1、Designation: D2803 09 (Reapproved 2015)Standard Guide for TestingFiliform Corrosion Resistance of Organic Coatings onMetal1This standard is issued under the fixed designation D2803; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, t
2、he year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope1.1 This guide covers thr
3、ee procedures for determining thesusceptibility of organic-coated metal substrates to formationof filiform corrosion.1.2 This guide is limited to the determination of whetherfiliform corrosion will occur between the organic coating andsubstrate.1.3 The values stated in SI units are to be regarded as
4、 thestandard. The values given in parentheses are for informationonly.1.4 This standard does not purport to address all of thesafety problems, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the
5、 applica-bility of regulatory limitations prior to use.NOTE 1Procedure B of this standard is equivalent to ISO 4623.2. Referenced Documents2.1 ASTM Standards:2B117 Practice for Operating Salt Spray (Fog) ApparatusD609 Practice for Preparation of Cold-Rolled Steel Panelsfor Testing Paint, Varnish, Co
6、nversion Coatings, andRelated Coating ProductsD823 Practices for Producing Films of Uniform Thicknessof Paint, Varnish, and Related Products on Test PanelsD1005 Test Method for Measurement of Dry-Film Thick-ness of Organic Coatings Using MicrometersD1654 Test Method for Evaluation of Painted or Coat
7、edSpecimens Subjected to Corrosive EnvironmentsD1730 Practices for Preparation of Aluminum andAluminum-Alloy Surfaces for PaintingD7091 Practice for Nondestructive Measurement of DryFilm Thickness of Nonmagnetic Coatings Applied toFerrous Metals and Nonmagnetic, Nonconductive Coat-ings Applied to No
8、n-Ferrous MetalsE104 Practice for Maintaining Constant Relative Humidityby Means of Aqueous Solutions2.2 International Standard:3ISO 46231 Paints and VarnishesDetermination of resis-tance to filiform corrosionPart 1: On steelISO 46232 Paints and VarnishesDetermination of resis-tance to filiform corr
9、osionPart 2: On aluminumISO 462810 Paints and VarnishesEvaluation of degrada-tion of coatingsDesignation of quantity and size ofdefects and of intensity of changesPart 10:Assessment offiliform corrosion3. Terminology3.1 Definitions:3.1.1 filiform corrosion, na special type of corrosion thatoccurs un
10、der coatings on metal substrates that is characterizedby a definite threadlike structure and directional growth.3.1.1.1 DiscussionFiliform corrosion usually occurs be-tween 20 and 35C (70 and 95F), with a correspondingrelative humidity range of 60 to 95 %; above 95 % humidity,blistering rather than
11、filiform corrosion may occur.4. Summary of Method4.1 Coated metal specimens are scribed and placed in acorrosive atmosphere to initiate corrosion. The specimens arethen exposed to controlled temperature and humidity condi-tions known to be conducive to filiform corrosion.4.2 In Procedure A, panels a
12、re subjected to a preliminaryexposure in the salt spray cabinet to initiate corrosion, rinsed,and placed in a humidity cabinet. In Procedure B, based on ISO4623, panels are either exposed to salt spray or dipped in a saltsolution but not rinsed before placing in the humidity cabinetoperated at a hig
13、her temperature than in Procedure A. In1This guide is under the jurisdiction of ASTM Committee D01 on Paint andRelated Coatings, Materials, and Applications and is the direct responsibility ofSubcommittee D01.27 on Accelerated Testing.Current edition approved June 1, 2015. Published June 2015. Origi
14、nallyapproved in 1969. Last previous addition approved in 2009 as D2803 09. DOI:10.1520/D2803-09R15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Do
15、cument Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, Wes
16、t Conshohocken, PA 19428-2959. United States1Procedure C, specimens are exposed as in Procedure A exceptthe humidity cabinet is operated at a higher temperature.4.3 The procedures contained in this guide differ signifi-cantly in method of initiation, and or temperature, or both, andhumidity of expos
17、ure and therefore may not yield comparableresults.5. Significance and Use5.1 Some organic coatings applied to metal substrates ex-hibit filiform corrosion when there is a break in the coating filmand the relative humidity is in the 70 to 95 % range.5.2 This guide can be used to determine the suscept
18、ibility oforganic coated metal substrates to the formation of filiformcorrosion.6. Apparatus6.1 Salt-Spray Chamber as described in Practice B117, forsalt-spray (fog) testing.NOTE 2The preferred initiator of corrosion at the scribe is the salt-fogatmosphere described in Practice B117. Exposure of the
19、 specimens for 2to4hinaclosed cabinet to the atmosphere above a 1 % acetic acidsolution is an acceptable alternative.6.2 Humidity CabinetAny cabinet with suitable tempera-ture and humidity controls with air circulation may be used.The size and detailed construction of the apparatus areoptional, prov
20、ided the conditions meet the requirements of thismethod.7. Test Specimen7.1 The composition, surface preparation, and number oftest specimens shall be agreed upon between the producer andthe user. Steel is the preferred substrate, but other metals suchas aluminum, copper magnesium, and stainless ste
21、el may beused. Zinc and zinc-coated steel are not recommended becausefiliform corrosion generally does not occur on zinc.NOTE 3Applicable test panel description and surface preparationmethods are given in Practice D609 and Practices D1730.7.2 Preparation of Test SpecimensThe method ofapplication, fi
22、lm thickness, curing, and conditioning shall beagreed upon between the producer and user.NOTE 4Practices D823 gives application methods that can be used toproduce films of uniform film thickness.NOTE 5Test Method D1005 and Practice D7091 give procedures thatcan be used for measurement of dry film th
23、ickness.7.3 Scribe the test specimen in accordance with Test MethodD1654 or as agreed upon between the producer and user.7.4 The back and edges of the panel should be protectedwith an anti-corrosion coating or tape, unless edge failure isbeing evaluated.8. Use of Control or Reference Materials8.1 Wh
24、en several coatings are being compared, select acoating as a control. Apply the control coating to the samesubstrate as the test coatings. For best results there should betwo controls, one known to perform well and one known toperform poorly.9. Procedure A9.1 Expose the test specimens to the salt-fo
25、g atmosphere inaccordance with Practice B117 for at least 4 h and not morethan 24 h, or as agreed upon between the producer and user.9.2 Remove from the salt-fog cabinet and thoroughly rinsewith distilled or demineralized water. Do not permit specimensto dry before placing in the humidity cabinet.9.
26、3 Place the specimens in the humidity cabinet so that theyare no closer together than 40 mm (1.5 in.) and not in contactwith any metal. Set the cabinet to operate at 25C (77F) and85 % relative humidity unless otherwise agreed upon betweenthe producer and user. The allowed operational limits are 62C(
27、63.5F) and 610 % relative humidity.NOTE 6The recommended means of maintaining the specified relativehumidity is to utilize trays of saturated potassium chromate solution (650g/L). Practice E104 describes other methods for maintaining relativehumidity, but they may affect the degree and rate of filif
28、orm corrosion.9.4 Inspect the specimens at intervals of approximately 168h for development of threadlike filaments from the scribe.Exercise care to maintain wetness of specimens duringinspection, since drying stops the original pattern of filiformcorrosion. New filiform may develop on continued expo
29、surebut at different points.9.4.1 Filiform corrosion will be noted as threadlike fila-ments (see Note 7), initiating at the scribe. A standard methodof rating failure due to filiform is not available. The uniformityof filament growth in direction, width, height and frequencyprecludes a precise ratin
30、g system. Photographs of filiformfailure are preferred for recording test results. Otherwise, abrief description of the filament growth and their frequency canbe made. ISO 462810 provides a method for the measurementof filiform filaments. Filiform corrosion may continue todevelop after specimens are
31、 removed from the humiditycabinet.NOTE 7The nature of grinding and grain direction on panels caninfluence the direction of filiform growth.9.5 The normal test period is 6 weeks (1008 h). Otherperiods may be used at the option of the producer and user.10. Procedure B (ISO 4623)10.1 Two alternative in
32、itiations of corrosion are available,based on initiation by dipping in sodium chloride solution (seeNote 8) or exposure to salt fog. The dipping technique isgenerally preferable for air drying and low-durability materi-als. For high-durability systems such as automotive finishesapplied to phosphated
33、 steel, the dipping technique may notproduce filiform corrosion and for these systems, it is prefer-able to adopt the salt-fog technique. In such cases, thenecessary period of exposure to salt fog depends on thedurability of the material under test but should rarely need toexceed 24 h.NOTE 8Sodium c
34、hloride 0.1 % (w/v) solution (for dipping technique)is prepared by dissolving1gofreagent grade sodium chloride (NaCl) in1 L of distilled or demineralized water. Place this solution in a vesselsuitable for complete immersion of the test panel.10.2 Dipping Technique:D2803 09 (2015)210.2.1 Immerse the
35、scribed specimen for 30 to 60 s in thesodium chloride solution (see Note 8).10.2.2 Take the specimen out of the solution and removeany drops of liquid adhering to it, taking care not to remove thesolution from the scribed marks.10.2.3 Place the specimen in a humidity cabinet set tooperate at 40C (10
36、4F) and 80 % relative humidity. Theallowed operational limits are 62C (63.5F) and 610 %relative humidity.10.2.4 Repeat the immersion procedure every 3 or 4 daysuntil the end of the test cycle (21 days) or as agreed uponbetween the producer and the user.10.3 Salt-Fog Technique:10.3.1 Expose the scrib
37、ed test specimen to the salt-fogatmosphere in accordance with Practice B117 for at least4hornot more than 24 h or as agreed upon between the producer andthe user.10.3.2 Remove the test specimen from the salt-fog cabinetand remove any drops of liquid adhering to it, taking care notto remove the solut
38、ion from the scribed marks.10.3.3 Place the specimen in a humidity cabinet set tooperate at 40C (104F) and 80 % relative humidity for thespecified period agreed upon between the producer and theuser. The allowed operational limits are 62C (63.5F) and610 % relative humidity.10.4 Follow the procedures
39、 in 9.4 and 9.4.1.11. Procedure C11.1 Expose the test specimens to the salt-fog atmospherein accordance with Practice B117 for at least 4 h and not morethan 24 h, or as agreed upon between the producer and user.11.2 Remove from the salt-fog cabinet and thoroughly rinsewith distilled or demineralized
40、 water. Do not permit specimensto dry before placing in the humidity cabinet.11.3 Place the specimens in the humidity cabinet so theyare no closer together than 1.5 in. (40 mm) and not in contactwith any metal. Set the cabinet to operate at 40C (104F) and80 % relative humidity. The allowed operation
41、al limits are62C (63.5F) and 610 % relative humidity.11.4 Follow the procedures in 9.4 and 9.4.1.12. Report12.1 The report shall include the following:12.1.1 Initiation procedure,12.1.2 Humidity cabinet operating temperature,12.1.3 Exposure period, and12.1.4 Rating of coatings as described in 9.4.1.
42、13. Keywords13.1 filiformASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infring
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