ASTM_C_282_-_10_2015.pdf

Designation:C28210(Reapproved 2015)Standard Test Method forAcid Resistance of Porcelain Enamels(Citric Acid Spot Test)1This standard is issued under the fixed designation C282;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.This standard has been approved for use by agencies of the U.S.Department of Defense.INTRODUCTIONThe described method furnishes a means of testing and grading glossy porcelain enamels withrespect to their resistance to citric acid at room temperature.Citric acid has been selected because itis the most common and one of the more severe of the food acids in its action on conventionalporcelain enamels.The degree of etching by a citric acid solution provides a good indication of thesusceptibility of attack of a porcelain enamel coating to common food-based acids.1.Scope1.1 This test method covers a procedure for evaluatingporcelain enamels in their resistance to citric acid exposure atroom temperature.No attempt is made to categorize porcelainenamels as to their acid-resistance or non acid-resistanceproperties,since the requirements in the several branches of theindustry differ.1.2 The test method is applicable for ware of various shapesproviding they contain a substantially flat area approximately50 mm in diameter.1.3 The test method is not applicable to finishes on chemicaland hospital ware,which may come in contact with strongmineral acids,nor to cooking utensils,which may come inprolonged contact with hot acid solutions.1.4 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.Summary of Test Method2.1 The test method consists of a 15 min exposure of the testsurface to a small pool of 10%citric acid,and an evaluation ofthe effect in terms of the change in appearance and the“relativecleanability”of the surface resulting from the treatment.3.Significance and Use3.1 This test method is intended specifically for testing theporcelain enamel finish on stoves,refrigerators,table tops,sinks and other sanitary ware,laundry appliances,architecturalunits,etc.,where the surface may come in contact with foodacids at room temperature.3.2 Citric acid has been chosen as the test medium becauseit is one of the most common of the food acids and willgenerally provide a measurable result in its action on porcelainenamel.4.Apparatus4.1 Dropper Bottle,or medicine dropper,4.2 Watch Glass,25 mm in diameter with fire polished edge,4.3 Towel,soft cotton,and4.4 Drafting Pencil,conventional graphite,degree 3B.5.Reagents and Materials5.1 Citric Acid SolutionDissolve 10 g of anhydrous citricacid crystals(H3C6H5O7)in 100 mLof water.Solution shall beprepared not more than 48 h prior to use.5.2 Cleaner SolutionDissolve 10 g of trisodium phosphate(Na3PO4)in 1 L of tap water.6.Sampling6.1 The test specimens may be articles of commerce,piecescut from articles of commerce,or laboratory specimens pre-pared especially for this test.NOTE1Processing variables in the application and drying and firingoperations materially affect the degree of attack by the acid on the surfaceof porcelain enamels.Sample specimens used for classification of acid1This test method is under the jurisdiction ofASTM Committee B08 on Metallicand Inorganic Coatings and is the direct responsibility of Subcommittee B08.12 onMaterials for Porcelain Enamel and Ceramic-Metal Systems.Current edition approved May 1,2015.Published May 2015.Originallyapproved in 1951.Last previous edition approved in 2010 as C282 10.DOI:10.1520/C0282-10R15.This test method is based on the Test for Acid Resistance of Porcelain Enamels(Citric Acid Spot Test)Bulletin T-21,of the Porcelain Enamel Institute.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 resistance must be processed under identical conditions to the commercialware they represent.7.Procedure7.1 Thoroughly wash area to be tested using a soft cottontowel moistened with a warm,1%solution of trisodiumphosphate.Rinse in warm,running tap water,and dry with asoft towel by blotting.Store the specimen at a temperature of26 6 1C(79 6 2F)for a time sufficient to bring it within thisrange prior to and during the test.NOTE2If,when rinsing,the water gathers in drops on the surface,repeat washing treatment until water spreads evenly.7.2 On articles of commerce,select areas that are horizontalor nearly horizontal in service.Place the specimen in a positionsuch that a flat area at least 38.1 mm in diameter is horizontal.With the specimen and the citric acid solution at 26 6 1C(796 2F),place several drops of the so