1、Designation: D4138 07a (Reapproved 2013)Standard Practices forMeasurement of Dry Film Thickness of Protective CoatingSystems by Destructive, Cross-Sectioning Means1This standard is issued under the fixed designation D4138; the number immediately following the designation indicates the year oforigina
2、l adoption or, in the case of revision, the 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.1. Scope*1.1 This practice describes the measurement of dry filmthickness of c
3、oating films by microscopic observation ofprecision angular cuts in the coating film. Use of theseprocedures may require repair of the coating film. This practiceis intended to supplement the manufacturers instructions forthe manual operation of the gages and is not intended to replacethem. It inclu
4、des definitions of key terms, referencedocuments, the significance and use of the practice, and theadvantages and limitations of the instruments.1.2 Three procedures are provided for measuring dry filmthickness of protective coating systems:1.2.1 Procedure AUsing groove cutting instruments.1.2.2 Pro
5、cedure BUsing grinding instruments.1.2.3 Procedure CUsing drill bit instruments.1.3 These procedures are not applicable for soft or ductilesubstrates that may deform under the test gage cutting tip. Thesubstrate should be sufficiently rigid to prevent deformation ofthe coating during the cutting pro
6、cess. The surface may be flator moderately curved. Pipes as small as 25 mm (1 in.) indiameter may be measured in the axial direction.1.4 Individual coats in a multicoat system where there is adiscernible visual difference between coats or the overallthickness of a coating system can be measured by t
7、heseprocedures.1.5 The range of thickness measurement is typically 2 to2000 microns (0.1 to 80 mils) and depends upon the cuttingangle of the blade.1.6 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.7 This standard does not
8、purport to address all of thesafety concerns, 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 applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:
9、2D823 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 MicrometersD7091 Practice for Nondestructive Measurement of DryFilm Thickness of Nonmagnetic Coatings Appli
10、ed toFerrous Metals and Nonmagnetic, Nonconductive Coat-ings Applied to Non-Ferrous Metals3. Terminology3.1 Definitions of Terms:3.1.1 accuracy, nthe measure of the magnitude of errorbetween the result of a measurement and the true thickness ofthe item being measured.3.1.2 dry film thickness, nthe t
11、hickness of a coating (orcoating layers) as measured from the surface of the substrate.3.1.3 micrometre (micron), none one-thousandths of amillimetre (0.001 mm); 25.4 microns = 1 mil.3.1.4 mil, nan imperial unit of measure; one one-thousandths of an inch (0.001 in.); 1 mil = 25.4 microns.3.1.5 retic
12、le, na scale on transparent material fitted at thefocal plane of the eyepiece of the microscope for the purposeof measuring the width of a feature within the image.4. Summary of Practice4.1 The three procedures are based on measurement of dryfilm thickness by observation of the width of angular cuts
13、 in thecoating through a microscope having a built-in reticle with ascale. Each procedure employs different instruments to makethe cut in the coating.1These practices are under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, Materials, and Applications and are the direct respons
14、ibilityof Subcommittee D01.23 on Physical Properties of Applied Paint Films.Current edition approved July 1, 2013. Published July 2013. Originally approvedin 1982. Last previous edition approved in 2007 as D4138 07a. DOI: 10.1520/D4138-07AR13.2For referenced ASTM standards, visit the ASTM website, w
15、ww.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive,
16、PO Box C700, West Conshohocken, PA 19428-2959. United States14.2 Procedure AUses a carbide or carbide-tipped wedge tocut a groove in the coating. The groove is cut at a precise angleto the surface. Various wedge angles are available. Thisprocedure requires the manual cutting of the coating bydraggin
17、g a cutting wedge through both the coating and thesurface of the substrate. In this operation, the cutter trailsmidway between the two guide studs. Continuous 3pointsurface contact should be maintained to assure precise verticalalignment of the groove. Excessive pressure on the guide studsshould be
18、avoided. On wood or other directional material,incisions should be made in the grain or “machine” direction toavoid ragged cuts.4.3 Procedure BUses a high speed rotary grinding disk ordrum type bit to cut partial cylindrical cavities in the coating.Axes of the cavities can be oriented at various ang
19、les ofinclination to the surface. This procedure is similar to Proce-dureAexcept in how the cut is made.This technique eliminatesthe deformations of coating and substrate that may occur whenconventional cutting wedges are used. Hard, brittle, tough,fibrous, tender, or elastomeric materials exhibit c
20、lean, non-tearing, controlled disintegration under the rotary cutter. Thehigh-speed “erodes” away surface material in a precise pattern,leaving adjacent and underlying areas undisturbed.4.4 Procedure CUses a specific angle tip drill bit to cut aconical cavity in the coating. This procedure is common
21、ly usedfor hard, brittle or very thin coatings. Less damage often resultsfrom the small hole used to measure thickness.4.5 All procedures involve cutting through the coating. Thecutting operation works better on some coatings than on others.For example, elastomeric coatings may close up after cuttin
22、g.Some plastic coatings may stretch. Other coatings may tear.The cutting process must result in a clearly visible cross-section of the coating or coating system and the substrate. Softor elastic materials can sometimes be cooled or frozen to obtaingood cutting characteristics. With some coatings, im
23、provedcuts can be achieved by wetting the surface, or by speeding orslowing the cutting rate.5. Significance and Use5.1 Many coating properties are markedly affected by thefilm thickness of the dry film such as adhesion, flexibility, andharness. To be able to compare results obtained by differentope
24、rators, it is essential to measure film thickness carefully.5.2 Most protective and high performance coatings areapplied to meet a requirement or a specification for the dry-filmthickness of each coat, or for the complete system, or both.Coatings must be applied within a certain minimum andmaximum t
25、hickness tolerances in order that they can fulfilltheir intended function.6. Test Specimen6.1 The test specimen can be the coated structure orcomponent/part on which the thickness is to be evaluated, orcan be test panels of similar material and surface roughness onwhich it is desired to measure the
26、coating thickness.6.2 If multiple coats of paint are to be measured, successivecontiguous coats should be of contrasting colors to aid sharpdiscrimination of interfaces.6.3 For test panels, if measurement repeatability is desiredfor a particular paint system, care shall be taken in panelpreparation.
27、 Coating shall be uniformly applied in accordancewith Practice D823 or as agreed upon between the contractingparties. Panels shall be placed in a horizontal position duringdrying. Uniform application thickness shall be verified byanother measurement method such as Test Method D1005 orPractice D7091.
28、PROCEDURE A GROOVE CUTTING INSTRUMENTS7. Apparatus7.1 Scribe Cutter and an Illuminated Microscope withMeasuring Reticle. The scribe cutter and illuminated micro-scope may be combined as a single instrument. Verification ofinstrument accuracy shall be performed by taking measure-ments on applied film
29、s of known thickness (see Test MethodD1005).7.2 Cutting Tips shall be designed to provide a very smoothincision in the paint film at a precise angle to the surface (seeFig. 1). Separate tip designs (angles) shall provide cuts ofknown slopes such as 1 to 1, 1 to 2, and 1 to 10. These tips shallbe nom
30、inally designated 1, 2, and 10 to indicate the ratioof the lateral measurement to vertical depth (see Fig. 2). Thelateral measurement is represented by the reticle markings andthe vertical depth is represented by the coating film thickness.Ensure that the tip aligns vertically with the painted surfa
31、ce fora precisely aligned incision.7.3 Illuminated Microscope typically of 50+ magnification,shall contain a scaled reticle (see Fig. 3).8. Procedure8.1 Select a test panel or choose a site for the thicknessmeasurement.8.2 Using an appropriate surface marker of contrastingcolor, mark a line on the s
32、urface approximately 50 mm (2 in.)long where the thickness measurement will be made.FIG. 1 Geometry of Thickness MeasurementD4138 07a (2013)28.3 Select a cutting tip based on estimated film thickness. Ifthickness is unknown, make a trial determination with a 2 tip.8.4 Draw the cutting tool across th
33、e paint film toward thebody and increase pressure on the cutting tip until it barely cutsinto the substrate before it crosses the marked line.8.5 Take readings at the intersection of the marked line andincision. Align the scale at right angles to the cut so that thescale divisions are parallel to th
34、e cut. Read by measuring on thereticle the distance from the substrate/coating demarcation upthe longer machined slope of the incision to the upper cut edgeof each respective coating layer of the coating system. Makesure that the smooth cut face of the groove is measured. Themachined upper edge of t
35、he cutting tip usually leaves a lessjagged cut. If multiple coats are observed, individual thick-nesses of each coat may be read. The actual coating thicknessis derived by multiplying the reticle reading by the conversionfactor for the respective cutting tipPROCEDURE B GRINDING INSTRUMENTS9. Apparat
36、us9.1 Rotary ToolA cordless high speed (5000 to 10 000r/m) rotary grinder.9.2 Grinding BitTungsten carbide cylindrical-shapedgrinding bit placed in a chuck of the rotary tool for grindingthrough the coating system.9.3 Positioning BlockThe positioning block provides spe-cific angles with the coated s
37、urface for the rotary tool to grindthrough the coating system.9.4 Illuminated MicroscopeSee 7.3.10. Procedure10.1 Select a test panel or choose a site for thicknessmeasurement.10.2 Using an appropriate surface marker of contrastingcolor, mark a line on the surface approximately 6 mm (14 in.)wide by
38、approximately 25 mm (1 in.) long where the thicknessmeasurement will be made.10.3 Select a grinding position based on estimated coatingsystem. If thickness is unknown, make a trial determination in2 position.10.4 Install the grinding bit so that it extends from the chuckmouth.10.5 The cut is made by
39、 grinding a groove through thecoating system down to the substrate. Take care to hold theinstrument at the predetermined angle with sufficient firmnessto prevent sideways movement, as shown in Fig. 4.10.6 Grinding slopes or positions are accomplished by usingthe position block or supports (see Fig.
40、5).10.7 Ground area will appear as partial cylindrical cavity,with the cavity wall angling gradually upward from thesubstrate to the coating systems exterior surface.10.8 Thickness of each coating system layer of any combi-nation of layers may be determined using the illuminatedmicroscope. Fig. 6 de
41、picts the groove that results from grindingthrough a coating system. The coating thickness is determinedusing the graduations along the long axis of the cut representedby theAand B dimensions in this drawing. Note that the sketchdepicts successive coats and the reticle graduations associatedwith eac
42、h. The sum of the reticle graduations shall be multi-plied by the appropriate conversion factor for the instrumentangle position used.FIG. 2 Grooves Made by 1, 2, and 10 Cutting TipsFIG. 3 Typical View Through Microscope Showing ReticleD4138 07a (2013)3PROCEDURE C DRILLING INSTRUMENTS11. Apparatus11
43、.1 Cutter/Drill BodyAn implement to hold the drill bitin place over the coating system surface.11.2 HandwheelsLight and heavy hand wheels for hold-ing the cutter/drill in place and turning.11.3 Cutter/DrillCutter/drill bit to penetrate through thecoating system down to the substrate.11.4 MicroscopeA
44、 microscope, typically of 50+magnification, with scaled divisions showing through reticle.FIG. 4 Holding Rotary Tool for GrindingFIG. 5 Rotary Tool BlockPositions for Various Cutting Angles(Slopes)NOTE 1The coating thickness is determined using the graduations along the long axis of the cut represen
45、ted by the A and B dimensions in thisdrawing.FIG. 6 Typical View Through Microscope of Rotary Tool CutD4138 07a (2013)412. Procedure12.1 Select a test panel or choose a site for thicknessmeasurement.12.2 Using an appropriate surface marker of contrastingcolor, mark a surface area 6 by 6 mm (14 by14
46、in.) where thethickness measurement will be made.12.3 Select the appropriate handwheel. Use the heavy wheelon hard or thick coatings above 250 microns (10 mils) and lightwheel for soft or thinner coatings.12.4 Insert the cutter in the handwheel selected. Tighten therecess socket-head screw.12.5 Plac
47、e the drill body on the surface to be measured withthe hole directly above the measurement area. Fit the cutterinto the drill hole.12.6 Rotate the handwheel in a clockwise direction, usingpressure as necessary (for soft coatings rotate with finger inrecess) until the cutter has penetrated the coatin
48、g and markedthe substrate.12.7 Remove the cutter assembly and the drill body. Viewthe cut hole with the microscope, focusing on the side of thehole.12.8 Note the number of reticle divisions between thecoating surface and the substrate or the individual layers ofpaint as shown in Fig. 7.12.9 To calcu
49、late the coating thickness, multiply gradationsby 20 for microns and by 0.79 for mils.13. Report13.1 The following items should be reported:13.1.1 Gage type (manufacturer, model and serial no.),13.1.2 Size of cutting tip or grinding bit used,13.1.3 Method of accuracy verification (if appropriate),13.1.4 Results of a thickness determination,13.1.5 If more than one measurement is made and specificresults for each location are not needed, report the minimum,the maximum, and the average thickness, and13.1.6 Gage operators name.14. Keywords14
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