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William Corbett, Carly McGee and Jason Coley KTA-Tator, Inc.
Too Deep or Too Shallow… Can Surface Profiles Be Changed by Additional Abrasive Blast Cleaning? Author & Presenter: William Corbett, PCS Co-Author: Carly McGee, PCS William Corbett, Carly McGee and Jason Coley KTA-Tator, Inc. © 2007 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries. The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.
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Origin & Learning Outcomes
Research Conducted in 2016 Technical Paper Presented at SSPC 2017 Conference Abbreviated Version of Technical Paper Published by JPCL (February 2019) Learning Outcomes: Describe the process of generating a surface profile; Recognize the impact of insufficient or excessive surface profile on coating performance; Describe the process of increasing or decreasing surface profile; and Recognize the impact of reducing surface profile on peak density/count
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Background & Problem Statement
Coating specifications invoking abrasive blast cleaning generally contain surface profile requirements Imparting surface profile enhances mechanical adhesion and helps resist undercutting corrosion Insufficient or excessive surface profile can be problematic Measurement of surface profile is a frequent hold point inspection
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Background & Problem Statement
Several factors influence surface profile depth Nozzle distance and angle Compressed air volume & pressure Abrasive type, size & hardness Substrate type & hardness Presence of pre-existing profile Preparation of a test area can be advantageous
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Background & Problem Statement
Some evidence that a shallow surface profile can be deepened using a larger abrasive Re-profiling presents challenges for blaster and QC Re-profiling doesn’t change appearance Confirming 100% of the surface has been re-prepared is difficult
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Background & Problem Statement
Excessive profile caused by: Existing surface profile from previous work “Softer” steel Selection of an abrasive that is too large Can surface profile depth be reduced by re-blast cleaning? Does parallel re-blast work? Is peak density/count reduced? Re-profiling presents challenges for blaster and QC
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Experimental Design – Phase 1
Included two abrasive types Mineral (Garnet) Ferrous Angular (Steel grit) Effect of Re-Blast Cleaning Existing Shallow and Deep Surface Profile Plate No./ Abrasive Quad 1 2 3 4 Re-blast (Larger1) (Larger2) (Smaller1) (Smaller2) 1, 2, 3 (Mineral) 1-mil MS Quad 2-4 4, 5, 6 (Ferrous) 7, 8, 9 (Mineral) 5-mil 10, 11, 12 (Ferrous) MS: Mill Scale 1 Used a mineral abrasive to generate a nominal 2-3 mil surface profile 2 Used a ferrous, angular abrasive to generate a nominal 2-3 mil surface profile
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Experimental Design – Phase 2
Included two abrasive types Mineral (Garnet) Ferrous Angular (Steel grit) Effect of Parallel Re-Blast Cleaning of an Existing Deep Surface Profile Plate No./ Abrasive Quad 1 2 3 4 Re-blast1 (Parallel; ~30°) Re-blast2 13, 14, 15 (Mineral) 5-mil Quad 1-2 only 16, 17, 18 (Ferrous) 1 Used a mineral abrasive 2 Used a ferrous, angular abrasive
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Experimental Design – Phases 1&2
Methods Used to Characterize the Surfaces ASTM D4417 Method B (depth micrometer) Method C (replica tape/micrometer) Peak Density (optical grade replica tape with reader) ASTM D7127 Stylus Instrument for Peak Count (Rpc) Three-dimensional microscopy
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Experimental Design – Phases 1&2
Frequency of Measurements ASTM D4417 Method B (depth micrometer): 10 per area, averaged Method C (replica tape/micrometer): 2 per area, averaged Peak Density (optical grade replica tape with reader) 2 per area, averaged ASTM D7127 Stylus instrument for Peak Count (Rpc) Five traces per area Three-dimensional microscopy One image per area
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Test Results Variable No. 1
Shallow profile (e.g., 1-mil) with Garnet. Can it be increased with a larger abrasive? Technique Attributes of Initial Blast on Mill Scale (Q1) Attributes of Second Blast on Mill Scale (Q4) Attributes of Re-Blast (Q2 & Q3) Depth Micrometer 1.5 mils 2.2 mils Replica Tape 2.0 mils 3.0 mils 2.9 mils Peak Density 17/mm2 14/mm2 16/mm2 Peak Count 83/cm 67/cm 69/cm Characteristic Yes No % Change Did re-blast increase surface profile? X +32%1 & +31%2 Did re-blast change the peak density? -6% Did re-blast change the peak count? -17% 1Depth Micrometer 2Replica Tape
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Test Results Variable No. 1
Initial roughness with smaller abrasive (Q1) Roughness generated by re-blast with larger abrasive (Q2)
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Test Results Variable No. 2
Shallow profile (e.g., 1-mil) with Steel Grit. Can it be increased with a larger abrasive? Technique Attributes of Initial Blast on Mill Scale (Q1) Attributes of Second Blast on Mill Scale (Q4) Attributes of Re-Blast (Q2 & Q3) Depth Micrometer 1.8 mils 2.6 mils 2.5 mils Replica Tape 2.7 mils Peak Density 20/mm2 13/mm2 12/mm2 Peak Count 116/cm 76/cm 77/cm Characteristic Yes No % Change Did re-blast increase surface profile? X +28%1 & +33%2 Did re-blast change the peak density? -40% Did re-blast change the peak count? -34% 1Depth Micrometer 2Replica Tape
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Test Results Variable No. 2
Initial roughness with smaller abrasive (Q1) Roughness generated by re-blast with larger abrasive (Q2)
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Test Results Variable No. 3
Deep profile (e.g., 5-mil) with Garnet. Can it be reduced with a smaller abrasive (nozzle perpendicular)? Technique Attributes of Initial Blast on Mill Scale (Q1) Attributes of Second Blast on Mill Scale (Q4) Attributes of Re-Blast (Q2 & Q3) Depth Micrometer 4.6 mils 2.1 mils 2.8 mils Replica Tape 4.8 mils 2.9 mils 3.8 mils Peak Density 6/mm2 17/mm2 7/mm2 Peak Count 49/cm 66/cm 57/cm Characteristic Yes No % Change Did re-blast decrease surface profile? X -39%1 & -21%2 Did re-blast change the peak density? +14% Did re-blast change the peak count? 1Depth Micrometer 2Replica Tape
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Test Results Variable No. 3
Initial Peak Density (Quadrant 1) Peak Density Generated by Second Abrasive on Mill Scale (Quadrant 4) Peak Density Generated by Re-Blast (Quadrant 2, 3)
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Test Results Variable No. 4
Deep profile (e.g., 5-mil) with Steel Grit. Can it be reduced with a smaller abrasive (nozzle perpendicular)? Technique Attributes of Initial Blast on Mill Scale (Q1) Attributes of Second Blast on Mill Scale (Q4) Attributes of Re-Blast (Q2 & Q3) Depth Micrometer 7.0 mils 2.4 mils 3.1 mils Replica Tape 5.9 mils 2.6 mils 3.7 mils Peak Density 5/mm2 16/mm2 6/mm2 Peak Count 36/cm 77/cm 54/cm Characteristic Yes No % Change Did re-blast decrease surface profile? X -56%1 & -37%2 Did re-blast change the peak density? +17% Did re-blast change the peak count? +33% 1Depth Micrometer 2Replica Tape
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Test Results Variable No. 4
Initial Peak Density (Quadrant 1) Peak Density Generated by Second Abrasive on Mill Scale (Quadrant 4) Peak Density Generated by Re-Blast (Quadrant 2, 3)
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Test Results Variable No. 5
Deep profile (e.g., 5-mil) with Garnet. Can it be reduced with the same abrasive (nozzle parallel; ~30°)? Technique Attributes of Initial Blast on Mill Scale (Q3 & Q4) Attributes of Re-Blast (Q1 & Q2) Depth Micrometer 3.9 mils 5.6 mils Replica Tape 4.4 mils 5.2 mils Peak Density 5/mm2 4/mm2 Peak Count 58/cm 50/cm Characteristic Yes No % Change Did re-blast decrease surface profile? X +30%1 & +15%2 Did re-blast change the peak density? -20% Did re-blast change the peak count? -14% 1Depth Micrometer 2Replica Tape
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Test Results Variable No. 5
Initial Peak Density (Quadrants 3 & 4) Peak Density Generated by Re-Blast (Quadrants 1 & 2)
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Test Results Variable No. 6
Deep profile (e.g., 5-mil) with Steel Grit. Can it be reduced with the same abrasive (nozzle parallel; ~30°)? Technique Attributes of Initial Blast on Mill Scale (Q3 & Q4) Attributes of Re-Blast (Q1 & Q2) Depth Micrometer 6.3 mils 6.8 mils Replica Tape 6.1 mils Peak Density 5/mm2 4/mm2 Peak Count 40/cm 37/cm Characteristic Yes No % Change Did re-blast decrease surface profile? X +7%1 & -3%2 Did re-blast change the peak density? -20% Did re-blast change the peak count? -8% 1Depth Micrometer 2Replica Tape
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Test Results Variable No. 6
Initial Peak Density (Quadrants 3 & 4) Peak Density Generated by Re-Blast (Quadrants 1 & 2)
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Conclusions Test Variables 1 and 2:
Shallow surface profile can be increased with a larger abrasive Shallow profile had no significant influence on: New profile depth Peak density or peak count
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Conclusions Test Variables 3 and 4:
Deep surface profile can be reduced with a smaller abrasive (reduction of 1 mil to > 3mils) Surface profile was deeper ( mils) than when smaller abrasive was used on mill scale Re-blast increased peak count & peak density (verses deep profile) Peak count & peak density both lower compared to use of “correct” (smaller) abrasive on mill scale
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Conclusions Test Variables 5 and 6: Prevention:
Deep surface profile cannot be reduced using the same abrasive (parallel re-blast) Re-blast reduced peak count & peak density Prevention: Prepare a test section (frequently required for cleanliness, but not roughness) Particularly beneficial if pre-existing profile is revealed; or severe pitting
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Conclusions Many factors potentially influence surface profile depth and other associated surface characteristics1 Blast Nozzle Type & Size No. of Blast Nozzles Abrasive Manufacturer Abrasive Type Abrasive Hardness Abrasive Shape Abrasive Size Blast hose length & diameter Compressor size (CFM) Air Pressure (PSI) Type of surface Hardness of surface Factors change from project to project. Extra time spent at project start-up can significantly reduce re-blast costs and impacts on schedule. 1Reference SSPC-PA 17, Appendix B
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10/10/2019 2:52 AM Too Deep or Too Shallow… Can Surface Profiles Be Changed by Additional Abrasive Blast Cleaning? Questions © 2007 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries. The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.
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