DIN EN ISO 9227 NSS PDF

The salt spray or salt fog test is a standardized and popular corrosion test method, used to check corrosion resistance of materials and surface coatings. Usually, the materials to be tested are metallic although stone, ceramics, and polymers may also be tested and finished with a surface coating which is intended to provide a degree of corrosion protection to the underlying metal. Salt spray testing is an accelerated corrosion test that produces a corrosive attack to coated samples in order to evaluate mostly comparatively the suitability of the coating for use as a protective finish. The appearance of corrosion products rust or other oxides is evaluated after a pre-determined period of time.

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ICS In case of doubt, the German-language original shall be considered authoritative. English price group 13 www. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by November , and conflicting national standards shall be withdrawn at the latest by November Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights.

Therefore, the test results should not be regarded as a direct guide to the corrosion resistance of the tested metallic materials in all environments where these materials might be used. Also, the performance of different materials during the test should not be taken as a direct guide to the corrosion resistance of these materials in service. Nevertheless, the method described gives a means of checking that the comparative quality of a metallic material, with or without corrosion protection, is maintained.

Salt spray tests are generally suitable as corrosion protection tests for rapid analysis for discontinuities, pores and damage in organic and inorganic coatings. In addition, for quality control purposes, comparison can be made between specimens coated with the same coating. As comparative tests, however, salt spray tests are only suitable if the coatings are sufficiently similar in nature. It is often not possible to use results gained from salt spray testing as a comparative guide to the long?

It also describes the method employed to evaluate the corrosivity of the test? It does not specify the dimensions of test specimens, the exposure period to be used for a particular product, or the interpretation of results.

Such details are provided in the appropriate product specifications. The salt spray tests are particularly useful for detecting discontinuities, such as pores and other defects in certain metallic, organic, anodic oxide and conversion coatings. It particularly applies to: — metals and their alloys, — metallic coatings anodic and cathodic , — conversion coatings, — anodic oxide coatings, and — organic coatings on metallic materials.

It has also been found suitable for testing anodic coatings on aluminum. The copper? The salt spray methods are all suitable for checking that the comparative quality of a metallic material, with or without corrosion protection, is maintained.

They are not intended to be used for comparative testing as a means of ranking different materials relative to each other with respect to corrosion resistance. For dated references, only the edition cited applies.

For undated references, the latest edition of the referenced document including any amendments applies. Check the pH using electrometric measurement or in routine checks, with a short? Make any necessary corrections by adding hydrochloric acid, sodium hydroxide or sodium bicarbonate solution of analytical grade. Possible changes in pH may result from loss of carbon dioxide from the solution when it is sprayed. If the pH of the solution initially prepared is 3,0 to 3,1, the pH of the sprayed solution is likely to be within the specified limits.

Make any necessary corrections by adding glacial acetic acid or sodium hydroxide of analytical grade. Adjust the pH using the procedures described in 3. The upper parts of the cabinet shall be designed so that drops of sprayed solution formed on its surface do not fall on the specimens being tested. The size and shape of the cabinet shall be such that the collection rate of solution in the cabinet is within the limits specified in Table 2, measured as specified in 8.

Preference shall be given to apparatus that has a means for properly dealing with fog after the test, prior to releasing it from the building for environmental conservation, and for drawing water prior to discharging it to the drainage system. The temperature shall be measured at least mm from the walls. The compressed air supplied to the atomizers shall be passed through a filter to remove all traces of oil or solid matter, and the atomizing pressure shall be at an overpressure of 70 kPa1 to kPa.

The appropriate temperature depends on the pressure used and on the type of atomizer nozzle and shall be adjusted so that the rate of collection of spray in the cabinet and the concentration of the collected spray are kept within the specified limits see 8. In Table 1, guiding values are given for the hot-water temperature in the saturation tower at different pressures. The level of the water shall be maintained automatically to ensure adequate humidification.

Baffles may be used to prevent direct impact of the spray on the test specimens, and the use of adjustable baffles is helpful in obtaining uniform distribution of the spray within the cabinet. For this purpose, a dispersion tower equipped with an atomizer may also be helpful.

The level of the salt solution in the salt reservoir shall be maintained automatically to ensure uniform spray delivery throughout the test. Suitable funnels have a diameter of mm, which corresponds to a collecting area of approximately 80 cm2. The collecting devices shall be placed in the zone of the cabinet where the test specimens are placed, one close to an inlet of spray and one remote from an inlet. They shall be placed so that only mist, and not liquid falling from specimens or from parts of the cabinet, is collected.

However, in such circumstances, the equipment shall be thoroughly cleaned and checked using the method described in Clause 5, ensuring in particular that the pH of the collected solution is correct throughout the entire spraying period. After this procedure, the specimens to be tested are placed in the cabinet.

NOTE During permanent operation, a reasonable time period between two checks of the corrosivity of the apparatus is generally considered to be 3 months. To determine the corrosivity of the tests, reference? As a complement to the reference?

Cut these reference specimens from cold? Clean the reference specimens carefully, immediately prior to testing. Besides the specifications given in 6. Carry out the cleaning in a vessel full of solvent.

After cleaning, rinse the reference specimens with fresh solvent and then dry them. Protect one face of the reference specimens with a removable coating, for example an adhesive plastic film. The edges of the reference test specimens may be protected by the adhesive tape as well. The support for the reference specimens shall be made of, or coated with, inert materials such as plastics. The lower edge of the reference specimens shall be level with the top of the salt spray collector.

The test duration shall be 48 h. The test cabinet shall be filled with dummy specimens of inert materials, such as plastic or glass, during the verification procedure. Remove the corrosion products by mechanical and chemical cleaning, as described in ISO After each stripping, thoroughly clean the reference specimens at ambient temperature with water, then with ethanol, followed by drying.

Weigh the reference specimens to the nearest 1 mg. Divide the determined mass loss by the area of the exposed surface area of the reference specimen in order to assess the metal mass loss per square metre of the reference specimen. It is recommended that freshly prepared solution be used during each procedure for the removal of corrosion products. Clean the reference specimens carefully, immediately before testing.

After cleaning, rinse the reference specimens with fresh solvent, and then dry them. The edges of the reference test specimens may be protected by the adhesive tape as well 5. The test duration shall be 24 h.

The test cabinet shall be filled with dummy specimens of inert materials such as plastic or glass during the verification procedure. Remove the corrosion products by mechanical and chemical cleaning as described in ISO After cleaning, rinse the reference specimens with fresh solvent, then dry them. The test duration is 24 h. When not specified, these parameters shall be mutually agreed between the interested parties.

Annex C describes how test panels with organic coatings are to be prepared for testing. Annex D gives supplementary information needed for testing test panels with organic coatings. The cleaning method employed shall depend on the nature of the material, its 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 careless handling. Unless otherwise specified, the cut edges shall be adequately protected by coating them with a suitable material, which remains stable under the conditions of the test, such as paint, wax or adhesive tape.

In the case of irregular surfaces, for example entire components, these limits shall be adhered to as closely as possible. The specimens may be placed at different levels within the cabinet as long as the solution does not drip from specimens or their supports at one level onto other specimens placed below.

However, for a new examination or for tests with a total duration exceeding 96 h, location permutation of specimens is permitted8. If it is necessary to suspend specimens, the material used shall not be metallic but shall be synthetic fibre, cotton thread or other inert insulating material. After it has been confirmed that the test conditions are within a specified range, stop spraying the salt solution, fill the test chamber with test specimens and start the test.

The average rate of collection of solution in each device shall be measured over a minimum period of 24 h of continuous spraying. During operation, the solution should be free from dust and should be isolated from ambient air to prevent the concentration of sodium chloride and the pH from fluctuating. When not specified, this period shall be agreed upon by the interested parties.

Recommended periods of exposure are 2 h, 6 h, 24 h, 48 h, 96 h, h, h, h, h and 1 h. 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 from outside the cabinet.

For this reason, this type of specimen should not be tested with other specimens requiring tests of predetermined durations.

Before they are examined, carefully remove the residues of spray solution from their surfaces. How to treat specimens after testing should, in line with good engineering practice, be included in the test specification. NOTE It is good engineering practice to define the appropriate criteria in the specification for a coating or a product to be tested. Report the result obtained for each specimen tested and, when appropriate, the average result for a group of replicate test specimens.

Photographic records of the tested specimens may, if required, accompany the report. This information may vary according to the purpose of the test and the guidelines prescribed, but a general list of the details likely to be required is as follows: a a reference to this International Standard; b type and purity of salt and water used; c description of the material or product tested; d dimensions and shape of the test specimen, and nature and area of the surface tested; e preparation of the test specimen, including any cleaning treatment applied and any protection given to edges or other special areas; f known characteristics of any coating, with an indication of the surface area; g number of test specimens subjected to the test representing each material or product; 14 Normen-Download-Beuth-JOPP GmbH-KdNr.

Front view Figure A. Side view Figure A. Before testing, the reference specimens shall be cleaned carefully with a hydrocarbon solvent in order to remove all evidence of dirt, oil, or other foreign matter liable to influence the result of the corrosion rate determination. After drying, the reference specimens shall be weighed to the nearest 1 mg.

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ICS In case of doubt, the German-language original shall be considered authoritative. English price group 13 www. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by November , and conflicting national standards shall be withdrawn at the latest by November Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights.

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ISO specifies the apparatus, the reagents and the procedure to be used in conducting the neutral salt spray NSS , acetic acid salt spray AASS and copper-accelerated acetic acid salt spray CASS tests for assessment of the corrosion resistance of metallic materials, with or without permanent or temporary corrosion protection. It also describes the method employed to evaluate the corrosivity of the test cabinet environment. It does not specify the dimensions or types of test specimens, the exposure period to be used for a particular product, or the interpretation of results. Such details are provided in the appropriate product specifications.

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