1、WORLDWIDEENGINEERINGSTANDARDSTest Procedure GMW15282Corrosion/Undercutting Scribe Creepback Copyright 2012 General Motors Company All Rights ReservedOctober 2012 Originating Department: North American Engineering Standards Page 1 of 71 ScopeNote: Nothing in this standard supercedes applicable laws a
2、nd regulations.Note: In the event of conflict between the English and domestic language, the English language shall takeprecedence.1.1 Purpose. This test method describes the procedure to be used for scribing previously coated (painted,plated, etc.,) specimens, removal of scribe line corrosion produ
3、cts and the measurement of the loss ofadhesion from the scribe line due to corrosive creepback.1.2 Foreword. Not applicable.1.3 Applicability. Evaluation of the adhesion properties of painted metal, plastic and sealer before and afterenvironmental testing.2 ReferencesNote: Only the latest approved s
4、tandards are applicable unless otherwise specified.2.1 External Standards/Specifications.ASTM D3330M2.2 GM Standards/Specifications.GMW148293 Resources3.1 Facilities.3.1.1 Air Supply. The air blow off equipment consists of an air supply capable of obtaining an open linepressure of 550 kPa through a
5、nozzle with a 3.0 mm round orifice. The length of the hose between the nozzleand the air regulator is recommended to be less than 3 m and the inside diameter of the hose between 6 mmand 10 mm.Note: If interval measurements are taken or the part is too large to allow for air blow off, it must be stat
6、ed inthe results documentation.3.2 Equipment.3.2.1 Scribe Tool. A straight-shank tungsten carbide tip, lathe cutting tool or carbide-tipped pencil type toolswith tip angle of 60 degrees 15 degrees or equivalent.3.2.2 Template. Any straightedge of sufficient length and thickness to guide the scribing
7、 tool in a straight linemay be used. The shank of the tool should follow the guide in order to ensure a uniform V cut. The carbide tipmust not come in contact with the guide.3.2.3 Continuity Tester. An electrical ohmmeter with needle tips should be used to ensure that based baremetal (electrically c
8、onductive) is exposed along each entire scribe line.3.2.4 Millimeter Scale (Ruler). Any scale (or ruler) with 1 mm divisions may be used. A transparent scale ishelpful for obtaining the measurements.3.2.5 Additional Equipment.3.2.5.1 Pressure Sensitive Adhesion Tape. Tape adhesively bonds to steel a
9、ccording to ASTM D3330M(refer to GMW14829 for detailed tape specifications).3.2.5.2 Application Device. Use a rubber eraser or equivalent device for applying tape.Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking per
10、mitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW15282 Copyright 2012 General Motors Company All Rights ReservedOctober 2012 Page 2 of 7Note: Appendix A contains photographs and information regarding typical equipment used.3.3 Test Vehicle/Test Piece. Not applicable.3.4 Test
11、 Time. Not applicable.3.5 Test Required Information. Not applicable.3.6 Personnel/Skills. Not applicable.4 Procedure4.1 Preparation.4.1.1 The scribe tool/tip should be inspected prior to use and replaced if any damage is observed. The scribetool/tip should be replaced if any inconsistencies in the s
12、cribe installation are observed.4.1.2 Prepare specimens for test by scribing in a direction that will allow the scribe line to be exposed in avertical direction unless otherwise specified. Hold the scribing tool at approximately 45 degrees to the surface.Position tool and scribe in such a manner tha
13、t the tip will make point contact resulting in a uniform V cut. Thescribe must penetrate all pre-treatment and coatings on the based bare metal leaving a uniform bright line.Avoid scribing near any edges. An electrical ohmmeter with needle tips should be used to ensure that basedbare metal (electric
14、ally conductive) is exposed along each entire scribe line.Note: If test panels have a hole on the upper area and the test panel cannot be placed in reverse direction(hole on the lower side), do not scribe the line directly under the hole. In this case, scribe the line a bit left orright to prevent c
15、orrosion from the hole edge that may influence the corrosion mechanism and creepbackbehavior.Note: Appendix B contains photographs and illustrations regarding proper scribe installation.4.2 Conditions.4.2.1 Environmental Conditions. Not applicable.4.2.2 Test Conditions. Deviations from the requireme
16、nts of this standard shall have been agreed upon. Suchrequirements shall be specified on component drawings, test certificates, reports, etc.4.3 Instructions.4.3.1 Sample Preparation.4.3.1.1 After testing of coated and scribed samples to corrosion environment, different phenomena mayappear around th
17、e scribe: delamination and corrosion. Both phenomena may also occur jointly. Careful samplepreparation must be done to detect both.4.3.1.2 Rinse the test sample with fresh water directly after the exposure to the load. Remove any remainingwater from the surface, if necessary, by compressed air (with
18、out scraping contact on the surface or otherwiseinjecting damage) and investigate the test sample for visible changes. If necessary, rinse the sample plateagain with fresh water from the tap.4.3.1.3 Dry specimens and dispense or cut a strip of tape off long enough to cover scribed area, being carefu
19、lnot to come in contact with anything before the test application.4.3.1.4 Press the tape down firmly on the surface with sufficient rubs of the eraser to remove air bubbles andto ensure good contact between the tape and paint surface.4.3.1.5 After 5 s to 10 s, hold the specimen not to move, and then
20、 grasp the tail end of the tape between thumband forefinger and pull upward with a rapid jerking motion perpendicular to the paint film.Note: For interim scribe creepback measurements, the sample should be rinsed with fresh water and driedusing compressed air or a soft towel or cloth so as not to da
21、mage the sample.Note: Based on different circumstances (e.g., availability of equipment on the workplace, base material of thesample, number of samples, sample size, etc.,) alternative and/or additional measures may have to be takento remove particles from the affected scribe area.4.3.2 Scribe Creep
22、back Measurement. Unless otherwise stated on the specification or drawing, evaluatescribe line creepback by measuring the distance between the unaffected paint surfaces on each side of thescribe line. The summation of the maximum left hand side creepback measurement and maximum right handside creepb
23、ack measurement is defined as the documented scribe creepback performance. This technique isreferred to as “zero to peak + zero to peak” and is illustrated in Appendix C.Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or network
24、ing permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW15282 Copyright 2012 General Motors Company All Rights ReservedOctober 2012 Page 3 of 75 Data5.1 Calculations. Scribe creepback measurement is illustrated in Appendix C.5.2 Interpretation of Results. Acceptance criteria
25、 shall be specified on the engineering drawing or in thematerial specification.5.3 Test Documentation. At a minimum, document maximum scribe creepback. In addition scribe creepbackmeasurements in standard increments along the scribe line may be taken in order to establish an individualsample average
26、. An example of scribe creepback evaluation and an example data documentation sheet isshown in Appendix D, Data Sheet D1.6 SafetyThis standard may involve hazardous materials, operations, and equipment. This standard does not propose toaddress all the safety problems associated with its use. It is t
27、he responsibility of the user of this standard toestablish appropriate safety and health practices and determine the applicability of regulatory limitations priorto use.An enclosed cabinet, a commercial glass peening cabinet, or a sandblasting cabinet with a viewing window,rubber gloves, foot switch
28、, dust collector, and magnetic sample hold are recommended for panels and smallparts.Parts too large for the cabinet described in the previous paragraph may be blown off outside the cabinet ifbarriers, baffles, or screens are provided to protect the operator and other individuals near the area where
29、 theair is being used. The guard that is used must be placed between the air nozzle and the operator.7 Notes7.1 Glossary. Not applicable.7.2 Acronyms, Abbreviations, and Symbols. Not applicable.8 Coding SystemThis standard shall be referenced in other documents, drawings, etc., as follows:Test to GM
30、W15282.9 Release and RevisionsThis standard was originated in March 2006. It was first approved by the Global Laboratory Corrosion TestingHarmonization Team in September 2006. It was first published in November 2006.Issue Publication Date Description (Organization)1 NOV 2006 Initial publication.2 SE
31、P 2011 Five year refresh of document. Modified paragraphs 3.4, 4.3, 8. Added new noteat 4.1, 4.3. (Corrosion Global Subsystem Leadership Team)3 OCT 2012 Added paragraph 4.1.1, previous 4.1 is now 4.1.2. (Corrosion Global SubsystemLeadership Team)Copyright General Motors Company Provided by IHS under
32、 license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW15282 Copyright 2012 General Motors Company All Rights ReservedOctober 2012 Page 4 of 7Appendix A: EquipmentFigure A1: Scribe Equipment Illustr
33、ationsTape and EraserMillimeter Scale (Ruler)Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW15282 Copyright 2012 General Motors Company
34、All Rights ReservedOctober 2012 Page 5 of 7Appendix B: Scribe InstallationFigure B1: Proper Scribe Installation with SchematicCopyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-G
35、M WORLDWIDE ENGINEERING STANDARDS GMW15282 Copyright 2012 General Motors Company All Rights ReservedOctober 2012 Page 6 of 7Appendix C: Scribe MeasurementsThe following process is used for measuring scribes:1. Scribe should be measured in millimeters using the “zero to peak + zero to peak” technique
36、 as illustratedin Figure C1 using the following formula:CMax = CLeft Max + CRight MaxFigure C1: Scribe Creepback Measurement Illustration2. The use of illuminated magnifiers is strongly encouraged. These can help overcome lightinginconsistencies and provide more accurate measurements.3. When a scrib
37、e exhibits no creepback, a zero (0) should be recorded.4. When a scribe exhibits immeasurable creepback (i.e., less than 1 mm, but greater than 0.0 mm) it shouldbe recorded as 0.5 mm.CLeft MaxCRight MaxCopyright General Motors Company Provided by IHS under license with General Motors CompanyNot for
38、ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW15282 Copyright 2012 General Motors Company All Rights ReservedOctober 2012 Page 7 of 7Appendix D: Example Scribe Creepback Evaluation and DocumentationExample: A scribe line 50 mm in len
39、gth after material specification test exposure.1. First, scribe should be measured in millimeters using the “zero to peak + zero to peak” technique asillustrated (refer to red line and text) in Figure D1.CMax = CLeft Max + CRight Max2. Second, scribe creepback should be measured across the scribe li
40、ne in 10 mm increments from the top ofthe scribe line as illustrated (refer to blue lines and text) in Figure D1.CAverage = (C10 mm + C20 mm + C30 mm+ C40 mm)/4Figure D1: Scribe Creepback Measurement IllustrationData Sheet D1: Sample Scribe CreepbackDate: Technician:Test Procedure: Exposure (time, c
41、ycles):GMW15282 Option (A or B): Results: (pass or fail):Procedure Requirement/Acceptance Criteria:CMax mm Comments:C10 mm mm Comments:C20 mm mm Comments:C30 mm mm Comments:C40 mm mm Comments:CAverage mm Comments:CLeft MaxCRight MaxC10 mm 10 mm 20 mmC20 mmC30 mmC40 mm30 mm40 mmCopyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
