels of the samples were high.

Therefore, the double-loop field procedure was selected and equipment obtained to perform the test. It was recognized that a correlation of the double-loop field test results with results from single scan tests would be needed to provide direct comparisons with DOS parameters assumed in the PLEDGE modeling of these crack growth rates. The IHI Field DOS Tester equipment was selected (Appendix 3) and setup in the radiation controlled examination facility at the McDermott Technologies (MDT) laboratory. The IHI equipment was furnished with Type 304 stainless steel standards that represented both a low degree of sensitization (Sample S, engraved 0.008) and a high degree of sensitization (Sample F, engraved 0.434). The test equipment was applied to the standards to validate the calibration. Values averaging 0.007 Ii,/Iwere obtained for, Sample S, and values averaging 0.373 Ii,/Iwere obtained for Sample F (Reference 7). These values were considered acceptable and the methods were validated.

The double-loop testing method does not provide direct output of charge per unit surface area.

Therefore, the same standard specimens were transported to GE Corporate R 2 D for comparative testing with laboratory devices capable of both the single loop and the double-loop Page 5

I I

I

Altran Corporation Technical Report TR 97181-TR-03 Revision 0 procedures. These results produced a method with which to calibrate the double-loop field results to the single loop results. Therefore charge/unit area could be established to interpret the double-loop field results measured on the radioactive samples (Reference 8).

Double-loop test results at MTI using the IHI Type S-61 DOS testing equipment are reported in Appendix 1 (Reference 7) for field test Standards F and S, a sample having a median sensitization level (Type 316L), and boat samples V-9 and V-10. Measurements for boat sample V-9 ranged from 0.06 to 0.09 I~/I, and measurements for V-10 ranged from 0.042 to 0.169 Ii,/I.

References 7 and 8 are included in their entirety as Appendices 1 and 2 respectively. Appendix 1 (Reference 7) reports the double-loop field testing results. It should be noted that several individual test results were discounted for the following reasons. The result of Run ¹1 for the standard labeled "S" has been eliminated from the averaging step for results on this specimen.

The reason is that this value is out of line with the other four measurements on this specimen.

The reason for the high number is not known. Runs ¹ 4 and ¹5 were made to verify that the result of Run ¹1 was anomalous for an unknown reason. The next testing was performed on boat samples V-9 and V-10. Two test results of Specimen V-9 have been discounted as follows. The test surface area of Run ¹4 included both weld deposit and heat affected zone material. The electrochemical response of weld deposit is different from wrought base material and the combined response will not represent either material. Therefore this result was discounted. The

¹ test result of Run ¹1 was discounted because the test area preparation was incorrect. Run 1 of sample V-10 was discounted because the value was twice as high as the other 4 tests. The reason was unknown, but the test result was clearly anomalous to all four of the other tests on this sample.

It should be noted that material used to obtain a calibration test result having a level of sensitization midway between the two standards was Type 316 L material. The results produced in the double-loop experiments, both with the laboratory set-up and the field set-up, were inconsistent with the test results on Type 304 material. Since the Type 316 material contains molybdenum, the surface oxides would have contained molybdenum. The electrochemical response from this surface has been reported, but was inappropriate for use as a calibration for Type 304. The DOS Tester manual (Appendix 3) cautions regarding results obtained from different materials such as Type 316 because of the incorporation of molybdenum in the surface oxide layer. All other values were used in the evaluation.

The calibration results are shown in Figure 1, and the ranges of boat sample results are superimposed on this plot. This plot has been taken directly from Appendix 2 (Reference 8).

The data indicate that boat sample V-9 has a measured EPR range from 2 to 5 coulombs/cm', and boat sample V-10 has a measured EPR range of 6 to 15 coulombs/cm. These results are consistent with the optical metallographic evaluation that suggested a slightly greater sensitization in sample V-10 than in sample V-9, although both exhibited a moderate degree of sensitization.

Page 6

I I

I

Allan Corporation Tecfatical Report TR 97181-TR-03 Revision 0 The slight differences in DOS between the two plates of material provide a rationale for the greater degree of cracking seen with the V-10 weld. The slightly higher degree of sensitization measured in the V-10 sample (compared to V-9) suggests a material condition slightly more favorable to crack initiation than the material in the V-9 sample. It should be noted that the level of sensitization in either sample is sufficient to support IGSCC. Once the cracking formed on the V-10 side of the vertical weld, the stress on the other side of the weld is greatly reduced. The material on the other side of the weld is the same plate material from which the V-9 sample was removed.

Optical metallographic evaluations and the EPR test results both confirm the potential for cracking in either plate of material. The results also confirm the appropriateness of the EPR assumption for the degree of sensitization used to predict crack growth rates with the PLEDGE modeling algorithms. The crack growth rates predicted using the same DOS parameters rates were applied in the crack growth analysis used to disposition cracking observations (References 4,5 and 9).

t

5. Conclnsions Results of EPR testing have been successfully completed on the cross-sectional surfaces of samples prepared from NMP-1 core shroud boat samples V-9 and V-10. These results indicate that both plates of material used to construct the mid-cylinder of the core shroud are in a material condition that will support IGSCC. It is further seen that the material in the V-10 sample (cracked sample) is slightly more sensitized than is the material in the V-9 sample (uncracked).

This may indicate that cracking initiated first in the V-10 material producing a crack that relieved the hoop stresses across the weld. This would reduce one of the essential parameters required to initiate cracking in the V-9 material. This action reduced the probability for cracking the V-9 material. Finally, the measured values of EPR are consistent with and support the assumptions used to estimate crack growth rates for crack disposition.

Page 7

I I

I I

Aitran Corporation Technical Report TR 971 Sl-TR-03 Revision 0 Figure 1: SL EPR Values Based on DL EPR Calibration at GE CR&D and McDermott Labs (Chart taken directly from Reference S)

SL EPRvs. DL EPR Rango of SL 0.1 EPR for V10 Wold Rango of SL EPRfor VS Wold fL'L 0.01 DL EPR: GE CRaD DL EPR: IHl/BOW UJ 0

0.001 0.0001 0.001 0.01 0.1 1 10 SL EPR ( Clcm2)

6. References

1. Azar Majidi and Michael Streicher, "The Double-loop Reactivation Method for Detecting Sensitization in AISI 304 Stainless Steels", Corrosion, Volume 40, No. 11, November 1984.

2. Kevin Hour, "Niagara Mohawk's Nine Mile Point Unit 1 Boat Sample Analyses Part II:

Dosimetery", McDermott Technology, Inc., RDD:98:55863-003-000:01, September 1997.

3. Kevin Hour, "Niagara Mohawk's Nine Mile Point Unit 1 Boat Sample Analyses Part I:

Metallography", McDermott Technology, Inc., RDD:98:55863-002-000:01, September 1997.

4. General Electric Nuclear Energy (GENE), "Assessment of the Vertical Weld Cracking on the NMP1 Shroud". GENE-523-B13-01869-043.

5. NRC Safety Evaluation Report dated May 8, 1997, regarding the results of the reinspection of the core shroud for Nine Mile Point 1.

Page 8

I I

I I

I

Allan Corporation Technical Report TR 97ISI-TR-03 Revision 0

6. Richard E. Smith, "Nine Mile Point Unit 1 Core Shroud Cracking Evaluation", Altran Corporation letter report Rom Richard E. Smith to George Inch dated April 3, 1997.

7. Kevin Hour, "Degree of Sensitization EPR Testing Results for the Nine Mile Point Unit 1 Boat Samples.", letter report from Kevin Hour to Brian Hall (Framatome Technology, Inc.),

January 14, 1998.

8. R. M. Horn, "Interpretation of EPR Measurements on NMP 1 Boat Samples", letter report from R. M. Horn (General Electric Company) to G. B. Inch (Niagara Mohawk Company),

February 6, 1998.

9. R. M. Horn, "Assessment of Crack Growth Rates Applicable to Nine Mile Point-1 Vertical Weld Indications", GE-NE-B13-01869-113, Rev.0.

10. Framatome Analysis Report: 86-1266298-00, "Fluence Analysis Report for Boat Samples Nine Mile Pt. 1", January 28, 1998.

7. Appendices

1. "Degree of Sensitization EPR Testing Results for the Nine Mile Point Unit 1 Boat Samples", letter report from Kevin Hour to Brian Hall (Framatome Technology, Inc, January 14, 1998.

2. "Interpretation of EPR Measurements on NMP 1 Boat Samples", letter report from R. M.

Horn to G. B. Inch, February 6, 1998.

3. "DOS (Degree of Sensitization) Tester, Type S-61 Operation Manual, Ishikawajima Inspection & Instrumentation Co., I.td.

Page 9

I I

I I

Altran Corporation Tecinncal Report TR 97ISI-TR-03 Revision 0 APPClldlX 1 - "Degree of Sensitization EPR Testing Results for the Nine Mile Point Unit 1 Boat Samples", letter report from Kevin Hour to Brian Hall (Framatome Technology, Inc, January 14, 1998.

Page 10

I, I

I I

I I

I

Mcoermott Technology, Inc. Research and Development Division a McDermott company ISO 9001 R 0. Box 11165 Lynchburg, Virginia 24506-1165 (804) 522-5165 February 9, 1998 Brian Hall Framatome Technology Inc.

3315 Old Forest Road Lynchburg, Va 24501

Reference:

FTI Purchase Order ¹ 60109 MTI R8:DD ¹55863

Dear Brian:

This letter incorporates Dick Smith's comments and is to provide the test results for the Degree of Sensitization (DOS) on Niagara Mohawk Power Corporation (NMPC) V-9 and V-10 boat samples that were removed from the core shroud during last outage.

The DOS Tester was provided by Dick Smith of Altran Corporation. This is a Type S-61 model manufactured by Ishikawajima Inspection 8r, Instrumentation Co. Ltd. An operation manual for this instrument was also provided with this tester and was used as the guidance for setting up this tester. Two samples identified as F and S were also provided by Dick Smith as standards to verify the adequacy of this instrument prior to actual tests. The following tables document the test results for these two standards.

Standard S Reference Value = 0.008 (engraved on the S Standard)

Standard S EC (V) IA (mA) IO (mA) IO/IA IR (mA) IR/IA Run ¹I* -0.427 9.90 -0.16 0.000 -0.16 0.016 Run ¹2 -0.434 10.96 -0.04 0.000 -0.08 0.007 Run ¹3 -0.437 11.58 -0.04 0.000 -0.06 0.005 Run ¹4 -0.435 11.30 -0.08 0.000 -0.08 0.007 Run ¹5 -0.428 10.80 -0.06 0.000 0.10 0.009

~The first run had a high IR/IAvalue. The reason was unknown.

Standard F Reference Value = 0.434 (engraved on the F Standard)

Standard F EC (V) IA (mA) IO (mA) IO/IA IR (mA)

Run ¹1 -0.451 10.84 -0.06 0.000 4.06 0.374 Run ¹2 -0.432 10.98 -0.04 0.000 4.14 0.377 Run ¹3 -0.423 12.52 -0.04 0.000 4.74 0.378 Run ¹4 -0.436 12.34 0.02 0.001 4.48 0.363 Note:

1. Standard surface was polished using 600 grit paper.

2. Field set-up was used.

3. Fresh chemical (0.5M H2SO4 and 0.01M KSCN) was prepared prior to each test.

4. Test area = 0.049 in (0.25 inch in diameter).

I I

I I

Observations:

1. Consistent results compared to the Standard Reference Value engraved on the Standard (a little low on the F Standard, however, it was believed that by adjusting the size of the test area, values close to the Reference Value could be obtained. However, the difference between F and S Standards was appropriate to distinguish between sensitized and non-sensitized materials).

2. The scatter was small.

McDermott Technology Inc. recommended to proceed with the actual tests on V-9 and V-10 met mounts and this was approved by George Inch of NMFC.

Same procedures were used for specimens V-9 and V-10 except the test area was 3.25 mm in diameter (test area =

0.0127 inch ) to allow more tests to be conducted. The following tables document the test results.

Specimen V-9 Specimen EC (V) IA (mA) IO (mA) IO/IA IR (mA)

V-9 Run ¹1 -0.399 1.98 -0.20 0.000 1.20 0.606 Run ¹2 -0.432 3.52 -0.04 0.000 0.34 0.096 Run ¹3 -0.376 2.50 -0.08 0.000 0.16 0.064 Run ¹4 -0.413 3.08 -0.06 0.000 4.22 1.37 Note:

1. See Attachment 1 for the test locations.

2. Run¹1 was not valid since the operator acknowledged that the preparation of the test area might not be appropriate.

3. Runs ¹2 and ¹3 were in the HAZ area.

4. Run¹4 test area contains both HAZ and weld area.

Specimen V-10 Specimen EC (V) IA (mA) IO (mA) IO/IA IR (mA) IR/IA V-10 Run ¹I -0.472 3.76 -0.10 0.000 1.22 0.324 Run ¹2 -0.449 4.60 -0.00 0.000 0.78 0.169 Run ¹3 -0.386 2.72 -0.10 0.000 0.44 0.161 Run ¹4 -0.375 2.82 -0.10 0.000 0.12 0.042 Run ¹5 -0.351 2.78 -0.10 0.000 -0.34 0.122 Note

1. See Attachment 2 for the test locations.

2. It was unclear why IR value for Run¹5 was negative. This value was questionable until further clarification is obtained.

3. Run ¹1 was conducted in the base metal area. The IR/IA value was high compared to those from the HAZ metals.

I Finally, a sample (specimen ID ~ K34043-2) was received from Ron Horn of GE Nuclear Energy. This sample was tested using the same setup used for the actual tests for comparison purpose.

GE Specimen K34043-2 (DI EPR (IR/IA) = 0.025)

Specimen EC (V) IA (mA) IO (mA) IO/IA IR (mA) IR/JA K34043-2 Run //I -0.373 15.20 -0.14 0.000 0.32 0.021 Note:

1. Test area = 0.25 inch .

2. Test results (IR/IA = 0.021) were close to the expected value (IR/IA = 0.025).

Please forward data presented here to George Inch of NMPC and Dick Smith of Altran Corporation.

evin Hour Ct: L. J. Ferrell File

I METALLOGRAPHYSPECIMEN V-9-M

I I

I' I

I I

I

METALLOGRAPHYSPECIMEN V-IO MET I

I Allan Corporation Technical Report TR 97181-TR-03 Revision 0 APPendiX 2 - "Interpretation of EPR Measurements on NMP 1 Boat Samples", letter report from R. M. Horn to G. B. Inch, February 6, 1998 Page 11

I I

I I

I I

I

February 6, 1998 To: G. B. Inch From: R. M. Horn

Subject:

Interpretation of EPR Measurements on NMP1 Boat Samples cc: R. Smith, S. Ranganath, T. M. Angeliu Efforts were undertaken by McDermott Labs, under the direction of Dick Smith and Kevin Hour, to quantitatively measure the sensitization level in both the o.d. V10 and the i.d. V9 samples. The IHI Double Loop (DL) EPR Field unit was employed. This system used a special cell to hold the electrolyte and evaluates a small area of the material. This also allowed measurements to be made in areas adjacent to the crack in the V10 met sample. The values are given in Table 1 as transmitted by Dick Smith of Altran. The values are not easily converted to the Single Loop (SL) EPR values that have been used in the PLEDGE crack growth model. However, the IHI system includes two different reference standards for use in calibration. These standards are at extremes of sensitization: one non-sensitized and one highly sensitized. In that the IHI procedure was developed for field use, the standards provided a means of comparing the IHI measurements on the boat sample material to well controlled laboratory tests thereby allowing an assessment of the single loop (SL) EPR values that are used in the PLEDGE crack growth rate model.

The laboratory evaluation was performed by GE CRUD Lab under the direction of Dr.

Tom Angeliu. The DL EPR were performed following the standard approach;

1. Surface was ground using 600 grit paper

2. Used DL-EPR procedure of Akashi et. al.

3. Fresh solution vs. old solution made no difference 4 Test area 1 cm The SL-EPR conditions were as follows:

1. 1 micron polish surface finish

2. Procedure of Clark, et. al. 30'C, 1.67mU/s, +200mUsc~ to -400mUsca

3. Data were adjusted to account for the grain size using Pa=Q/(specimen area*[5.095x10-3exp(0.34696*ASTM grain size at 100X)], according to Clark, et. al.

Measurements were made on the IHI standards at both labs. A summary of the measurements are given in Table 2. The table displays the measurements from both labs for the two standards as well as the quoted values provided by IHI for the two pieces of

I I

I I

I I

I I

I

stainless steel. The table also displays the SL EPR values on the same material, measured by GE CR&D. These values provided a means of correlating the DL EPR to SL EPR and could be used to interpolate to SL EPR values for the boat samples. This process could be used (1) to verify that the EPR values used in the crack growth modeling were appropriate and (2) to give an estimate of the sensitization level using the conventional SL EPR values that have been commonly used in the literature. This would back up the efforts made to make metallographic comparisons. Figure 1 displays the conversion of DL EPR to SL EPR values based on the measurements on the standards. The log-log~ g'~

relationship between DL EPR and SL EPR has been discussed in the literature by ~( "l<<

Streicher. It is clear that the IHI system tends to produce higher values. This could be expected due to the nature of the field process and the smaller area examined. The end points are set by the GE CRUD SL EPR measurements. The plot also shows the range of measured values for the U9 and U10 samples. These values are shown as a region between the two lines. This approach shows that the V9 predicted SL EPR values would range from 2-5 C/cm and the V10 values would range from 6-15 C/cm . These values are consistent with the metallographic determined values and the values used in the crack growth assessments.

In summary, efforts were made to correlate the DL EPR values measured on the NMPI boat samples. This was performed by benchmarking the IHI field cell measurements at GE CR&D Laboratory. The assessment established that the SL EPR values that were assigned to the V10 cracked boat sample were consistent with the values used in the crack growth analysis.

Prepared by:

R. M. orn, Engineering Fellow Materials Technology Reviewed by:

S. Ranganath, ngineering Fellow Structural Mechanics

g I

l I

I

~ ~ 0

~ ~ ~ ~ ~

~

f

0. ~ I ~

~

I. s

~ ~

I. ~

~ ~ ~ o ~ ~ f

~ ~

~ ~ ~ ~ ~ ~ I III ~

~ ~ I ~

~ i ~ ~ ~ ~

~ i ~ ~ ~ ~

~ i I lll I

~ ~ ~

~ ~ .

~ ~ ~ ~ ~ o

Figure 1: SL EPR Values Based on DL EPR Calibration at GE CREED and McDermott Labs SL EPR vs. DL EPR Range of SL 0.1 EPR for V10 Wold Rango of SL EPR for V9 Wold 0.01 DL EPA: GE CR80 DL EPR: IHI/Baw 0.001 0.0001 0.001 0.01 0.1 10 SL EPR ( C/cm2)

Aitran Corporation Technical Report TR 971 Sl-TR-03 Revision 0 APPendiX 3 - "DOS (Degree of Sensitization) Tester, Type S-61 Operation Manual, Ishikawajima Inspection & Instrumentation Co., Ltd Page 12

I I

I

DOS (Degree of Serisitization) Tester Type S- 8>

OPEARATION MANUAL ishikawajima inspection 8 instrumentation Co., Ltd.

I I

I I

I I

I I

(1) DOS TESTER can accurately measure the degree of sensitization of 300 series stainless steel within a short operation time.

(2) The electrochemical potantiokinetic reactivation method (EPR method) is utilized for the evaluation of intergranular corrosion and intergranular stress corrosion cracking susceptibility.

(3) The criteria used in DOS TESTER to evaluate the degree of sensitization is the peak current ratio (Ir/Ia) in both anodic and reverse polarization processes, which improves reliability and accuracy compared with conventional technique..

(4) DOS TESTER controlled by a microcomputer interlinke with a potentiostat is fully automatically operated and analytical results are printed out on a tape.

I I

I I

2. SPECIFICATIONS Drift 0.10mV/ '6 Responce speed 10 -2sec Input resistance 10-- ohm max (C capacity 150 PF)

Setting Potential- 0-4V, ldig. lmV Minimum scale of potentiometer---- 0.05V (class 2.5)

Electrolytic current 0- 80mA Minimum scale of ammeter---------- 1-100mA (class 2.5) 3 ranges Current record sensit ivily------- 0.15mA Potential record sensitivity---- 0.25mV Power supply input AC 100V 50/60Hz

3. COMPOSITION DOS TESTER consists of the following main package and accessories.

3-1 Main package Power supply unit Input power supply AC 100V (50/60HZ),

Potentiostat unit IC potential DC amplifier Electrolytic current output circuit Indicating potentiometer (Electrode potential meter)

Regulated power supply Regulated power supply for electrolytic current Electrolytic current measuring circuit Setting potential adjusting circuit

• Computer unit CPU (Z-80A)

ROM (Arithmetic and sequence control)

RAM (lK words x 2) data memory interface data storage

• Printer Printer (Dot type, 15-digit pneumeric thermal printer)

I I

I

3-2 Accessories 1.Reference electrode 2.Platinum connter emectrode 3.Electrolytic cell for field measurement 4.Electrolyte injector 5.Bonding agent 6.Sandpaper 7.Thermometer (A) 0 -100'c,l50mm (encased)

B..Power cord,3m 9.Coder for counter electrode and specimen 10.Reference specimen (Type304) 12.Electrolyte vessel 3-3 Package dimensions 300mm wide x 350mm deep x 140mm high

I I

I I

I

4. PROCEDURE Turn on reset switc Turn on start switc -------Operation start Measurement of open circus .-----Measure activation condition on testing surface potential (EC)

Cathodic reduction -----Perform treatment one-minute cathodic reduction treatment at -1.0V Printout '.open circuit when the open circuit potantial exceeds -0.35V potential (EC) Stop -----Operation stops and alarm sounds, if the open circuit, potential exceeds -0.35V even jfter repeating the cathodic reduction treatment twice.

EC ERROR rintout Anodic polarization start -0.45V -----Continuously polarize from -0.45 te passive potential I

Anodic polarization end Sto -----Operation stops and an alarm sounds, flows excessively.

if the anode current Measurement and printout in anodic polarization process peak current (Ia)

Measurement and printout passive state holdin current Io 'I Calculation and printout Io/Xa Sto -----Operation stops insufficient or I

and an alarm sounds, Ia is small and Io/Xa if the 0.01 passivation is Reversed polarization start -----Continuously polarize to cathodic direction Reversed polarization end -0.4V Xo/Ia ERROR rintout Measurement and printout in reversed polarization peak current (Ir)

Calculation and printout of Ir/Ia Operation stop Turn off reset switch 9$ 03oQQg(Q- Q Turn off start switch End (operation time takes about 15 minutes)

f Printing example NO XX Address number EC 0.420V ---------- Open circuit pontential Vvs SCE Ia 10 90MA--------Anodic polarization maximum current mA Io 0 02MA---------- Passive state current mA Io/Ia 0.01 Io to Ia ratio Ir 00.12MA---------- Reversed polarization maximum current mA Ir/Za 0 001---------- Ir to Ia ratio (Reactivation ratio)

Error display example EC ERROR When open circuit potential exceeds

-0.35V even after repeating cathodic reduction treatment twice AD OVER RANGE-------- When anodic polarization current overflows Zo/Ia ERROR---------- When passive state is insufficient or Za is small and Io/Ia) 0.01;

I I

I I

OPERATION PANEL gPA-

"DDS-TF.STER 4qoa'35>

QW~@gp; 8[

(1)Power switch (8) Voltmeter (2)AC power socket (9)Recorder term-(3)Working and counter inal(current) electrode connector (10)Recorder term-(4)Reference electrode inal(potential) connector (11)Mode indica-(5)Reset Switch tion panel (6)S'tart switch (12)Printer (Z)Ammeter ( 13) Tape deri ver

I I

I I

I

ACCESSORZES gfpa:

g . ~>> C~v. 4,<<

<<W r

( 1) Re ference electrode --.- -------- --- --. 1 pc.

(2) Cord for counter electrode and specimen 1 pc.

( 3) Power cor> 3m -- ------------ ----------- 1 pc.

(4) E lectrolyte vessel ------.--------------------2 f W pcs ~

(5) Electrolytic cell for field measurement 1 06 2 pcs 1 2 pcs ~

(6) Platinum counter electrode ---- -----------1 pc.

( 7) Electrolyte inj ector --- -- ---------.-----=1 pc.

( 8) Bonds.ng agent - -----------------.---1 pc.

(9) Cord for counter electrode and specimen ------1 pc.

(10) Thermometer (A) 0'-100'C, 150mm (encased) 1 pc.

(11) S andpaper -------- ----

-- ----------"-- 5 sheets (12) Reference specimen (Type 304) 2 pcs ~

I I

I I

5. ASSEMBLY I

I I

I I

I

Connecting method of electrode cord and recorder terminal.

(1) Electrode cord connector (2P)

(a) red clip ...... Connect to platinum counter electrode (b) black clip .... Connect to specimen (2) Reference electrode connector ..... Connect to Ref. electrode

. (3) Connection method of recorder terminals A-. REC ........ Connect to current recording terminal.

V-REC ........ Connect to voltage recording terminal.

6. OPERATION 6.1 FIELD MEASUREMENT Reference.

electrode Platinurrr counter electrode Electrolytic cell Specimen FIELD MEASUREMENT (1) . Remove dirt and scale from the specimen surface.

(2) Polish the testing surface with sandpaper.

After uniformalizing the polishing traces of sandpaper in one direction, polish the testing surface again to the parpendicular direction until the polishing traces are completely eliminated.

(3) Degrease the polished surface with acetone or thinner.

I I

I

(4) Filg the electrolytic cell to meet the shape of the specimen by applying a sandpaper to the testing face until their bonding faces meet each other.

(5) Bond the electrolytic cell to the test surface.

If the testing face is tilted or vibrating, depress the testing face by hand or fix it by using a tape until the bonding agent is fully dried up.

(6) Make sure that the bonding agent has been dried up and the cell does not move any longer.

(7) Prepare electrolyte as informed in next section (8) Inject electrolyte into the electrolytic cell to an 80@

level.

(9) Fix reference and counter electrode into cell as shown in illustration. Keep a space of about 10mm between the tip of reference electrode and the specimen surface.

Be care that the platinum counter electrode does not touch the specimen.

(10) Connect electrode cords to operation panel connectors.

(11) Connect the working electrode turminal to the specimen with solder or clip.

(12) Turn on the power switch.

(14) Push the reset button. (Make sure that the reset button in lighting)

(15) Push the start button. (Make sure that the start button in lighting)

Measurement is completed about .15 minutes after the start button has been lit, and measuring results are recorded on the printer. when measurement ends, an alarm sounds to inform you of it for 1 minute.

(16) Push the reset button.

(17) In case of abnormal operation conditions, measurement is interrupted, an alarm sounds and some error messages are printed out.,

(18) After completion of all measurements,'urn off the power switch, and suck the electrolyte by using an injector.

(19) Rince cell, electrodes and specimen with fresh water.

I l

I

6. 2 LABORATORY MEASUREMENT CE Reference electrode Platinum counter electrode Specimen LABORATORY MEASUREMENT (l) Cut the specimen to a suitable size. The testing surface should be about 50mm 2 (2) Solder a lead wire to, the rear of the testing face.

(3) Embed the specimen and insulated lead wire into reSin.

(4) Polish the testing surface in the same manner as, in "field measurement".

(5) Degrease with acetone or thinner.

(6) If the testing surface is larger than 50mm , adjust the area by covering with enamel resin (manicure or the like).

If a clearance is produced between the specimen and resin, cover the clearance with enamel resin.

(7) Put electrolyte into the electrolytic cell more than 200ml.

I l

+/

I I

l

(8) Dip the platinum counter electrode, reference electrode and specimen into the electrolyte. Keep a space between platinum counter electrode and the specimen so that they are not shorted with each other.

(9) Connect the electrode cords to operation panel connectors.

(10) Turn on the power switch.

(11) Turn the current range knob from OPP to 100mA.

(12) Push the reset button. (Make sure that the reset button in lighting)

(13) Push the start button. (Make sure that the start button in lighting)

Measurement is completed about 15 minutes after the start button has been lit, and measuring results are recorded on the printer. When measurement ends, (14) an alarm sounds to inform you of Push the reset button.

it for 1 minute.

(15) Incase of abnormal operation conditions, measurement in interrupted, an alarm, sounds and some error messages are printed out.

(16) Rince the specimen with fresh water.

I I

I I

I

8. TROUBLESHOOTING (1) The power indicator lamp does not light when turning on the power switch.

Is power cord connected in case of AC power supply  ?

(2) The measuring voltmeter and ammeter pointers fluctuate during start button is lighting.

Are the electrode cords connected to the terminals correctly  ?

Is the reference electrode set correctly with normal continuity 7 Is the platinum counter electrode separated from the specimen without any contact Are the platinum electrode, the reference electrode and specimen dipped into the electrolyte 'P (3) A measuring operation is always interrupted with some error information.

Fully polish and wash the measuring surface again.

Adjust the measuring area in case of low temperature condition.

Use the special electrolyte for Mo containing stainless steel.

Check the reference electrode.

13

9 CAUTIONS Though this electrolyte is not a noxious substance, be careful with handling so as not to scatter it.

Wear rubber gloves. If your hands or skin was contaminated with electrolyte, wash it out with running water.

If your eyes should have been contaminated with it if or you should have drunk it by mistake, take an emergency measure like washing, vomit, etc., and consult a doctor at once.

(2) Xf electrolyte leaks and attaches to the internal mecha-nisms of DOS TESTER, it may corrode them to cause a trouble. Particularly be careful with its handling, accordingly.

(3) Treat the waste electrolyte by a suitable waste solution treatment vessel after neutralizing it.

(4) Be care for handling the reference electrode.

Keep the ceramic tip wet condition. Confirm the KCl cristal in the solution.

When the bubble is recognized at the point of "A" in the figure, shake the electrode softly and remove KC1 cristal bubble to the upper side.

I I

I

Electrode cord Seal Hole for injection of KCl Standard electrode body A

Crystal of KCl Ceramic

'Cap f'r prevention of drying REFERENCE ELECTRODE 15

I l

10. TECHNICAL INFORMATION 10-1 PREPARATION OF ELECTROLYTE Two kinds of electrolyte are recommended for DOS, TESTER as shown in Table l.

Though the standard electrolyte (0.5M H2S04 0.01M KSCN) can be used for various kinds of stainless, steels, the concentrated electrolyte (1.0M H2S04 O.lM KSCN) is prefer for Mo contained stainless steels such as type 316, which anodic current (Ia) is smaller than that of non-Mo material in case of low temperature condition.

The example of preparation is shown in Table 2.

Table 1 Recommended electrolyte Electrolyte H2504 KSCN Standard 0.5M 0.01M Concentrated 1.0M 0.1M Table 2 Pr epar at i on example Electrolyte Water* H2 S04** KSCN ~Deionized Water Standard 1000ml 29ml 1.0g Concentrated 1000ml 60ml 10.3g **95 10-2 SELECTION OF THE TESTING AREA Ia (anodic polarization peak current value) and Ir (reveresed polarization peak current value) depend upon the testing temperature.

Fig. l indicates the temperature dependency of the current density,Ia of 304S.S. as an example.

I I

I

As temperature becomes lower, the current density decreases.

It is desirable to use a larger cell to improve the measuring accuracy. Accordingly, it is recommended to select the suitable testing area as shown in the table in case of 304 stainless steel.

As Ia of Mo contained stainless steel such as type 316 is lower than that of 304, larger diameter electrolytic cell may be used.

TABLE 3 RECOMMENDED TESTING AREA (304S.S.)

Test temperature TESTING AREA 10'C 0.5-2cm 2 14$

20~C 0.3-1.3cm 10-146 30oC 0.2-0.8cm 10$

40 C 0. 1-0. 4cm 2 10$

200 0 iso

~4 C

o IOO 50; lO 20 30 40 TEMPERATURE (~C)

Fig. 1 Temperature dependency of Ia (Type 304) 17

I I

l I

10-3 TEMPERATURE CORRECTION The 'reactivation ratio (Ir/Ia) indicates the temperature dependency. Fig. 2 shows the EPR test results at respective temperature, regarding many specimens having different degrees of sensitization When comparing test results at different temperature with each other, it is recommended to compare them after converting them into test results at the same temperature(30 C, for example) according to Fig. 2.

How to use the chart.

Example 1 If you measure 7  % o'f value at 30 C is read to be Ir/Za at 15 C, the equivalent Ir/Za the equi.Ir/Ia line.

17 % as indicated on Example 2 If you measure 3 % of Ir/Za at 15 C, reasonabley separated in between the you must draw a line two adjacent chart lines to read 8 % of 30 C equivalence value.

I I

I I

I

100 50 leal jjjil!li.

s ~e

'e! ~

ji!l iii i !lit

~

~ ~ ~

elis I ~ ~

i it t!It

~

iij'!1 Ijt

'sl sis!

,'si! I j('.I

~

I!I'"I ! !!I'i.'i!e!s

,js ,js:

J Its Jt

~

(I!

ts

~ e st'.

l!!i i!!! I:!j'j I:I

~

a I

s,l ~ si t! ',I'.I' ii;I 'I tjj!

te' JI titt II !I;:

~

. its tata!a!i! :! I !!ls el!!i!s'I

'I'I!j

~ e Qli L,!j I!!I tst e

~

ltj! sit ~ alta

!i!I :I>>

~

s I'

~~

',l:,

s ,;!Ij lit s

sttj II ~"

'tl'jia alia I ~

~ ~

e .Ies ~

j'ale] ~ .It s

s

!i'

!>>i I~

~

tats test

!~

s

~ ~

."I

!sti "Isa e

~~

tts .'Iit I

I ~ !s

~ e

!!! !!J! !lji Isla!I;,1 s s ttt;'lij

'll'j at es a iji: i eti at

! alla s ~

e

.I o~

e s

tt

~

.;j ,j;!

s!s ss!'ee at!i

~

>>:!! !i s~

J ss i

e ~

sj!I Jl ~ I

~ '

!ili~l

'::-I':J

..attests !Jts

!!i<<sit ls<>!

I!

I t "s

~

~

~

~

e ~

~

ts se e

~

st j'I', I I!! I!I '.!j. tt ~ ~ e Il!l ' ~ ese i!it ls!! Ist tats~l ';I'ijiii' i!ij I!s s

ijii I',!! :ii it!,.

e e Ij eels ei!I II s a'i) s ~~

~

~ ,sjj  !!jl ~

s JI j I lo'ih i' i s; js jsss illJ J' jjl jil, Jtit s

~ ~ ~ s ~~ sst:

~

lit!

~

t

.Jal I!Ii tl j Ill! sill JJ:I :-i! ! I ji!:

~ r ijl! !lit t'i I'

jjii !:! il(i jl e!

l/ii 'i il

~ e Ia ~~ ~ ~ \ ~ ~ ~

!: j lie: des!

".':ii! (I il

~ ~~ ~ ~ ~~ ~ ~~

~ Ie  ! e.'e

~ ~ e

~ ~e il  :.!

~~~

~~

~

~ ~

~

/I ~ ~ ~ ~ ~ ~ ~~~~ ~e ~ ~~~e

~~ ~ s~ ~ ar a

~ e ~

.-Ll.I Lar ae 'ju ;I" .'Il jill I Is! isl: e ee ~ ~

~

ree ~

~ 'll'I:

~ ~~ ~

~ kl ~

~~

~~

e e

~ ~~

~~ ~

~ e ~

er

~ ~ ~ ~ ~

~ ~ ~ ~ ~ ~ ~ ~

I I ~ ~ s sot! I

~ ~

e ~

~~

s ~ ~ ~ ~ ~ ~ etees  !!al ',iss ~e ~~ ~

ass I!I ~~ ~ ~~ e

~ ~ e e I

s ~

jll,

~

tee sile j."si s !s ~ I ts ~ ~ ~ e ~ sat ~

'I" isa!

~

~~~

~~ s ~ ~ s

~

ace

~~~

~

j!IlijjIJ!!' ~ ~ ~ ~ t III ~~ ~ tess s ~ ~

tateeJ

~~ ~~

..s <<lss s esj ~

t~s ~

sl ~

t'tt iel'I t si

, ss ~ ~~ ~~ ~ des ~

set ~~~

~ ~~ e

~

~~ e sl ~ tta ~

at ~ ~

s ~~ ~

~

s at ~ ~

e ~ sill '!i's

~ ti tt I stet ~ ~ ~ '.ll,'ts! battiest' ~ ltl s ~ ~ t istsi. ~ e ~ t ~e stat tail

~ ss ~

~ ss  ! I ~

atheists. des ~ ~ s ~ .Jt. ~~ e ~ ,s jjal Iles e ~ ~ , ~ ~ I~ t ~ t st ~

e ~ ~ s

!!I it! t!I! sa I!s t>> Is!) ' !I Isa sl ~ s ~ te !e eeet

':I"" ~ ~ e a+ ~ ~ ee sees,

~ ~ ~ s

~ 1st til !als

~

Js

~

~ s e ~

~

i

~ ~

I!

I~ s ~ ~ It ~ des

~ ~ ~

~ III

~ ee ~

s ~ t ~ rica 1st! !!ss e ~

,J sss e ~ ls 's l!!s j:jt es ~ ~ e ea ~ irate ~

Il)i lj'i lwill

~ te ~ ~ ~

J.t i !are 10 !sl!': s

!iJ!I!!:.

s.. lat.. J~

I i,:I',ill llj! iiii

! Ii IIII Uii I" '

t~s

~

~ eL to $ ~5 ijI jiia e

~ sr I Isa. ~

s ~

I

~ s

~ e ~ ss a

' Ig! !

takeit.ii .:::i'I;..., i!j! iiii

,~s

~ s!li I)jl fili !!i! II)i . hei isli ;!I! !et'ati t!itliilj l)l i::.' "ss 'sa s~ I!Jl stat ji: I'; s jil! i JJJ tttl lilt Jl! iiii jiaal

. ~ Ji .j:I I Jti!

L'ilill'ill ijij ts, 'llt ilit ILi't:

! ijl jt:I '.'I :I! I:I e'ttt tlt's se ..Ist.!t !j  !!I: !I: ~

'll:i:. ~

I 'e I)!I jIIe .'.:. ~

.!li 5

It s

~  !!l ssi. s!Ii i'l ',st',:,:

Ii jii sIjl ili s

1,"Ii

!i!. l ii !Ill s!i U!s I ~

I jul j>>tj t

j

~

II tjjj

!lti

'ass! ..Js!!! jilj :j!I !Itj I!a  ;'.'!

i!t!

~ I I!;

j:I;I! . I ti!

~

j!I! ' ttt. II 'il  !

tll Iili ,.Js :I t ti !j!i e

.s

. '! lil'

~

il i is I!Ij!ii~j lss lij alla ill' eJ IJJJ i

l !I I .jiJ oJ .J,tj!J I' il'! '!

tt Illa I' I'I

~

t  :

j ji:li: Ijji j!:

i!i! '."

~

i ~  ! JI!>>I ~

I',II

lli

!,II IIil I)Ij

~ ~

I)i !Il i ~~ ~~ ~

e

~ e !I!'I

' ~ ~ ~ os

!il', :;! !I sill i. ~ ~ eee ~~ e

~ e ~s bill

~ ~

i ! ii:f I."I illi .!i i!!i ~ ~

as ~ ~~

~ a js ~

s ~

e e

~ ~

e e ~~ ~

sees eee ~ ~

e ~

sees I' j!I ~~

e eet ~

!!I! sis e ss s~

stat stet II!av seel

~ ~ e ie!

l e~~ ~s ~

iil'!

et !s ~ ~ ~ ~

~ eee

~

a. ~ att 'sill'.sl jl jill ~

~ s' et t t~s~

~ o ~ ~~

'Ill Ii/', stoa et e ~

~ s s s ~ e ~~ ~ ~

s ~

ei ~ s t

~

~ t iii!L~ II!l ill! Ii,'I e

li,'", etta ,'li'j,I ste ~ ~

~ s ~

I l>>t I ~ se ~ ~ ~~ e

,'I' ~s ;iiilj:Ij !Ji! ,Ifs stat tst I

ts tss

~ ~ teal I ~

sit stat et!I I ~ ~ ~ ~ st!s

!tel tlat se ~s sale st.

~ ~ est ie ~ i

~

a.,j.

~e ~~

ts tsl ills ti!I tait ,It

~

slt iiji sit lite

~

!il Jl,l lii sil, stot I .ae

~ set Inst Slee I!sl

~

'Js ~ t!

~ ~ eet

!e!e Ilii s!

~

! ~ t I~ ~ s

'!II

!I al ti Is 'ate sist  !!tt sill all! ltII

~

al.eee I!I: /ts .ttj lI

~e I a ~ e s.t !

~ ~ e i! j!ij ,! ,! ' ttt !I !iis asl. I!I Ie !Its JI:I !e. Itisset

! at

~ ~ ~ s ~ ~ ~ s ~ s ~

s

~ .! til ill! it !,I, j~iij i

.I !I!

I e ~

s Ii! lip llali!ij:

'i t'ai II s':Li;:

iIj III II!I I.isa

'I:I !4l

!li! stijl jlij set i!!I it!Ilst

'iii ~ s j<<!

's:

j':

Lis s! t tst illa l :s'e li'tti i' I>>' at li ,jli IJi tats Ui tel s s~

j>>t I Lsi .ss

~

I ~

~t~sii I t lj>> i j S ~

,s l:: e iili is ~ sass s, ~

~ ii!j jiij

': tjl 'I:

l j!' tjl ,I.. ..Jt "I ! I s;

j el

~

~

j 'j:I I ~

!! It s! tj. t s!

~

0.5 I

~

i ~

I,.

~~

ii" !" II Ii ~ ~

.lij !as ett I,  !'

'Is) il !fj ~

I et I at'!

e

!ai

~ ee a!s s

e

~

s!

ei

.  ! o des I.  !

10 -15 .20 25 50 55 40 TEMPETATURE (. C)

Fig. 2 Temperature correction chart of ir/Ia (standard solution)

I 10-6 MEASUREMENT OF Mo CONTAINING STAINLESS STEELS Since Mo has the effect of depression of the dissolution in ac'tive state, the anodic peak current (Ia) in Mo

'ontained stainless steels is decreased in poralization process though the passive state holding current (Io) is not changed.

The ratio of Ia to Io, therefore, frequently exceeds 1/100 and DOS measurement is interrupted with error message.

Expansion of testing area, increasing of environmental temperature and application of special electrolyte are required for improving the stability of measurement.

It is also necessary to keep about 3 minutes in electrolyte before starting operation in order to dissolve" the remained oxide film on testing surface.

20