1、Designation: D2967 07 (Reapproved 2017)Standard Test Method forCorner Coverage of Powder Coatings1This standard is issued under the fixed designation D2967; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision.
2、 A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of the ratio ofcorner thickness (see 3.1.3) to face thickness (see 3.1.4)ofpowder coatings
3、 applied to a specific face thickness by dippingpreheated square bars into aerated powder and curing thecoating using predetermined conditions.NOTE 1The property of corner coverage has also been referred to as“edge coverage,” though the latter is not recommended. There arewidespread misunderstanding
4、s and expectations relative to the term “edgecoverage.” This test is performed on a steel bar having square corners andthe results do not necessarily relate to edges that are sharper, that is, burrs.A coating that has measurable corner coverage may still not protectsharper edges from corrosion or pr
5、ovide the electrical insulation needed insome applications.1.2 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is ther
6、esponsibility 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.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization establi
7、shed in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D374/D374M Test Methods for Thickness of Solid Electri-cal Insula
8、tion3. Terminology3.1 Definitions:3.1.1 coating powders, nfinely divided particles of resin,either thermoplastic or thermosetting, generally incorporatingpigments, fillers, and additives and remaining finely dividedduring storage under suitable conditions, which, after fusingand possibly curing, giv
9、e a continuous film.3.1.1.1 DiscussionThe coating powder may containfillers, colorants, curing agents, etc., consistent with producingthe desired coatings. The powder is applied by various methodssuch as spraying, sprinkling, or dipping. Usually hot parts areused. Heat causes the powder to melt and
10、flow into a densecoating.3.1.2 corner coverage, nof powder coating, the ratio ofthe corner thickness to the face thickness of the fused coatingexpressed in percent.3.1.3 corner thickness, nof powder coating, the averagethickness of the coating on sharp 90 corners of steel barsmeasured at 45 to the f
11、lat surfaces.3.1.4 face thickness, nof powder coating, the averagethickness of the coating on flat surfaces of steel bars measuredperpendicular to the surfaces.3.1.5 powder coatings, ncoatings which are protective ordecorative, or both, formed by the application of a coatingpowder to a substrate and
12、 fused in a continuous film by theapplication of heat or radiant energy.4. Significance and Use4.1 This test method measures the degree to which differentcoating powder materials cover sharp corners. Corner coverageis influenced by face thickness, thixotropy, melt viscosity,surface tension, cure rat
13、e, and temperature of application andcuring.5. Apparatus5.1 Aerated BedSuitable for providing a uniformly sus-pended dense phase of freemoving powder. Fig. 1 shows aschematic of an aerated bed used for suspending the coatingpowder. The equipment consists of an open top chamber whichhas a porous plat
14、e for a false bottom. Air is introduced underthe plate at a low pressure so that it filters through the porousplate and uniformly suspends the particles contained in thechamber.1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, Materials, and Applications
15、 and is the direct responsibility ofSubcommittee D01.51 on Powder Coatings.Current edition approved June 1, 2017. Published June 2017. Originallyapproved in 1971. Last previous edition approved in 2013 as D2967 07 (2013).DOI: 10.1520/D2967-07R17.2For referenced ASTM standards, visit the ASTM website
16、, www.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.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesTh
17、is international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (
18、TBT) Committee.15.2 Micrometer Caliper25.4 mm (1 in.), in accordancewith Method C of Test Methods D374/D374M.5.3 Oven, with forced convection capable of maintainingthe specified temperature within 63C.5.4 Test Bars, four, measuring 13 by 13 by 100 mm (12 by12 by 4 in.) in accordance with Fig. 2.5.4.
19、1 Use bars that are free of rust and dirt, and which havebeen washed with a clean solvent to remove any traces of oilysubstances. Bars may be reused if the coating used in aprevious test has been completely removed without marring thesurfaces or corners of the bars. Appropriate methods ofremoval inc
20、lude the use of stripping solutions, heat, and carefulscraping with a sharp blade, or combinations thereof.6. Sampling6.1 The powder sample shall be from one lot and berepresentative of the lot.7. Test Specimens7.1 The test specimens shall be the steel bars in accordancewith 5.4, coated with powder
21、to form a smooth, continuouscoating of the specified thickness.8. Procedure8.1 Measure and record the distance across both flat sur-faces and both diagonals (A, B, C, and D, Fig. 2) of the fourtests bars to the nearest 0.0025 mm (0.0001 in.) at a point 38mm (112 in.) from the bottom of the bars at 2
22、3 6 1C inaccordance with Method C of Test Methods D374/D374M.8.2 Preheat the four test bars by hanging them in the ovenwith a wire through the hole in the bar. Heat at the prescribedtemperature for 30 min, or until the bars are at the desiredtemperature (as agreed upon between the purchaser and sell
23、er).8.3 Fill the bed with fresh, dry coating powder to provide adepth of at least 152 mm (6 in.) of aerated powder. Aeratepowder at a rate providing a constant dense phase behaving asa liquid with a minimum of geysering.8.4 Remove the hot bars from the oven one at a time, and 4612 s after removal ra
24、pidly insert them in the aerated powderfor the time required to obtain the specified face thickness.NOTE 2Coating powder materials may have a wide range of charac-teristics and end uses; thus the thickness and coating conditions used mustbe mutually agreed upon by the supplier and consumer. Submersi
25、on timedepends on thickness desired, preheat temperature, and material charac-teristics.8.5 Cure the coated bars at the prescribed time and tempera-ture.8.6 Cool the bars to 23 6 1C.8.7 Repeat 8.1 using the coated bars.9. Calculation9.1 Average the distance measurements across the two flatsurfaces A
26、 and B and also the two diagonals C and D. Subtractthe average measurements of the uncoated bar from those ofthe coated bar and divide by 2 to obtain the average facethickness and average corner thickness.9.2 Calculate the percent corner coverage for each bar asfollows:% Corner coverage 5avg corner
27、thicknessavg face thickness3100 (1)9.3 Calculate the average corner coverage.9.4 The corner coverage of three of the four bars must agreewithin 65 %. If not, discard all results and prepare newspecimens. Include measurements of all four bars in thecalculations.FIG. 1 Aerated Bed(in.) mm (in.) mm18 3
28、.212 12.714 6.4 4 102NOTE 1AISI 52100 steel hardened to Rockwell C55 to C60 andground square to within 0.025 mm (0.001 in.) with sharp (no measurableradius) corners. 813 nm (32 in.) finish on four long sides. Drawingdimensions are in inches.FIG. 2 Corner Coverage Test BarD2967 07 (2017)210. Report10
29、.1 Report the following information:10.1.1 Powder designation,10.1.2 Preheat temperature, in degrees Celsius,10.1.3 Cure time and temperature,10.1.4 Face thickness mm (in.),10.1.5 Calculated corner coverage to the nearest integer.11. Precision and Bias11.1 The precision of this test method has not b
30、een deter-mined.NOTE 3Operators familiar with this test method estimate that thevariation of means of observations within a single laboratory is notexpected to exceed 10 % of reported value when the result exceeds 35 %.For lower corner coverage values more erratic results may be obtained.11.2 This t
31、est method has no bias because the value ofcorner coverage is defined solely in terms of this test method.12. Keywords12.1 coating powder; corner coverage; corner thickness;edge coverage; face thickness; powder coatingASTM International takes no position respecting the validity of any patent rights
32、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 infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any tim
33、e by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will r
34、eceive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM I
35、nternational, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ 07 (2017)3
