1、Designation: D 2967 07Standard Test Method forCorner Coverage of Powder Coatings1This standard is issued under the fixed designation D 2967; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in par
2、entheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method covers the determination of the ratio ofcorner thickness (see 3.1.3) to face thickness (see 3.1.4)ofpowder coatings applied to a
3、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 misunderstandings and expectat
4、ions 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 provide the elec
5、trical 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 theresponsibility
6、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 374 Test Methods for Thickness of Solid Electrical Insu-lation3. Terminology3.1 Definitions:3.1.1 co
7、ating powders, n finely 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, give a continuous film.3.1.1.1 DiscussionThe
8、 coating powder may contain fill-ers, colorants, curing agents, etc., consistent with producing thedesired coatings. The powder is applied by various methodssuch as spraying, sprinkling, or dipping. Usually hot parts areused. Heat causes the powder to melt and flow into a densecoating.3.1.2 corner c
9、overage, 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 flat surfaces.3.1.4 face thickness, nof
10、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 fused in a continuous film by theappli
11、cation 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 rate, and temperature of application andcu
12、ring.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 plate for a false bottom. Air is introduced
13、 underthe plate at a low pressure so that it filters through the porousplate and uniformly suspends the particles contained in thechamber.5.2 Micrometer Caliper25.4 mm (1 in.), in accordancewith Method C of Test Methods D 374.5.3 Oven, with forced convection capable of maintainingthe specified tempe
14、rature within 63C.1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, Materials, and Applications and is the direct responsibility ofSubcommittee D01.51 on Powder Coatings.Current edition approved June 1, 2007. Published June 2007. Originallyapproved in 19
15、71. Last previous edition approved in 2002 as D 2967 02a.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 Document Summary page onthe ASTM website.1*A
16、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, United States.5.4 Test Bars, four, measuring 13 by 13 by 100 mm (12 by12 by 4 in.) in accordance with Fig. 2.5.4.1 Use bars that are free
17、 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 include the use of strippin
18、g 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 to form a smooth, contin
19、uouscoating 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 23 6 1C inaccordance with
20、 Method C of Test Methods D 374.8.2 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 seller).8.3 Fill the bed with fre
21、sh, 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 rapidly insert them in the aera
22、ted 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. Submersion timedepends on thickness d
23、esired, 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 and B and also the two diago
24、nals 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 thicknessavg face thickness3
25、100 (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.10. Report10.1 Report the following information:10.1.1 Powder desig
26、nation,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.FIG. 1 Aerated Bed(in.) mm (in.) mm18 3.212 12.714 6.4 4 102NOTE 1AISI 52100 steel hardened to Rockwell C55 to C60 andground
27、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 BarD296707211. Precision and Bias11.1 The precision of this test method has not been deter-mined.NOTE 3Operators fami
28、liar 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 test method has no bias because the v
29、alue 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 coatingSUMMARY OF CHANGESCommittee D01 has identified the location of selected changes to this standard since the last issue(
30、D 2967 - 02a) that may impact the use of this standard. (Approved June 1, 2007.)(1) Changed the term powder plastic coatings to powdercoatings to reflect the fact that the method can be used for allknown powder coatings.(2) Removed dip process in 8.4, as there is no known data tojustify the dip rate
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34、tee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 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).D2967073
