ASTM C282-99(2005)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: C282 – 99 (Reapproved 2005)
Standard Test Method for
Acid Resistance of Porcelain Enamels
(Citric Acid Spot Test)
This standard is issued under the fixed designation C282; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope 3.2 Citric acid has been chosen as the test medium because
it is one of the most common of the food acids and will
1.1 This test method covers a procedure for evaluating
generally provide a measurable result in its action on porcelain
porcelain enamels in their resistance to citric acid exposure at
enamel.
room temperature. No attempt is made to categorize porcelain
enamels as to their acid-resistance or non acid-resistance
4. Apparatus
properties,sincetherequirementsintheseveralbranchesofthe
4.1 Dropper Bottle, or medicine dropper,
industry differ.
4.2 WatchGlass,25mmindiameterwithfirepolishededge,
1.2 The test method is applicable for ware of various shapes
4.3 Towel, soft cotton, and
providing they contain a substantially flat area approximately
4.4 Drafting Pencil, conventional graphite, degree 3B.
50 mm in diameter.
1.3 Thetestmethodisnotapplicabletofinishesonchemical
5. Reagents and Materials
and hospital ware, which may come in contact with strong
5.1 Citric Acid Solution—Dissolve 10 g of anhydrous citric
mineral acids, nor to cooking utensils, which may come in
acid crystals (H C H O ) in 100 mLof water. Solution shall be
3 6 5 7
prolonged contact with hot acid solutions.
prepared not more than 48 h prior to use.
1.4 This standard does not purport to address all of the
5.2 Cleaner Solution—Dissolve 10 g of trisodium phos-
safety concerns, if any, associated with its use. It is the
phate (Na PO ) in 1 L of tap water.
3 4
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
6. Sampling
bility of regulatory limitations prior to use.
6.1 The test specimens may be articles of commerce, pieces
cut from articles of commerce, or laboratory specimens pre-
2. Summary of Test Method
pared especially for this test.
2.1 Thetestmethodconsistsofa15minexposureofthetest
surface to a small pool of 10 % citric acid, and an evaluation of
NOTE 1—Processing variables in the application and drying and firing
theeffectintermsofthechangeinappearanceandthe“relative operations materially affect the degree of attack by the acid on the surface
of porcelain enamels. Sample specimens used for classification of acid
cleanability” of the surface resulting from the treatment.
resistance must be processed under identical conditions to the commercial
ware they represent.
3. Significance and Use
3.1 This test method is intended specifically for testing the
7. Procedure
porcelain enamel finish on stoves, refrigerators, table tops,
7.1 Thoroughly wash area to be tested using a soft cotton
sinks and other sanitary ware, laundry appliances, architectural
towel moistened with a warm, 1 % solution of trisodium
units, etc., where the surface may come in contact with food
phosphate. Rinse in warm, running tap water, and dry with a
acids at room temperature.
soft towel by blotting. Store the specimen at a temperature of
26 6 1°C (79 6 2°F) for a time sufficient to bring it within this
range prior to and during the test.
This test method is under the jurisdiction ofASTM Committee B08 on Metallic
and Inorganic Coatings and is the direct responsibility of Subcommittee B08.12 on
NOTE 2—If, when rinsing, the water gathers in drops on the surface,
Materials for Porcelain Enamel and Ceramic-Metal Systems.
repeat washing treatment until water spreads evenly.
Current edition approved Sept. 15, 2005. Published September 2005. Originally
approved in 1951. Last previous edition approved in 1999 as C282 – 99. DOI:
7.2 On articles of commerce, select areas that are horizontal
10.1520/C0282-99R05.
ornearlyhorizontalinservice.Placethespecimeninaposition
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. such that a flat area at least 38.1 mm in diameter is horizontal.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
C282 – 99 (2005)
TABLE 1 Requirements for Respective Classes of Acid
With the specimen and the citric acid solution at 26 6 1°C (79
Resistance
6 2°F), place several drops of the solution on the test area to
Classification Requirements
form a pool, and immediately cover with a clean watch glass in
Class AA No visible stain, and
the inverted position. Use a quantity of solution that is just
Pass dry-rubbing test
sufficient to fill the inverted watch glass except for a small air
Class A Pass blurring-highlight test, and
bubble (three to six drops are usually required, depending upon
Pass wet-rubbing test
the dropper and the curvature of the watch glass).After 15 min Class B Pass blurring-highlight test, and
Fail wet-rubbing test
of treatment, remove the watch glass and immediately rinse the
Class C Fail blurring-highlight test, and
spot of solution from the surface. Dry the specimen with a dry,
Pass disappearing-highlight test
Class D Fail disappearing-highlight test
clean, soft cotton towel by blotting (not rubbing).
NOTE 3—The test surface must be thoroughly dry before grading. The
presence of a slight film of water on the surface may change the rating of
specimens near the borderline between classes.
increasing pressure, rub repeatedly across the lines with a dry,
clean, soft cotton towel as illustrated in Fig. 2. If marks are
8. Grading
completely removed from the treated a
...