ASTM_D_3456_-_18.pdf

Designation:D345618Standard Practice forDetermining by Exterior Exposure Tests the Susceptibilityof Paint Films to Microbiological Attack1This standard is issued under the fixed designation D3456;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 provides guidelines for determining thesusceptibility of paint films to microbiological attack onexterior exposure.While it is recognized that various organ-isms may occur on an exposed coating,the specific types oforganisms are mainly of academic interest.The degree towhich microbiological discoloration occurs is the primaryconcern.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 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.1.4 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.Referenced Documents2.1 ASTM Standards:2D1006 Practice for Conducting Exterior Exposure Tests ofPaints on WoodD1849 Test Method for Package Stability of PaintD3274 Test Method for Evaluating Degree of Surface Dis-figurement of Paint Films by Fungal or Algal Growth,orSoil and Dirt AccumulationD6132 Test Method for Nondestructive Measurement of DryFilm Thickness of Applied Organic Coatings Using anUltrasonic Coating Thickness GageD7091 Practice for Nondestructive Measurement of DryFilm Thickness of Nonmagnetic Coatings Applied toFerrous Metals and Nonmagnetic,Nonconductive Coat-ings Applied to Non-Ferrous Metals3.Summary of Practice3.1 Simple observation of a coated object subjected toexterior exposure is considered a practical and reliable methodfor determining the degree that microorganisms discolor thecoating.However,this applies to a specific coated objectexposed under a given set of conditions.It should be recog-nized that there are critical factors that influence the amount offungal growth that may occur on the same coated object whenexposed to other conditions.These factors include the geo-graphic location,local atmospheric conditions such as the dustand pollen content of the air,angle of exposure,degree towhich the coating is subjected to weathering,effects ofmoisture and sunlight,the substrates on which the coating isapplied,and the coatings in the paint system under test.Thelatter factor includes the stability of the coating while packagedin the container,as well as the composition of the coatingsincluded in the total system and the thickness of each coatingapplied.Thus,while microorganisms occur on the surface ofthe last film applied,the degree of microbiological growth thatwill occur is also influenced by the composition of theundercoats.All the above factors should be considered in theselection of a coating resistant to discoloration by microorgan-isms.4.Significance and Use4.1 The growth of fungi and algae in and on the surface ofpaint films represents a major cause of discoloration ordisfigurement of painted surfaces.This practice covers thepreparation of coatings for testing,their application onsubstrates,and the arrangement of the coated panels on exteriortest fences to determine the degree of microbiological attackthat may occur on the surface of the coatings over a period oftime.This practice is intended to provide guidelines for,and adiscussion of,the various factors critical in selection of exteriorcoatings resistant to discoloration or disfigurement by algaeand fungi.1This practice is under the jurisdiction of ASTM Committee D01 on Paint andRelated Coatings,Materials,and Applications and is the direct responsibility ofSubcommittee D01.28 on Biodeterioration.Current edition approved July 1,2018.Published July 2018.Originally approvedin 1975.Last previous edition approved in 2012 as D3456 86(2012).DOI:10.1520/D3456-18.2For 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.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