Is 9844 1981
Is 9844 1981
Is 9844 1981
1.SCOPE
1.1Thisstandard specifies the apparatus, the reagent and the procedure to
be used in conducting the neutral salt spray test for assessment of the quality
of coatings made in accordance with the requirements of coating or product
specifications.
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IS : 9844- 1981
1.2 It does not specify the type of test specimen, the exposure period to be
used for a particular product or the interpretation of results. Such details
are provided in the appropriate coating or product specifications.
2. TEST SOLUTION
2.1 The test solution shall be prepared by dissolving sodium chloride in
distilled or de-ionized water to produce a concentration of 50 f 5 g/l. The
sodium chloride shall be white and shall give a colourless solution in water.
It shall be substantially free from copper and nickel and shall not contain
more than 0.1 percent of sodium iodide and not more than O-4 percent of
total impurities calculated for dry salt. .If the pH of the solution as prepared
is outside the range 6.0 to 7.0, the presence of undesirable impurities in the
salt or the water or both shall be investigated.
2.2 The pH of the salt solution shall be adjusted so that the pH of sprayed
solution collected within the test cabinet ( see 3.1.4 ) will be between 6.5 and
7.2. Control of the pH shall be based on electrometric measurement at 25°C
but a short-range pH paper which can be read in increments of 0.3 pH unit
or less and ‘which has been calibrated against electrometric measurements
may be used in routine checks. Any necessary correction shall be made by
additions of solutions of hydrochloric acid or sodium hydroxide of analytical
grade.
2.2.1 Attention is drawn to the possible changes in pH resulting
from loss of carbon dioxide from the solution when it is sprayed.
Such changes may be avoided by reducing the carbon dioxide content of the
solution byj for example, heating it to a temperature above 35°C before it is
placed in the apparatus or by making the solution from freshly boiled water.
2.3 The solution shall be filtered before it is placed in the reservoir of
the ,apparatus, in order to remove any solid matter which might block
the apertures of the spraying device.
3. A&ARATUS
3.1 ‘The apparatus shall comprise the following components.
3.1.1 A Spray Cabinet, made of or lined with, material resistant to
corrosion by the sprayed solution. The cabinet shall have a volume of
not less than 0.2 ms and preferably of not less than 0.4 m* since, with
smaller volumes, difficulties are experienced in ensuring even distribution of
spray. The upper parts shall be so shaped that drops of sprayed solution
accumulated on them do not fall on specimens being tested.
The size and shape of the cabinet shall be such that the quantity
of solution collected in the cabinet is within the limits stated in 6.2.
3.1.2 Means of Supplying and Controlling Heat - Adequate to maintain
the cabinet and its contents at the specified temperature (see 6.1). The
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IS:9844-1981
4. TEST SPECIMENS
4.1 The number and type of test specimens, their shape and their dimensions
shall be seIected according to the specification covering the coating on
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IS : 9844 - 1981
product being tested. When not so specified, details concerning the speci-
mens shall be mutually agreed between the interested parties.
4.2 The specimens shall be thoroughly cleaned before testing. The cleaning
method employed shall depend on the nature of the surface and the
contaminants, and shall not include the use of any abrasives or solvents which
may attack the surface of the specimens.
Care shall be taken that specimens are not recontaminated after cleaning
by excessive or careless handling.
4.3 If test specimens are cut from a larger coated article, the cutting shall be
carried out in such a way that the coating is not damaged in the area adjacent
to the cut. Unless otherwise specified, the cut edges shall be adequately
protected by coating them with a suitable medium, stable under the condi-
tions of the test, such as paint, wax or adhesive tape.
5. METHOD OF EXPOSURE OF TEST SPECIMENS
5.1 The specimens shall be so placed in the cabinet that they are not in the
direct line of travel of spray from the atomizer. Baflles may be used to pre-
vent direct impact of the sprayed solution and the specimens.
5.2 The angle at which the sample is exposed in the cabinet is very impor-
tant. The surface shall in principle, be flat and placed in the cabinet facing
upwards at an angle as close as possible to 20’ to the vertical. This angle
shall, in all cases, be within the limits 15 to 30”.
In the case of irregular surfaces, for example, entire components, these
limits shall be adhered to as closely as possible.
5.3 The specimens shall be so arranged that they do not come into contact
with one another or with the cabinet and that surfaces to be tested are
exposed to free circulation of spray. Specimens may be placed at different
levels within the cabinet as long as the solution may not drip from speci-
mens or their supports at one level onto other specimens placed below.
5.4 The support for the specimens shall be made of inert non-metallic
material such as glass, plastics or suitably coated wood. Ifit is necessary to
suspend test specimens, the material used shall on no account be metallic and
shall be synthetic fibre, cotton thread or other inert insulating material.
6. OPERATING CONDITIONS
6.1 The temperature inside the spray cabinet shall be 35f2”C with the
minimum possible fluctuation throughout the cabinet during the test.
6.2 The solution collected in each of the collecting devices (see 3.1.4) shall
have a sodium chloride concentration of 50f 10 g/l and a pH value in the
range 6.5 to 7.2 (see 2.2).
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IS :9&4- ml
7. DURATION OF TESTS
7.1 The period of test shall be as designated by the specification covering
the coating or product being tested. When not specified, it shall be mutually
agreed between the interested parties.
Recommended periods of exposure are 2h, 6 h, 24 h, 48 h, 96 h, 240 h,
480 h and 720 h.
7.2 Spraying shall not be interrupted during the prescribed test period. The
cabinet shall be opened only for brief visual inspections of the test specimens
in position and for replenishing the salt solution in the reservoir if such
replenishment cannot be carried out froin outside the cabinet.
7.3 If the end-point of the test depends on the appearance of the first sign
of corrosion, the specimens not to be inspected frequently. For this reason
such specimens shall not be tested together with other specimens requiring
tests of predetermined duration.
7.4 A periodic visual examination of specimens under test for a
predetermined period may be made but the surfaces under test shall not be
disturbed and the period for which the cabinet is open shall be the minimum
necessary to observe and record any visible changes.
8.1 At the end of the test period, remove the specimens from the cabinet.
Allow the specimens to dry for half to one hour before rinsing, in order to
reduce the risk of removing corrosion products. Before they are examined,
carefully remove residues of the spray solution from their surfaces. A
suitable method is to rinse or dip the specimens gently in clean running
water at a temperature not exceeding 40°C and then to dry them immedia-
tely in a stream of compressed air at a pressure not exceeding 200 kPa, at a
distance of approximately 300 mm.
9. EVALUATION OF RESULTS
9.1 Many different criteria for the evaluation of the reSUlk3 Of Ihy test ‘=Y
be applied to meet particular requirements, for example, change ln means,
alteration revealed by micrographic examination or change iqmechamcal
properties. Usually the appropriate criteria will be indicated m the spccl-
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IS: 9844-1981
fixation
for the coating or product tested. For most routine applications of
the test, only the following need be considered:
a) appearance after test;
b) appearance after removing superficial corrosion products;
c) the number and distribution of corrosion defects, that is, pits, cracks,
blisters, etc, these may conveniently be assessed by methods such as
that described in IS : 6009-1970*; and
d) the time elapsing before the appearance of the first sign of corrosion.
10.TEST REPORT
10.1 The test report shall indicate the outcome of the test according to the
criteria for evaluation of results prescribed for the test. The result obtained
for each specimen tested and, when appropriate, the average result for a
group of replicate test specimens shall be reported. The report may, if
required, be accompanied by photographic records ,of the tested specimens.
10.2The report shall contain information about the test procedure. This
information may vary according to the purposes of the test and to the
directions prescribed for it but a general list of the details likely to be
required is as f0llOWS:
a) the description of the coating or product tested;
b) dimensions and shape of the test specimen and the nature and area
of the surface tested;
c) preparation of the test specimen, including any cleaning treatment
applied and any protection given to edges or other special areas;
4 known characteristics of any coating, with an indication of the
surface finish;
e) the number of test specimens subjected to the test representing each
coating or product;
f) the method used to clean test specimens after the test with, when
appropriate, an indication of the loss in mass resulting from the
cleaning operation;
s) the angle at which the tested surfaces were inclined,
h) the test temperature;
j) the duration of test;
k) the properties of any test panels placed in the cabinet expressly to
check the correctness of the operating conditions and the results
obtained with them.