1、Designation:D786821Standard 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,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.5 This international standard was developed in accor-dance with international
6、ly 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.Referenced Documents2.1 ASTM Standards:2D610 Practice for
7、 Evaluating Degree of Rusting on PaintedSteel 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
8、dust or powder during a free fall 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 A structural frame is erected and enclosed unless a dryfall/fog test chamber or laboratory space
9、 is pre-designated.Spray targets are placed at the top,inside the enclosure.Foursteel panels coated with an automotive basecoat/clear coatsystem are placed on the enclosure floor to collect the dry fall.(Panels coated with other systems or uncoated panels,or both,can be used when they are deemed to
10、be more representative.)A duplicate panel set is maintained at the prevailing airtemperature,while the other duplicate panel set is heated inoven and placed inside the enclosure immediately prior toatomizing the coating.The coating is atomized against thetargets at each of two distances and the pane
11、ls are removed forevaluation.Two of the coated steel panels remain at laboratoryambient conditions,while the“pre-heated”panels are returnedto a laboratory oven.The heated and ambient coated panels arecleaned and evaluated after 24-h for dry fall attachment.5.Significance and Use5.1 Attachment of ove
12、rspray particles to vehicles and othersurfaces not intended to be coated can result in propertydamage and insurance claims.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
13、,vacuumed or washed from the surfaceswith no damage.This practice can be used to evaluate the dryfall properties of coatings 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 elevat
14、ed temperature.6.Reagents6.1 Commercially available Car Washing Concentrate.6.2 Mineral Spirits.1This practice is under the jurisdiction of ASTM Committee D01 on Paint andRelated Coatings,Materials,and Applications and is the direct responsibility ofSubcommittee D01.46 on Industrial Protective Coati
15、ngs.Current edition approved Nov.1,2021.Published November 2021.Originallyapproved in 2013.Last previous edition approved in 2017 as D7868 13(2017).DOI:10.1520D7868-21.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Boo
16、k 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 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