GOST 9.021-74
GOST 9.021−74 unified system of protection against corrosion and ageing (ESSEX). Aluminum and aluminum alloys. The accelerated test methods for intercrystalline corrosion (with Amendments No. 1, 2)
GOST 9.021−74
Group Т99
STATE STANDARD OF THE USSR
Unified system of protection against corrosion and aging
ALUMINUM AND ALUMINUM ALLOYS
The accelerated test methods for intercrystalline corrosion
Unified system of corrosion and ageing protection.
Aluminium and aluminium alloys. Accelerated test
methods for intercrystalline corrosion
Date of introduction 1975−01−01
Promulgated by decree of the State Committee of standards of the USSR Council of Ministers dated 19 March 1974 629 N
REISSUE with amendments No. 1, 2 approved in January 1978, January 1983 (ICS 3−78, 5−83)
This standard applies to aluminium and its alloys without protective coatings and establishes methods of accelerated tests for intergranular corrosion.
1. GENERAL PROVISIONS
1.1. The comparison should be carried out with alloys, the nature and extent of corrosion damage which (in the chosen test method) are known.
1.2. Tests should be conducted in solution I, containing: 3% sodium chloride solution according to GOST 4233−77 plus 1% hydrochloric acid according to GOST 14261−77 (30 g/DMsodium chloride plus 10 cm
/DM
of hydrochloric acid density of 1.19 g/cm
), the solution temperature is 18−25 °C, test duration 24 hours
Allowed to test and in solution II containing: 1 n solution of sodium chloride plus 0.3% hydrogen peroxide according to GOST 177−88 (58 g/DMsodium chloride plus 10 cm
/DM
33% solution of hydrogen peroxide), solution temperature (30±5) °C, test duration 6 h.
(Changed edition, Rev. N 2)
.
1.3. Samples should be hung so that they do not touch and are below the level of solution above each of them during the tests was not less than 20 mm above the top edge and the same for all samples. Is possible to install the rings from the pipes directly on the bottom of the bath.
1.4. The ratio of solution volume to sample surface should be 6 cm/cm
.
(Changed edition, Rev. N 1).
2. SAMPLE REQUIREMENTS
2.1. For testing should be applied to flat samples of 20x10 mm, thickness up to 5 mm.
Allowed other forms and dimensions of samples (for example: rings cut from the pipe samples with weld, rivets, etc.).
(Changed edition, Rev. N 1).
2.2. Sampling should be conducted in such a way to include the most typical areas of the billet of the test material or part (e.g. from the edge or the center of the sheet, fine and of solid cross-section profile, etc.).
2.3. The surface of the samples must preserve the original state of the workpiece or finished part or has to be processed mechanically to a surface roughness of not more than 2.5 µm according to GOST 2789−73.
(Changed edition, Rev. N 1).
2.4. Samples of clad alloys should be tested without plating. A plating layer is removed from both sides by etching in a 5−10% solution of caustic soda according to GOST 2263−79при a temperature of 60−70 °C until complete removal of plating, washed in running cold water and clarified 2−6 min at 25−30% strength solution of nitric acid according to GOST 701−89, again washed in running cold water and then in distilled water according to GOST 6709−72, and dried with filter paper.
(Changed edition, Rev. N 2).
2.5. Cast alloys should be tested with the foundry foundry peel or without peel.
2.6. Labeling of samples according to GOST 9.909−88*. Seat marking must be protected with varnish AK-20 or other transparent varnish having the required protective properties.
_________________________
* In the index «national standards» for 2001 — GOST 9.909−86. Note the «CODE».
2.7. Tests should be conducted on at least three samples that have the same shape, size and surface preparation.
3. TESTING
3.1. Sample preparation
The samples before the test degreased by organic solvent (acetone, technical gasoline, paint remover WFD, etc.), and dried with filter paper.
3.2. Before the test, the solution I samples etched for 2−5 minutes 5−10% strength sodium hydroxide solution at a solution temperature of 45−60 °C and clarified in a 25−30% strength solution of nitric acid. Washing and drying should be performed as specified in claim 2.4.
After removal of the plating (see p.2.4) re-etching is not produced.
3.3. Before the test, in solution II the samples after degreasing and drying etched for 2 min in a solution containing: 50 cmof nitric acid (70% strength), 5 cm
fluoride-hydrogen acid according to GOST 10484−78 (48%) and 945 cm
of water, at a solution temperature of (95±3) °C; then washed in cold water, clarified in a 25−30% strength nitric acid solution, then washed again and dried with filter paper.
(Changed edition, Rev. N 2).
3.4. Before testing the samples, inspect and wash with a cotton swab moistened with ethyl alcohol according to GOST 5962−67.
3.5. Tests should be conducted in containers made of glass or inert organic materials.
3.6. The samples after testing should be rinsed in running water.
3.7. The samples after washing are dried at a temperature of (100±5) °C for at least 5 min or incubated in a desiccator over silicagel for 24 h and then made thin sections.
4. EVALUATION OF TEST RESULTS
4.1. The assessment should be performed by metallographic methods, in this case record the nature of corrosion, the maximum depth of intergranular corrosion in microns, and distribution of corrosion along the edge of the socket (isolated areas or almost the entire edge of the cone).
4.2. For this purpose it is necessary to make sections according to GOST 1778−80 on the side of the sample, previously cut by at least 5 mm in the transverse plane.
4.3. The time interval from the end of the test before the viewing cone should be no more than 7 days.
4.4. Thin section subjected to microcleaving by increasing 100−200in netravlenoy the form, inspect the entire surface of the polished end face.
4.5. If necessary, identify the microstructure of the alloy, the etching should be made in the solution of the following composition, see:
nitric acid (70% probability) to 2,5;
hydrochloric acid (concentrated) — 1,5;
hydrofluoric acid (48%) — 1,0;
distilled water and 95.0.
It is possible to use other solutions, revealing the microstructure.
(Changed edition, Rev. N 2).
