1、Designation: D 4138 07aStandard Practices forMeasurement of Dry Film Thickness of Protective CoatingSystems by Destructive, Cross-Sectioning Means1This standard is issued under the fixed designation D 4138; the number immediately following the designation indicates the year oforiginal adoption or, i
2、n the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This practice describes the measurement of dry filmthickness of coating films by
3、 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 includes definitions
4、 of key terms, reference docu-ments, 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 Procedure BUsing
5、 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 process. The sur
6、face 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 theseprocedure
7、s.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 purport to ad
8、dress 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:2D 823 Practi
9、ces for Producing Films of Uniform Thicknessof Paint, Varnish, and Related Products on Test PanelsD 1005 Test Method for Measurement of Dry-Film Thick-ness of Organic Coatings Using MicrometersD 7091 Practice for Nondestructive Measurement of DryFilm Thickness of Nonmagnetic Coatings Applied toFerro
10、us 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 thickness o
11、f 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 reticle, na sca
12、le 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 in thecoa
13、ting through a microscope having a built-in reticle with ascale. Each procedure employs different instruments to makethe cut in the coating.4.2 Procedure AUses a carbide or carbide-tipped wedgeto cut a groove in the coating. The groove is cut at a preciseangle to the surface. Various wedge angles ar
14、e available. Thisprocedure requires the manual cutting of the coating bydragging a cutting wedge through both the coating and the1This practice is under the jurisdiction of ASTM Committee D01 on Paint andRelated Coatings, Materials, and Applications and is the direct responsibility ofSubcommittee D0
15、1.23 on Physical Properties of Applied Paint Films.Current edition approved July 1, 2007. Published July 2007. Originally approvedin 1982. Last previous edition approved in 2007 as D 4138 07.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serv
16、iceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, Uni
17、ted States.surface 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 avoided. On wood or other directional m
18、aterial,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 angles ofinclination to the surface. This
19、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 clean, non-tearing, controlled disinteg
20、ration 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 commonly usedfor hard, brittle or very thin
21、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 cutting.Some plastic coatings may stretch. O
22、ther 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, improvedcuts can be achieved by wetting
23、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 differentoperators, it is essential to measure fil
24、m 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 thickness tolerances in order that they
25、 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 coating thickness.6.2 If multiple coat
26、s 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. Coating shall be uniformly applied in
27、 accordancewith Practice D 823 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 D 1005 orPractice D 7091.PROCEDURE A GROOVE CUTTING INSTRUME
28、NTS7. 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 films of known thickness (see Test Meth
29、odD 1005).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 nominally designated 13,23, and 103 t
30、o 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 surface fora precisely aligned incisi
31、on.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 surface approximately 50 mm (2 in
32、.)long where the thickness measurement will be made.8.3 Select a cutting tip based on estimated film thickness. Ifthickness is unknown, make a trial determination with a 23 tip.FIG. 1 Geometry of Thickness Measurement FIG. 2 Grooves Made by 13,23, and 103 Cutting TipsD 4138 07a28.4 Draw the cutting
33、tool across the 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
34、parallel to the 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 u
35、pper edge of the 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 INSTRUM
36、ENTS9. Apparatus9.1 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 wit
37、h the coated surface 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 (1
38、4 in.)wide by 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 in23 position.10.4 Install the grinding bit so that it extends from the chuckmouth.10.5 The
39、 cut is made by 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 supp
40、orts (see Fig. 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 illuminatedmicros
41、cope. Fig. 6 depicts 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 ass
42、ociatedwith each. The sum of the reticle graduations shall be multi-plied by the appropriate conversion factor for the instrumentangle position used.FIG. 3 Typical View Through Microscope Showing ReticleD 4138 07a3FIG. 4 Holding Rotary Tool for GrindingFIG. 5 Rotary Tool BlockPositions for Various C
43、utting Angles(Slopes)D 4138 07a4PROCEDURE C DRILLING INSTRUMENTS11. Apparatus11.1 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 bi
44、t to penetrate through thecoating system down to the substrate.11.4 MicroscopeA microscope, typically of 50+ magnifi-cation, with scaled divisions showing through reticle.12. Procedure12.1 Select a test panel or choose a site for thicknessmeasurement.12.2 Using an appropriate surface marker of contr
45、astingcolor, mark a surface area 6 by 6 mm (14 by14 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 sel
46、ected. Tighten therecess socket-head screw.12.5 Place 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
47、inrecess) until the cutter has penetrated the coating 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 indivi
48、dual layers ofpaint as shown in Fig. 7.12.9 To calculate 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
49、 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, andNOTE 1The coating thickness is determined using the graduationsalong the long axis of the cut represented by the A and B dimensions inthis drawing.FIG. 6 Typical View Through Microscope of Rotary Tool CutFIG. 7 Typical View Through Microscope of Cutter/Drill CutD 4138 07a513.1.6 Gage operators n
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