ASTM_D_2967_-_07_2013.pdf

Designation:D296707(Reapproved 2013)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.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 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 specific face thickness by dippingpreheated square bars into aerated powder and curing thecoating using predetermined conditions.NOTE1The property of corner coverage has also been referred to as“edge coverage,”though the latter is not recommended.There arewidespread misunderstandings 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 provide the electrical insulation needed insome applications.1.2The 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 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prior to use.2.Referenced Documents2.1 ASTM Standards:2D374 Test Methods for Thickness of Solid Electrical Insu-lation(Withdrawn 2013)33.Terminology3.1 Definitions:3.1.1 coating powders,nfinely divided particles of resin,either thermoplastic or thermosetting,generally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,give 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 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 flat 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 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 rate,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 plate 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.5.2 Micrometer Caliper25.4 mm(1 in.),in accordancewith Method C of Test Methods D374.5.3 Oven,with forced convection capable of maintainingthe specified temperature 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 1,2013.Published July 2013.Originally approvedin 1971.Last previous edition approved in 2007 as D2967 07.DOI:10.1520/D2967-07R13.2For 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.3The last approved version of this historical standard is referenced onwww.astm.org.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 5.4 Test Bars,four,measuring 13 by 13 by 100 mm(12by12by 4 in.)in accordance with Fig.2.5.4.1 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 te