ASTM_D_4147_-_18.pdf

Designation:D414718Standard Practice forApplying Coil Coatings Using Wire-Wound Drawdown Bars1This standard is issued under the fixed designation D4147;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.Scope1.1 This practice covers a procedure for applying a coilcoating film of uniform thickness on a flat metal panel usingwire-wound drawdown bars.1.2 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,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.3 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established 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.Summary of Practice2.1 A flat panel is secured on a firm horizontal surface.Anample amount of coating is poured across one end of the paneland the drawdown bar placed behind the coating.The bar isthen drawn with uniform pressure and speed along the lengthof the panel toward the operator to apply a uniform film.Thewet and dry film coating thickness obtained is dependent on thecombination of the bar used,the volume solids of the coating,and the speed of the drawdown motion.3.Significance and Use3.1 This practice is useful in the laboratory to simulateroll-coated films.4.Apparatus4.1 Wire-Wound Drawdown BarsA set of stainless steelwire-wound drawdown bars of sufficient diameter to preventbowing during application.These bars are manufactured sothat the diameter of the wire wound on the bar controlsthickness of the wet film applied.The choice of specificdrawdown bar is dependent on the dry film thickness requiredand the volume solids of the coating under test.Each bar isprovided a numeric identifier to help in selecting the correct barto provide a specific dry film thickness.4.2 Devices for Securing Panels:4.2.1 Magnetic Chuck for securing steel panels to eliminatebowing.4.2.2 Vacuum Plate for securing very lightweight nonmag-netic panels.4.2.3 Tape for securing the top of thin-gage panels.4.2.4 Mechanical Drives for securing panels and automat-ing the drawdown procedure.5.Hazards5.1 The flash points of most solvents used in coatings andrelated products are low enough that adequate ventilation isneeded to avoid exceeding 25%of the lower explosive limitsof the solvent when preparing and baking the panels.Thesesolvents could be toxic,care should be taken to avoid inhala-tion of the vapors and unnecessary contact of the solvents withthe skin.Consult the corresponding SDS for the specificcoating to be applied for additional hazards.6.Procedure6.1 Deburr panels so edges are smooth.Secure a flat panelto be coated on a firm,uniform,level surface.To providesufficient testing surface pour an ample amount of coatingacross the top end of the panel.Place the drawdown bar behindthe coating and pull into the coating.Rotate the drawdown barin the coating to ensure complete wetting of the coating in thethreads of the bar.Apply uniform pressure across the contactlength of the drawdown bar and hold it firmly without allowingrotation.Using only one pass,draw the bar along the length ofand off the panel at a uniform speed and pressure so that acontinuous film is produced.Application of the coating isdependent upon the rheology,type of coating,and speed andpressure to achieve the uniform desired film.Remove thecoated panel and bake,force dry,or air dry the coating inaccordance with its type so its dry film thickness can bemeasured.A heavier film thickness may be obtained along theedges of the panel and at the top of the panel where the coatingwas poured.For each additional coating layer,the side edgesmust be trimmed to eliminate the heavier areas on the previouscoat before applying an additional coat.1This practice is under the jurisdiction of ASTM Committee D01 on Paint andRelated Coatings,Materials,and Applications and is the direct responsibility ofSubcommittee D01.53 on Coil Coated Metal.Current edition approved Feb.1,2018.Published February 2018.Originallyapproved in 1982.Last previous edition approved in 2013 as D4147 99(2013).DOI:10.1520/D4147-18.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesThis 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