1、Designation:D786813Standard Practice forDetermining the Dry Fall(Fog)Properties of ProtectiveCoatings1This standard is issued under the fixed designation D7868;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 practice covers a procedure for qualitatively evalu-ating the dry fall properties of coatings.The establishment ofthe test environm
3、ent and the evaluation procedures are de-scribed.1.2 This practice uses panels containing an automotivefinish since these types of surfaces are often the primaryconcern relating to overspray damage.Panels coated with othersystems may be used as collection surfaces when they aredeemed to be more repr
4、esentative.1.3 The values stated in inch-pound units are to be regardedas standard.The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.4 This standard does not purport to address all of thesafety concerns,if
5、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:2D610 Practice for Evaluating Degree of Rusting on P
6、aintedSteel SurfacesD5402 Practice for Assessing the Solvent Resistance ofOrganic Coatings Using Solvent Rubs3.Terminology3.1 Definitions:3.1.1 dry/fall/fog coating,nan interior or exterior coatingspecially formulated so that the fine particles of overspray dryto a dust or powder during a free fall
7、of a certain distance atspecific temperature and humidity ranges,and will not adhereto surfaces on which the overspray is subsequently deposited.4.Summary of Practice4.1 Astructural frame is erected and enclosed.Spray targetsare placed inside the enclosure.Four steel panels coated withan automotive
8、basecoat/clear coat system are placed on theenclosure floor to collect the dry fall.(Panels coated with othersystems or uncoated panels,or both,can be used when they aredeemed to be more representative.)A duplicate panel set ismaintained at the prevailing air temperature,while the otherduplicate pan
9、el set is heated in oven and placed inside theenclosure immediately prior to atomizing the coating.Thecoating is atomized against the targets at each of two distancesand the panels are removed for evaluation.Two of the coatedsteel panels remain at laboratory ambient conditions,while the“pre-heated”p
10、anels are returned to a laboratory oven.Theheated and ambient coated panels are cleaned and evaluatedafter 24-h for dry fall attachment.5.Significance and Use5.1 Attachment of overspray particles to vehicles and othersurfaces not intended to be coated can result in propertydamage and insurance claim
11、s.Dry fall coatings are formulatedsuch that overspray particles dry as they move through the air,and before they land on horizontal surfaces.These particles canthen be brushed off,vacuumed or washed from the surfaceswith no damage.This practice can be used to evaluate the dryfall properties of coati
12、ngs prior to large scale use.The practicecan also be used to evaluate whether the coating(s)possess thesame dry fall properties when the fallout collects on surfaceswith an elevated temperature.6.Reagents6.1 Commercially available Car Washing Concentrate.6.2 Mineral Spirits.7.Procedure7.1 Construct
13、a frame(enclosure)using steel conduit andcouplings or other materials of construction.The interior of theenclosure measures approximately 3 ft wide by 4 ft deep and is1This practice is under the jurisdiction of ASTM Committee D01 on Paint andRelated Coatings,Materials,and Applications and is the dir
14、ect responsibility ofSubcommittee D01.46 on Industrial Protective Coatings.Current edition approved June 1,2013.Published July 2013.DOI:10.1520D7868-13.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandar
15、ds 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 States1 19 ft high in order to permit a dry fall test distance of 18 ft.3Enclose the frame with plastic sheeting
16、 or tarpaulins andsecure,making sure there is access at the base of the enclosureto add and remove the collection surfaces(coated panels).Abase constructed of plywood and protected with paper orplastic sheeting(that can be pushed in/pulled out to load/unload the panels)may be used.This requires the frame to beheightened approximately 2 in.from the floor surface usingwooden blocks or other methods(see Fig.1).7.2 Fabricate and suspend(vertically)a spray target con-structed of18in.by 3 by 3 ft wood
