Historical Version s - view previous versions of standard. More D This practice is therefore useful for evaluating coatings alone or complete coating systems. Some tests are used for a pass or fail determination at an arbitrary time.
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Designation: D? A number in parentheses indicates the year of last reapproval. A superscript epsilon? This standard has been approved for use by agencies of the U. Department of Defense. As the warmer saturated air passes the cooler specimens, water is deposited onto the specimens in the form of condensation. This makes this practice suitable for? This practice differs from other methods where condensation is only formed on the front coating surface, while the back surface is outside the exposure area.
Other tests may also deposit water droplets on the surface but where the source is not from condensation for example, water spray. Referenced Documents 2. Summary of Practice 3. It does not specify specimen preparation, or evaluation of results. The values given in parentheses are for information only. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
Current edition approved Dec. Published December Originally approved in Last previous edition approved in as D — DOI: Water permeates the coating at rates that are dependent upon the characteristics of the coating.
Any effects such as color change, blistering, loss of adhesion, softening, or embrittlement are observed and reported. This practice is therefore useful for evaluating coatings alone or complete coating systems. Some tests are used for a pass or fail determination at an arbitrary time. A coating system is considered to pass if there is no evidence of water-related failure after a period of time.
Other tests are used to monitor degree of failure as a function of exposure time. Users of this practice alone may use the known performance of the controls to set test end points. Another option is to continue the test until all specimens have failed, and use the time to reach failure as a way to differentiate performance. Corrosion tests can be conducted, as the condensate dripping off the test articles in not recirculated.
Apparatus 5. Test Specimens 6. The substrate composition and surface preparation, specimen preparation, and the number of specimens should be agreed upon prior to testing. Practices D cover application techniques for the production of uniform? Such control specimens can provide warning of changes in test severity in a given apparatus, and can indicate variations in test severity between different apparatuses.
Best practice is to use two different control specimens, one with known relatively poor performance, and one with known relatively good performance. The use of control specimens with known performance can also be used to determine the duration of the test that is required to produce meaningful results.
If more than one replicate specimen is exposed, place the replicates in different locations in the exposure area. Procedure 7. This is a requirement in order for this procedure to work correctly.
NOTE 3—Due to heat loss to the specimens and the walls of the chamber where a heated water tank is used, the temperature of the water in the tank will be above the temperature of the air and water vapor mixture.
Slotted nonmetallic supports are suitable for? Position 3-dimensional specimens on a support so that the primary surface is as close to end-use position as possible.
Material used for supports shall be of sufficient stiffness so that they do not distort or sag during prolonged use. The minimum distance between adjacent specimens or between specimens and the walls of the chamber shall be at least 30 mm.
Arrange specimens so that condensate from one specimen cannot drip on other specimens. Before using the exposure device to this standard for the? Reverify the chamber if there are any changes to the setup of the equipment or if any of the components listed in Section 5 are repaired or replaced.
Operate the test continuously with the test chamber closed unless otherwise speci? Short interruptions to inspect or remove specimens are permitted, but such interruptions should occur no more than once each day.
Rate specimens for changes in color, blistering, etc. Evaluate specimens no less than 5 min and no more than 10 min after removal from test, as the effects from water exposure can change within a short time.
Remove only as many specimens as can be rated within the speci? A recovery period from 12 to 24 h is generally sufficient. The post-recovery rating allows evaluation of the permanent effects of the exposure as distinct from the transient effects, and is especially important for evaluation of color and gloss.
Report 8. Keywords 9. After the specimens have been in an unopened chamber for at least 12 h, open the chamber and check for the presence of uniform condensation on each specimen. Specimens used for chamber veri? The minimum distance between specimens used for chamber veri? The minimum distance between adjacent test specimens shall be mm.
If any specimen does not have condensation, or the condensation is present on only part of the specimen surface, the area within mm 4 in. This saturates the air in the lower portion of the test chamber with water vapor. The saturated mixture of water vapor and air temperature rises and then cools below the dew point, causing condensation on the specimens.
Three types of apparatus have been found to meet the requirements of this practice. One type uses a water tank with an electric immersion heater, another uses a water vapor generator, and the third type uses a submerged air distribution pipe. The use of a large heated water tank would tend to make the temperature within the chamber uniform, and thus inhibit or prevent the formation of condensate on the specimens.
The level of water in the heating jacket should be approximately 30 cm 12 in. Specimens must be placed at a level above the water in the heating jacket to insure proper condensation. Air pressure to the humidifying tower should be approximately 7 to 14 kPa 1 to 2 psi.
It is difficult to produce condensation with small chambers because the temperature differential is too slight.
Circulating fans should be used with caution as their use may reduce the temperature differential and limit condensation. If condensation is not observed on any specimen immediately after the chamber is opened, discontinue the test and determine the cause of the lack of condensation before continuing. Report any instances of condensation non-uniformity if they occur during the exposure. It may be necessary to avoid placing specimens in the lower portion of the chamber as the temperature differentials at the lower levels may be too small to induce condensation.
Four typical designs are shown in Fig. Primary limit control for immersion heater 5 8—Water line 9—Insulation if necessary see X1. Primary limit control for immersion heater 6 5—Heated water tank for supplying heat and humidity to room 6—Immersion heater 7—Water temperature limit control 8—Constant level water tank unheated with over? Polyvinyl chloride pipe and? Approved December 1, Users of this standard are expressly advised that determination of the validity of any such patent rights, and the risk of infringement of such rights, are entirely their own responsibility.
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Water Resistance and Humidity (ASTM D 870, ASTM D 2247)