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Investigating Failure: Security Barrier with Compromised Corrosion Protection
Welcome Speaker: Robert Ikenberry, California Engineering Contractors Organizers: Larson Electronics and JPCL Welcome Speaker: Rob Lanterman, KTA-Tator, Inc. Moderator: Josiah Lockley, Paintsquare Organizers: Paintsquare
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Investigating Failure: Security Barrier with Compromised Corrosion Protection
Agenda Rob Lanterman, KTA-Tator, Inc (45 minutes) Questions and answers (about 10 minutes)
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Recording Investigating Failure: Security Barrier with Compromised Corrosion Protection Recording and Reference This presentation is being recorded, and will be available soon by visiting Copy of reference slides will also be available for download
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Recording Recording Investigating Failure: Security Barrier with Compromised Corrosion Protection Today’s Speaker Rob Lanterman Coatings Consultant, KTA-Tator, Inc. A coatings consultant with KTA-Tator Inc. He is an SSPC Certified Protective Coatings Specialist and a NACE Level 2 Certified Coatings Inspector with over 10 years of coatings engineering experience
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Presented by: Jayson L. Helsel, PE, PCS KTA-Tator, Inc.
investigating FAILURE: Security barrier with compromised corrosion protection Presented by: Jayson L. Helsel, PE, PCS KTA-Tator, Inc.
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Learning Objectives Comprehension of the webinar will enable the participant to: Understand the typical steps for conducting a coating failure investigation Describe some typical field coating tests or measurements when investigating a coating failure List some typical types of lab testing used for analyzing coating samples Understand the primary cause of the security fence failure
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BACKGROUND Security barrier was installed at electrical power station
Coating was failing after several months Facility within view of residential area
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COATING FAILURE INVESTIGATION
Data collection Field investigation Laboratory analysis Review, conclusions and report
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Data Collection Specification Construction sequence Structure history
Painting history
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Specification Surface preparation Coating materials Film thicknesses
Method of application Product data sheets
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Construction Sequence
Which components were erected first? Which components were erected last? How much time lapsed between the beginning and the end of a project?
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Structure History How long has the existing system been in place? Have there been other failures? Were failures isolated or widespread?
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Painting History Was the system or primer applied in the shop?
Was the finish coat or entire system applied in the field?
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Data collection Barrier constructed of galvanized sheet formed in corrugated shape Perimeter barrier was roughly rectangular
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Data collection Primary surface preparation was degreasing
Powder coating applied in fluidized bed process (i.e. shop applied) Low density polyethylene (LDPE) Field touch-up with acrylic primer/finish
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Data collection Barrier installed in late fall
Coating failure reported in following spring Failure worsened over year
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Field investigation Patterns of failure (visual exam)
Coating thickness Adhesion Substrate condition Sample collection
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Looking for Patterns Is the system failing everywhere or in a single, isolated location? Directional exposure differences, e.g. south facing sun exposure
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Looking for Patterns Failure/delamination from substrate along vertical edges Cut edges in majority of cases Field touch-up but poor coverage Often at inward bends Sometimes at vent openings Occurred on both sides, all exposures
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Coating Thickness Gages for Different Surfaces
Gages to measure thickness on ferrous and non-ferrous metal surfaces Micrometer measures thickness on disbonded coating chips Tooke gage measures thickness by observation into the coating system
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Dry Film Thickness Gages
Measuring over ferrous metal (Magnetic pull-off or magnetic flux) Measuring over non-ferrous metals like aluminum and copper (eddy current) Measuring over non-ferrous, non-metallic surfaces like concrete and wood (ultrasound)
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Electronic/magnetic DFT gage
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Micrometer
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Tooke Gage
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Coating thickness Electronic gage measured 10 to 55 mils
Typical range 12 to 25 mils Thickness varied along panel Low end typically 12 to 15 mils High end typically 22 to 25 mils Higher thickness often at cut edge
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Measuring Adhesion ASTM D3359 – Tape test ASTM D6677 – Knife adhesion
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Measuring Adhesion by Tape Test
ASTM D3359 Method A - The “X” cut (>5 mils) Method B - The “Cross-Cut” (< 5 mils)
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Evaluating the X-Cut 5A No peeling or removal
4A Trace peeling along incisions 3A Jagged removal along incisions up to /16” on either side 2A Jagged removal along most of incisions up to 1/8” on either side 1A Removal from most of the area of the X under the tape 0A Removal beyond the area of the X
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Measuring Adhesion by knife
ASTM D6677 “X” cut Probe cut with knife to remove coating
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Evaluating knife Cut 10 Coating extremely difficult to remove
Fragments no larger than 1⁄32” by 1⁄32” removed with great difficulty 8 Coating difficult to remove Chips from 1⁄16” by 1⁄16” to 1⁄8” by 1⁄8” removed with difficulty
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Evaluating knife Cut 6 Coating somewhat difficult to remove
Chips from 1⁄8” by 1⁄8” to 1⁄4” by 1⁄4” removed with slight difficulty 4 Coating somewhat difficult to remove Chips in excess of 1⁄4” by 1⁄4” removed by exerting light pressure with the knife blade
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Evaluating knife Cut 2 Coating easily removed
Once started with knife blade coating can be grasped with ones fingers and easily peeled to a length of at least 1⁄4” 0 Coating easily peeled to length >¼”
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knife Cut ADHESION 0 rating and poor adhesion near failing areas
4 to 6 rating and fair adhesion for intact coating when thickness was greater (e.g. 20 mils) 8 rating and good adhesion for intact coating when thickness was lower (e.g. 12 mils)
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Substrate Condition Remove coating
Determine presence of mill scale, rust or contamination Level of surface preparation (power tool cleaning, blast cleaning, etc.)
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Substrate Condition No evidence of contamination
Galvanized surface was smooth, no roughening obvious
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Sample Collection Coating chips Corrosion samples Blister liquid/caps
Failing & non-failing areas Corrosion samples Blister liquid/caps Coating retains
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Laboratory Analysis Optical microscopy Infrared Spectroscopy
Pyrolysis/Gas Chromatography/Mass Spectroscopy SEM/EDS
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Optical Microscopy Visual examination of coating samples
Cameras attached to the microscope May direct or alter the course of a failure investigation
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Fourier Transform Infrared Spectroscopy
Produces a fingerprint of coating Can determine if coating specified was the one actually applied
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Pyrolysis/Gas Chromatography/ Mass Spectroscopy
Detects presence of solvents trapped in a coating or in blister liquid
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Scanning Electron Spectroscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDS)
Uses magnification up to 10,000x Examines defects in the coating surface Compares failing and non-failing areas Provides an elemental analysis of the surface
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Holiday Detection Two types:
Low voltage (wetted sponge) – coatings that are less than 20 mils thick High voltage (spark testers) – coatings that are greater than 20 mils thick
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Pinholes and Holidays Holidays – skips or misses in the coating/lining system Pinholes – tiny voids in the coating or lining Testing found many holidays
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conclusions 80% of failure at cut ends of panels – allowed moisture to travel beneath coating Significant thickness variation – 12 to 25 mils Poorer adhesion at high thickness Failure at ends typically at higher thickness Numerous holidays at edges and openings
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Repair RECOMMENDATIONS
Remove poorly adhered coating Abrade/sand existing intact coating and exposed galvanizing Apply acrylic primer and 1 or 2 acrylic finish coats Consider an elastomeric acrylic coating
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other RECOMMENDATIONS
Simpler barrier design Better galvanizing surface prep Chemical cleaning Phosphate conversion coating Evaluate/improve application process to achieve uniform thickness Better field touch-up
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Coating failure investigation
Questions?
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Recording Recording Investigating Failure: Security Barrier with Compromised Corrosion Protection Recording and Reference This presentation has been recorded, and will be available soon by visiting paintsquare.com/webinars Copy of reference slides available for download
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