GOST 6032-89

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  ГОСТ 6032-89

GOST 6032−89 (ISO 3651/1−76, ISO 3651/2−76) Steel and alloys corrosion-resistant. Methods of test for resistance to intergranular corrosion

GOST 6032−89
(ISO 3651/1−76,
ISO 3651/2−76)

Group B09

STATE STANDARD OF THE USSR

STEELS AND ALLOYS CORROSION-RESISTANT

Methods of test for resistance to intergranular corrosion

Corrosion-resistant steels and alloys.
Methods for determination of intercrystalline corrosion resistance

AXTU 0909

Valid from 01.07.1990
before 01.07.1995*
___________________________
* Expiration removed by Protocol No. 4−93
The interstate Council for standardization, Metrology
and certification. (IUS N 4, 1993).
Note the «CODE».

INFORMATION DATA

1. DESIGNED AND MADE Mintyazhmash USSR

DEVELOPERS

I. G. Volikova (theme leader), Cand. tech. Sciences; V. V. Gryaznov, Y. B. Yakimovich; P. A. Kharin, PhD. tech. Sciences; Sidorkina Y. S., Cand. tech. Sciences; B. V. Lebedev, N. Abugida, PhD. tech. Sciences

2. APPROVED AND put INTO EFFECT by Decision of the USSR State Committee on management of quality and standards from 17.11.89 N 3397

3. THE TERM OF THE FIRST CHECK — 01.07.95

4. THE STANDARD FULLY COMPLIES WITH ISO 3651/1−76, ISO 3651/2−76

5. REPLACE GOST 6032−84

6. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS:

7. REISSUE


This standard specifies test methods resistance to intergranular corrosion of steel products of corrosion resisting steels and alloys, including double-layer, welded joints, weld metal and weld metal.

The standard applies to steels of the ferritic class stamps 08KH17T, 15KH25T; austenitic-martensitic class stamps 20KH13N4G9, 09H15N8YU, 07KH16N6, 09KH17N7JU, 09KH17N7JU1, 08KH17N5M3; austenitic-ferritic class stamps 08KH22N6T, 08KH21N6M2T, 08KH18G8N2T; austenitic grades 10Х14Г14Н3, 10KH14G14N4T, 10KH14AG15, 03KH16N15M3, 03KH16N15M3B, 09KH16N15M3B, 12H17G9AN4, 03KH17N14M3, 08KH17N13M2T, 10X17H13M2T, 10H17N13M3T, 08KH17N15M3T, 12H18N9, 12KH18N9T, 04KH18N10, 08H18N10, 08CR18NI10TI, 12CR18NI10TI 12H18N10E, 03Х18Н11, 06KH18N11, 03Х18Н12, 08KH18N12T, 12Х18Н12Т, 08KH18N12B, 07KH21G7AN5, 03KH21N21M4GB, iron-Nickel alloys based brands 06XH28MDT, 0ЗХН28МДТ chemical composition meet the requirements of GOST 5632. This standard could be extended to corrosion-resistant steel and alloys other brands of the same classes.

Depending on the chemical composition (grade) of steel or alloy and their purpose choose one of the methods for the determination of resistance to intergranular corrosion AM, AMA, EMUF, WU, Doo.

Allowed to test one of the additional methods, TMC, B, are given in appendices 1−3. The method of testing by these methods is mandatory.

In the legend of methods the letters stand for:

A, B, C, D — letter-name methods;

M — tested in the presence of metallic copper in the solution;

F — test in the presence of fluoride ion in the solution;

— Conducting accelerated tests.

Do conduct sophisticated tests;

TSK — tested by etching in oxalic acid.

1. SAMPLES

1.1. Blanks for samples cut out:

from a sheet thickness of not more than 10 mm, ribbons and wires — from anywhere;

from a sheet thickness more than 10 mm from the surface layers;

of long products and structural shapes round, square and hex — out of the axial zone in the longitudinal direction, of the other species — from anywhere;

from a tube blank from an axial zone in the longitudinal or transverse direction;

from pipes — from anywhere;

from forgings from overlaps or body forging;

castings — from tides or separately cast samples.

1.2. Samples of blanks made of the following types:

of sheet, tape, wire, long products and structural shapes, billets, forgings, castings, weld metal, weld metal — flat (see table.1); it is possible to produce cylindrical samples of cylindrical workpieces with a diameter not exceeding 10 mm and for the test according to the method of DU — of all the above types of steel products;

from pipes — flat, segments, rings (), ports () (see table.1), where a  — outer diameter, mm;  — height, mm;

allowed:

rings and Spigots of pipes with nominal wall thickness up to 1.5 mm subjected to flattening, smoothing, flattening and subsequent cropping of the sides to obtain a flat sample;

in pipes with a nominal external diameter not exceeding 5 mm remove ½ of the circumference wall of the tube with one of its ends or in the middle of ½ of the length of the pipe (see table.1) when testing all methods, except do;

dual-rolled and bimetallic tubes are the same as sheet metal and pipes, respectively; samples are made from a plating layer after removal machining of the main and transition layers, a test method do further removed, and cladding layer to a depth of not less than 0.5 mm from the side adjacent to the main layer; the completeness of the removal of the base layer is determined, maintaining the sample for 3−5 min at room temperature in the solution given in claim 2.2.1.

Table 1

Note. From the weld metal and weld metal produce samples similar to the flat nestarnou sample.


1.3. Size of samples for testing methods of AM, AMA, EMUF, WU should provide the ability to:

bending angle (90±3)° flat sample, segment, cylinder diameter not exceeding 8 mm and nozzle diameter of not more than 5 mm;

flattening and distribution on the cone ring, cable diameter more than 5 mm;

inspection of the surface of the bending on the lot, the width of which can reliably detect intergranular cracks.

The dimensions of the samples for the test method DM should meet the following requirements:

the largest sample size should be in the direction of rolling;

the length of the flat specimen and of a segment or the height of the cylinder and nozzle should be not less than double width or diameter, respectively;

the thickness of the flat sample must be less than its width;

the ratio of the smaller side surfaces for flat sample segment and square ends for cylinder and nozzle to the total area of the sample surface should be no more than 15%.

The calculation formula of the ratio of specimen size to the method of DU meeting the requirements given in Annex 4.

1.4. Manufacturer of billet samples of the desired thickness is carried out machining of the workpiece:

from the leaf — surfaces, in the presence of the treated surface of the metal is removed from the surface;

of long products and structural shapes, forgings, castings, billets with any of the surfaces;

from the pipes of heat — and cold — exposed surface;

of pipes hot-rolled with one or both surfaces.

In the presence of conditions of pipe metal removed from the side not in contact with the working environment.

Allowed for the sheet of austenitic steels with thickness more than 10 mm when tested by the methods of AM, AMA, EMUF, WU cut samples across the section.

1.5. Welded butt joints produce samples of various types (see table.1):

of welded joints of sheet, long products and structural shapes, castings, forgings — flat type 1 or type 2;

from electric-welded pipes — rings, tubes and segments type 2;

of circular welded pipe joints, segments, rings or tubes type 1;

of welded joints of two-layer steel after removal of the main and transition metal layers are made of the same samples as welded joints of sheet and pipes.

Methods AM and AMU, AMWF, WU, experience IN welded samples of type 1 or 2, the method do in type 2.

1.6. In the welded samples (see table.1 types 1, 2) the weld reinforcement is removed mechanically, it is allowed to process the entire surface to a depth of not more than 1 mm.

Bringing the welded joint or weld of the specimen to the desired thickness is mechanical removal of metal from the surface that is not subject to corrosive environment, in the absence of such data on the part of the surface on which the weld metal undergoes the least welding heat.

Reduction of wall thickness of welded samples from the pipes is carried out according to claim 1.4.

1.7. Covered electrodes, welding wire and welding feed control, testing weld metal or weld metal made specified filler materials.

The weld metal test on flat samples (see table.1) cut from the top layers of multilayer weld is made according to GOST 6996 controlled welding consumables (lower unused layers is allowed to perform other welding materials of similar chemical composition). When using the plate for welding, similar in chemical composition to the weld metal, the number of unused lower layers can be reduced to three.

The weld metal test on flat specimens, entirely cut only from the top layers of a multilayer controlled seam welded joints. The width of the weld metal at the point of selection of the sample should be at least 15 mm. Plates for welded joints shall be of corrosion-resistant steel of the same class and similar chemical composition as the weld metal. You may use a plate made of corrosion-resistant steel in other classes or grades, subject to prior three-layer deposition rate controlled (or similar chemical composition) of filler materials to be welded edges of the plates.

When using thin plates to provide the required width of the weld is allowed to use linings of the same steel as the plate (in the case of preliminary overlaying of edges, the same surfacing is performed on the surface of the lining).

Allowed the weld metal to test on a flat welded samples (see table.1 type 1 or 2) produced from the control welded joints resistant against intercrystalline corrosion of steel, welding of which is made of filler materials for welding this steel.

1.8. Recommended sizes for all specified samples for testing by the methods of AM, AMA, EMUF, WU, DU, is given in Appendix 5. Allowed other sample sizes.

1.9. For test methods, AM, AMA, EMUF, WU, sheets, pipes, varieties, wire, ribbon manufactures:

of austenitic steels and alloys — one set of samples (at least two pieces);

of ferritic, austenitic-martensitic, austenitic-ferritic steels — two sets of samples (four pieces), one of which is control;

each controlled forgings, castings, welded joints, weld metal, weld metal all these classes of steels and alloys of at least four samples, two of which control.

Test samples bent at an angle (90±3)° and not subjected to boiling in the solution (if necessary, control of both surfaces of the sample curve Z-shape).

To test the method do produce for all grades of steels of all of these types of steel, including welded joints, weld metal and weld metal — one set of samples (but not less than two pieces).

1.10. Unstabilized steel (not containing titanium or niobium) with a maximum permissible mass fraction of carbon not less than 0,030%, used as supplied, are the samples in the delivery condition, if there is no further guidance in the normative-technical documentation for metal products.

Stable steels and alloys (containing titanium and niobium) and unstabilized steels and alloys with a maximum permissible mass fraction of carbon not more than 0,030%, used as supplied, are the samples made of blanks of metal, subjected to further provoke the heating modes shown in table.2.

In the case of steel after heat treatment, different from the delivery condition, tests carried out on samples made of blanks subjected to the same heat treatment and provoke additional heating modes, are given in table.2 (weld provoking heat do not expose).

Table 2

The samples made from casting wild steels or alloys, subjected to the same heat treatment as the product of these castings, and the samples from the castings of stabilized steels or alloys, yet also provoking heated.

Allowed on agreement between the consumer and the manufacturer to conduct provoking heating of the other modes.

Provoking heated billet is subjected to samples.

Allowed to subject provoking heated samples.

The differences in the evaluation of the test results are provoking heated billet is subjected to samples.

Pre-fat of the workpiece loaded into the furnace, heated to a temperature of provoking heat.

1.11. Steel used in the cold-worked or polonikeman condition, tested on samples without provoking heat.

1.12. Allowed at the enterprises-manufacturers of welded products instead of testing samples with precipitating heat testing steels and alloys for welded samples, controlling the heat affected zone.

1.13. Steel and alloys, subjected to repeated heat treatment, different from the provoking of heating, after heat treatment experience on p.1.10 as a new batch of metal.

1.14. When control of welded joints, which are in the process of manufacture of the equipment to be subjected to heat treatment that alters the properties of the metal, tests carried out on welded samples subjected to the same heat treatment.

1.15. When tested by the methods of AM, AMA, EMUF, WU, oxide formed on the surface of the samples after quenching or provoking heat, before grinding, or polishing must be removed by chemical or electrochemical etching, (when tested by the method do only chemical etching) or by mechanical means. This allowed treatment of the entire surface to a depth of not more than 1 mm.

Chemical etching of samples from steels austenitic, austenitic-ferritic, austenitic-martensitic steels and iron-Nickel alloys the basis is carried out in solution composition:

the volume of nitric acid of density 1.35 g/cmaccording to GOST 4461 — (620±3) cm;

weight of ammonium fluoride according to GOST 4518 — (76,0±0,1) g;

the volume of water — (300±3) cm;

temperature (20±5) °C;

ferritic steel — structure solution:

the volume of hydrochloric acid density of 1.19 g/cmaccording to GOST 3118 — (50±1) cm;

the volume of nitric acid of density 1.35 g/cmaccording to GOST 4461 (5,0±0,1) cm;

the volume of water (50±1) cm;

the solution temperature at 50−60 °C

or electrolytically in a solution of composition:

the amount of orthophosphoric acid with a density of 1.68 g/cmaccording to GOST 6552 — (34±1) cm;

the volume of nitric acid of density 1.35 g/cmaccording to GOST 4461 (11±1) cm;

the volume of water — (955±3) cm;

density current — (0,5−0,6)·10A/m;

temperature is 40−50 °C.

The samples are etched until complete removal of scale. After etching the samples are thoroughly washed with water.

Allowed to carry out chemical etching of the other solutions in other modes, ensuring full scale removal and steel, which is resistant against intergranular corrosion, and also the absence of a preferential etching of grain boundaries and pitting.

The differences in the test results, the etching is carried out only as specified in this paragraph.

1.16. The parameter of surface roughness of samples Ra before test shall be not more than 0.8 µm according to GOST 2789. To the specified roughness is adjusted controlled surface samples, test methods, AM, AMA, EMUF, WU, and the whole surface of the samples, the test method do. The desired roughness is achieved by polishing or grinding. Overheating of the surface is not valid.

Allowed samples of cold and warm pipes, cold rolled and cold drawn metal products, and metal products with special surface finish is not subjected to polishing or grinding, if not otherwise stated in the standards community.

1.17. Before the test samples are labeled. Room knocked out or applied with electrocorundum (for brittle materials) on one or two ends of the sample at a distance of 5 to 10 mm from the end.

1.18. Before testing, the samples are degreased with organic solvents: carbon tetrachloride, acetone, gasoline, etc. quality h. d. a. Allowed not to perform degreasing of the samples loaded into the vessel immediately after etching and rinsing.

2. METHOD AM

2.1. The essence of the method

The steel samples incubated in a boiling aqueous solution of copper sulphate and sulphuric acid in the presence of metallic copper.

The method is applied to control steel grades: 20KH13N4G9, 08KH22N6T, 08KH21N6M2T, 08KH18G8N2T, 03KH16N15M3, 03KH16N15M3B, 03KH17N14M3, 08KH17N13M2T, 09KH16N15M3B, 10X17H13M2T, 10H17N13M3T, 08KH17N15M3T, 12H18N9, 12KH18N9T, 04KH18N10, 08H18N10, 08CR18NI10TI, 12CR18NI10TI 12H18N10E, 06KH18N11, 03Х18Н11, 03Х18Н12, 08KH18N12T, 12Х18Н12Т, 08KH18N12B, 08KH17T, 15KH25T, 09H15N8YU, 07KH16N6, 09KH17N7JU, 09KH17N7JU1, 08KH17N5M3, 12H17G9AN4, 07KH21G7AN5.

This is the recommended method of control for steel grades: 10Х14Г14Н3, 10KH14G14N4T, 10KH14AG15.

2.2. Reagents and solutions

Copper sulfate () according to GOST 4165 or copper sulphate according to GOST 19347.

Sulfuric acid according to GOST 4204 density of 1.83 g/cm, h. d. a. or H. h

Hydrochloric acid according to GOST 3118 density of 1.19 g/cm, h. d. a. or H. h

Nitric acid according to GOST 4461 density of 1.40 g/cm, h. d. a. or H. h. a solution with a mass fraction of 20−30%.

Distilled water (pH, chloride content, nitrate, and residue after evaporation according to GOST 6709).

Copper in the form of chips or plates according to GOST 859.

2.2.1. The solution for the test: water volume (1000±3) cmadd sulfuric acid copper weight (130,0±0,1) g, and then in small portions was added sulphuric acid volume (120±3) cm.

2.2.2. The solution for re-testing: in the water volume (1000±3) cmadd sulfuric acid copper weighing 110−160 g, and then in small portions was added sulfuric acid with a volume of (100±3) cm.

2.2.3. The solution is to identify the boundaries of the welded joints in the water of (20±1) cmdissolved sulfuric-acid copper with a mass of (4,0±0,1) g, and add hydrochloric acid with a volume of (20±1) cm.

2.3. Testing and evaluation of results

2.3.1. The test is carried out in a glass flask with a reflux condenser or in a tank of corrosion-resistant stabilised chromium-Nickel steel with lid, equipped with a reflux condenser. At the bottom of the reaction vessel is poured a layer of copper shavings, over which the loaded samples.

Allowed:

instead of copper shavings to use copper finned plate (with through holes with a diameter of 5−7 mm) on the suspension, provided that they are reliable (top and bottom) contact with the samples, good samples of the wash solution and removal of corrosion products. The differences in the evaluation of metal quality tests carried out in the presence of copper chips;

download the samples in several rows, with full contact with copper turnings or other bilateral contact with the copper plates;

joint download the following steels:

1) 08KH17T, 15KH25T;

2) 09H15N8YU, 07KH16N6, 09KH17N7JU1, 08KH17N5M3, 09KH17N7JU;

3) 08KH22N6T, 08KH18G8N2T, 08KH21N6M2T;

4) 10Х14Г14Н3, 10KH14G14N4T, 10KH14AG15, 12H17G9AN4, 07KH21G7AN5;

5) 12H18N9, 12KH18N9T, 04KH18N10, 08H18N10, 08CR18NI10TI, 12X18H10T;

6) 12H18N10E, 06Х8Н11, 08KH18N12T, 12Х18Н12Т, 08KH18N12B;

7) 09KH16N15M3B, 08KH17N13M2T, 10X17H13M2T, 10H17N13M3T, 08KH17N15M3T.

The reaction vessel is filled with a solution for the test of at least 20 mm above the sample surface or layer of the chip (copper plates) and continuously boiled. It is impossible to prevent heating of the refrigerator.

2.3.2. The duration of exposure to boiling the solution should be (of 24.00±0,25) g. If the forced break test samples of the mortar is removed. The test duration is calculated as the total number of hours of testing when boiling.

For steel grades 20KH13N4G9, 10Х14Г14Н3, 10KH14G14N4T, 10KH14AG15, 09H15N8YU, 07KH16N6, 09KH17N7JU, 09KH17N7JU1, 07KH21G7AN5, 12H17G9AN4, 08KH18G8N2T duration of exposure in the solution should be (15,00±0,25) h.

2.3.3. The differences in the evaluation of test results is carried out in a glass flask continuously. The volume of the solution should be at least 10 cmby 1 cmsample surface.

2.3.4. After soaking in the solution the samples were washed with water and dried. When the deposition on the samples of copper layer does not wash off with water, it is removed by washing the samples in 20−30% strength solution of nitric acid.

2.3.5. You can reuse the solution for the test while maintaining its color, except for the tests for differences.

2.3.6. Copper shavings or copper plates can be used repeatedly. In the case of darkening during storage, they are washed in nitric acid solution and then with water.

2.3.7. For the detection of intergranular attack after exposure in the solution samples of the curve on the angle (90±3)° according to GOST 14019 (pipe — NTD).

The radius of curvature of the mandrel depending on the grade of steel and type of steel from which is made the samples are given in table.3.

Table 3

2.3.8. If you do not know what the surface is working, then check both the sample surface. For this sample, give a Z-shaped bend. By testing samples of cladding layer of two-layer steel and bimetallic tubes bending is carried out so that the sample side, which has been removed, the base layer would be facing the inside.

2.3.9. From the seamless pipe samples-segments and flat specimens cut from straight or tapered tubes or rings, bent Z-shaped.

If the sample is difficult to give a Z-shape, the test is carried out on duplicate samples, of which one-half of the curve on the convex surface and the other on the concave.

The outer surface of the pipes, is cut of seamless tubes with outer diameter not more than 5 mm, control bend. The inner surface of metallographic control technique or when removing part of the wall of the nozzle according to claim 1.2 — bending.

Rings and pipes, made of seamless pipes with diameter more than 8 mm, control flattening according to GOST 9940 and GOST 9941 by approximating the compressive planes to distance () in mm, calculated by the formula

(1)

where  — outside diameter of pipe, mm;

 — wall thickness, mm.

When flattening samples of an austenitic-ferritic or ferritic steels distance () is calculated by the formula

(2)

The internal surface of rings and tubes is controlled by metallographic methods. Allowed for austenitic steels, the control of the inner surface of rings carry flare to a diameter determined by the formula

(3)

where the inside diameter of rings, mm.

2.3.10. Welded samples after the tests in the solution curve according to claim 2.3.7:

type 1 (see table.1) weld control weld metal; heat affected zone under the control of steels and alloys; one of the specimens of the weld seam, the second — the heat affected zone in the control welded joints and in General;

type 2 (see table.1) perpendicular to the weld seam under the control of the weld metal, heat affected zone and the welded joint as a whole; in the case of the need to control both sides of the sample curve Z-shape.

2.3.11. Allowed to identify the boundaries of weld after boiling a slight etching of the samples from 0.5 to 1 min in the solution given in claim 2.2.3.

2.3.12. The bending is carried out so that the weld is facing to the working environment, was on the outside of the sample. If the unknown side-seam facing to the working environment, on the outside of the sample should be a seam exposed to the maximum number of heatings.

2.3.13. When machining the surface of the sample (p.1.4) bending is carried out from the side, not exposed to processing.

2.3.14. Samples in the form of rings and tubes with longitudinal or circumferential seam taper according to claim 2.3.9, in accordance with GOST 6996 ring seal should be placed on the axis of compressive load, and longitudinal — Diametric plane, perpendicular to the action of compressive loads.

2.3.15. Inspection of curved samples is carried out with the help of a magnifying glass with magnification of 8−12.

2.3.16. Absence of cracks on the specimen bent after testing in solution, with the exception of the longitudinal cracks and cracks directly on the edges indicates the resistance against intergranular corrosion.

If the samples have not stood the test solution n.2.2.1, is allowed to carry out repeated tests in solution p. 2 2.2.

2.3.17. In those cases, if the Flexural test specimens break or after bending them cracks are detected, with the exception of the longitudinal cracks and cracks directly on the edges, and if the samples with thickness less than 0.1 mm bending is not detected intergranular corrosion, or if the impossible bending of the sample (due to its size), the resistance against intergranular corrosion of the samples tested in solution, estimated by metallographic methods.

Allowed to use physical control methods (see Annex 6).

2.3.18. To detect intergranular corrosion metallographic method of nesehnuti section of the sample passed corrosion test, cut a plate for the manufacture of the cone so that the plane of the cut was perpendicular to the monitored surface of the sample;

when cutting plates for socket welded sample, the cutting line should be at right angles to the weld seam and the cutting plane must include the weld metal and heat-affected zone.

Recommended length of the cone for controlled surface should be 15−20 mm.

The cutting plane should be the plane of the thin section.

A method of manufacturing a cone to ensure that no dam edges and burrs.

2.3.19. The presence and depth of intergranular corrosion set in stained sections, at magnification of at least 200. The etching is performed only to identify the weak grain boundaries.

Modes of etched thin sections and reagents for the detection of intergranular corrosion is given in Annex 7.

Thin section scan from the controlled surface.

Determine the maximum depth of fracture identified in six fields of view. In these fields of view must be included sites with the greatest depth of intergranular corrosion.

2.3.20. A symptom of resistance to intergranular corrosion metallographic control is the destruction of the grain boundaries to a maximum depth of not more than 30 µm, unless otherwise indicated in standards for steel; in the samples of steel of a thickness of less than 1.5 mm to a depth of not more than 10 µm.

3. METHOD OF AMU

3.1. The essence of the method

The steel samples incubated in a boiling aqueous solution of copper sulphate and sulphuric acid of high concentration in comparison with the method of AM in the presence of metallic copper.

The method is rapid and is used to control the same steel grades that method and AM, with the exception of the steels listed in clause 2.3.2, for which the duration of the test according to the method of AM is 15 hours

3.2. Reagents and solutions

The reagent according to claim 2.2.

The solution for testing: the water volume (1000±3) cmdissolved sulfuric-acid copper weight (50,0±0,1) g, and then in small portions was added sulfuric acid with a volume of (250±3) cm.

3.3. Testing and evaluation of results

3.3.1. The test is carried out in accordance with the requirements of paragraphs.2.3.1, 2.3.3−2.3.6.

3.3.2. The duration of exposure in the solution is (8,00±0,25) h.

3.3.3. Detection of intergranular corrosion is carried out according to claim.2.3.7−2.3.15; 2.3.17−2.3.19; evaluation of results of tests carried out on PP.2.3.16, 2.3.20.

4. METHOD AMWF

4.1. The essence of the method

The steel specimens kept at a temperature of 20−30 °C aqueous solution of sulfuric acid of copper, sulphuric acid and sodium fluoride in the presence of metallic copper.

The method is rapid as compared to the methods AM and AMU and is used to control the same steel grades that method AMU (p.3.1).

In case of disagreement in the evaluation of metal quality tests carried out by AM.

4.2. Reagents and solutions

The reagent according to claim 2.2 with additions:

sodium fluoride according to GOST 4463;

potassium fluoride according to GOST 20848.

The solution for testing: the water volume (1000±3) cmdissolved sulfuric-acid copper weight (50,0±0,1) g, sodium fluoride mass (128,0±0,1) g, then, in small portions (to prevent heating of the solution) was added sulfuric acid with a volume of (250±1) cm. Pets instead of sodium fluoride mass (128,0±0,1) g to add fluoride potassium mass (177,0±0,1) g.

Preparation of the solution should be carried out in a polyethylene vessel.

4.3. Testing and evaluation of results

4.3.1. The test is performed in a plastic vessel according to claim 2.3.1.

The reaction vessel is filled with a solution for testing at least 20 mm above the sample surface or layer of the chip (copper plates) and close the lid.

4.3.2. The test duration for steels without molybdenum (2,0±0,1) C containing molybdenum (3,0±0,1) h.

4.3.3. Processing of samples after testing is carried out according to claim 2.3.4.

4.3.4. Valid reuse of the solution and metallic copper at PP.2.3.5, 2.3.6.

4.3.5. Detection of intergranular corrosion is carried out by PP.2.3.7 — 2.3.15.

When contention is allowed to inspect curved samples with a magnifying glass with magnification of 16−20.

Evaluation of the results of testing according to claim 2.3.16.

It is allowed to conduct re-trials according to the methods AM and AMU.

5. METHOD WU

5.1. The essence of the method

Samples of steel or alloy is kept in a boiling aqueous solution of ferric sulfate and sulfuric acid.

The method is designed to control steel grade 0ЗХ21Н21М4ГБ and have iron-Nickel alloys grades 06XH28MDT and 03KHN28MDT.

5.2. Reagents and solutions

Sulfuric acid according to GOST 4204 density of 1.83 g/cm, h. d. a. or H. h, solution mass fraction (50,0±0,2)%, a density of 1,395 g/cm.

Iron (III) — sulfuric acid () according to GOST 9485.

Distilled water (pH, chloride content, nitrate, and residue after evaporation — according to GOST 6709).

5.3. Testing and evaluation of results

5.3.1. The tests are carried out in a glass flask or a tank of alloy of iron-Nickel-based, equipped with a reflux condenser. When disagreement in the assessment of the resistance against intergranular corrosion test is carried out in a glass flask.

At the bottom of the reaction vessel placed beads, glass tube or a porcelain boat, on top of which load samples.

In a porcelain mortar to completely grind to a powder of sulphate of iron with a mass of 40 g per 1000 cmvolume of sulfuric acid solution. The resulting powder is poured into the vessel with the sample and then poured into a cold solution of sulfuric acid.

The amount of solution per 1 cmof the surface area of the specimen shall not be less than 5 cm.

Joint download of in vessel samples of steels and alloys of different brands is not allowed.

5.3.2. The duration of exposure in a boiling solution (of 48.00±0,25) h.

Boiling is carried out continuously without heating the refrigerator. When the forced break in the test you must behave as specified in clause 2.3.2.

5.3.3. Detection of intergranular corrosion is carried out according to claim.2.3.7−2.3.15, 2.3.17−2.3.19; evaluation of results of tests carried out on PP.2.3.16, 2.3.20.

Upon detection of intergranular corrosion in alloys of 06XH28MDT and 03KHN28MDT method WU allowed to re-testing method V.

6. METHOD DO

6.1. The essence of the method

The steel samples incubated in a boiling aqueous solution of nitric acid. Method is intended for the control of steel grades 03KH16N15M3, 03KH17N14M3, 03Х18Н11 and 03Х18Н12.

6.2. Reagents and solutions

Nitric acid of high purity according to GOST 11125, solution mass fraction (65,0±0,2)%, a density of 1,391 g/cm; after preparation the solution should be kept at least 24 h.

Distilled water (pH, chloride content, nitrate, and residue after evaporation according to GOST 6709).

6.3. Testing and evaluation of results

6.3.1. Before testing, the samples marked and measured: length, width or diameter and a thickness of not less than three places and determine the average value for each parameter. Measurement error should not exceed 0.1 mm.

The samples were then degreased, rinsed with tap water, rinsed with distilled water, dried and weighed on an analytical balance. The measurement error of the mass should not be more than 0.1 mg.

6.3.2. The tests are carried out in a glass flask with reflux condenser. At the bottom of the flask put beads, glass tube or a porcelain boat, on top of which load samples.

Allowed joint trial in one flask samples of steel only one melting.

6.3.3. Samples poured nitric acid from the calculation of 9−10 cmby 1 cmsample surface. The differences in the evaluation of the resistance against intergranular corrosion, the acid volume was increased to 20 cmby 1 cmsample surface.

6.3.4. Flask samples, filled with a solution of nitric acid, mounted on placed in a fume hood, the heating device providing even heat distribution.

6.3.5. The test is carried out at a weak uniform boiling. Not allowed the evaporation of the solution and separation of nitrogen oxides brown. With the help of indicator paper, you should make sure that the exhaust from the refrigerator pairs do not contain acid. Upon detection of the evaporation of the solution is drained and replaced with fresh.

6.3.6. Testing time is five cycles (of 48.00±0,25) h each.

Permitted by agreement with the consumer for steel grades 03Х18Н11 and 03Х18Н12 after the third cycle, further testing is undertaken if the rate of corrosion in the second and third cycles does not exceed 0.30 mm/year.

6.3.7. After 48 h of boiling, the samples recovered from the flasks, washed with tap water, rinsed with distilled water, dried, weighed and after the change of the solution was charged again.

In case of involuntary interruption of the boiling, the samples recovered from the flasks, washed and dried. The solution can be used to re-load.

6.3.8. For evaluation of intergranular corrosion to determine the corrosion rate (), g/m·h, by the formula (4) or mm/year, according to the formula (5)

(4)

(5)

where is the mass loss of the sample, g;

 — the surface of the test specimen, cm;

 — test duration, h;

 — test steel density, g/cm.

The error in determining the corrosion rate for the recommended sizes of samples (see Annex 2) not more than 0.02 mm/year at a confidence level of 95%.

6.3.9. Samples are considered not satisfactory if the corrosion rate of steels, welded joints, weld metal or weld metal after the second or subsequent cycles greater than 0.5 mm/year, and if the corrosion rate of welded joint is not more than 0.5 mm/year, but or the heat-affected zone, the heat affected zone or the weld metal was subjected to high travelmasti compared to the base metal; inspection of the sample should increase no less than 7 times.

In doubtful cases in assessing the quality of a welded joint carrying out metallographic analysis.

Samples are considered not satisfactory if the average depth of rastravleniya okoloushnoj zone or heat affected zone or weld metal by at least 30 µm more than the base metal.

7. TEST REPORT

The test report should indicate:

1) grade of steel, type of steel, which is made from the sample, labelling;

2) the mode of heat treatment of the sample;

3) test method;

4) test results: patterns of resistance to the ICC, the samples stand against the ICC or the corrosion rate by the method of DU in each of the cycles.

8. SAFETY REQUIREMENTS

Safety requirements when working with the reagents specified in this standard, are the standards for reagents:

nitric acid according to GOST and GOST 4461 11125,

sulfuric acid according to GOST 4204,

copper sulfuric acid according to GOST 4165,

copper sulphate according to GOST 19347,

hydrochloric acid according to GOST 3118,

iron sulfuric acid according to GOST 9485,

sodium fluoride according to GOST 4463,

potassium fluoride according to GOST 20848,

oxalic acid according to GOST 22180,

orthophosphoric acid according to GOST 6552,

ammonium fluoride according to GOST 4518,

the zinc powder according to GOST 12601, class A.

ANNEX 1 (recommended). METHOD IN

ANNEX 1
Recommended

1. The essence of the method

Samples of steel or alloy is kept in a boiling aqueous solution of copper sulphate and sulphuric acid with addition of zinc powder.

The method used to control the alloy 06HN28MDT and 03KHN28MDT.

2. Reagents and solutions

Copper sulfuric acid () according to GOST 4165 or copper sulphate according to GOST 19347.

Sulfuric acid according to GOST 4204 density of 1.83 g/cm, h. d. a. or H. h

Distilled water (pH, chloride content, nitrate, and residue after evaporation according to GOST 6709).

The zinc powder according to GOST 12601, class A.

The solution for the test: water volume (1000±3) cmdissolved sulfate copper weight (110,0±0,2) g, then in small portions was added sulphuric acid volume (55,0±0.3) cm.

3. Testing and evaluation of results

3.1. The test is carried out in a glass flask or a tank of alloy of iron-Nickel-based, equipped with reverse refrigerator. At the bottom of the reaction vessel placed beads, glass tube or a porcelain boat, on top of which load samples. The vessel is then filled with a solution for the test of at least 20 mm above the sample surface and add a zinc powder with a mass of (5,0±0,1) g for every (1000±3) cmvolume of solution.

When violent reaction of hydrogen runs out, the reaction vessel connected to a refrigerator.

3.2. The duration of exposure in solution (of 144.00±0,25) h. the Solution was heated continuously to prevent heating of the refrigerator. When the forced break samples from the reaction vessel is not removed. The test duration is calculated as the total number of hours boiling.

3.3. Processing of samples after testing is carried out according to claim 2.3.4.

3.4. Detection of intergranular corrosion is carried out according to claim.2.3.7−2.3.15, 2.3.17−2.3.19, evaluation of results of tests carried out on PP.2.3.16, 2.3.20 of this standard.

APPENDIX 2 (recommended). METHOD TSK

ANNEX 2
Recommended

1. The essence of the method

The steel samples subjected to anodic etching in 10% aqueous solution of oxalic acid.

Method is used for preliminary evaluation of samples of steel of type 03Х18Н11 be controlled by the method of DU.

2. Reagents and solutions

Oxalic acid (), GOST 22180, h. d. a. or H. h

Distilled water (pH, chloride content, nitrate, and residue after evaporation according to GOST 6709).

The solution for the test: water volume (900±3) cmdissolved oxalic acid mass (100,0±0,1) g.

3. Equipment

Adjustable constant current source with voltage less than 15 V, providing a maximum current of at least 10 A (type of VSA-5K).

The ammeter of the fourth class with a measurement range from 0 to 30 A.

The cathode is in the form of plates or receptacles made of corrosion-resistant steel.

Electrolytic cell made of glass or corrosion-resistant steel.

The terminals for connection of the current source to the cathode cone and the anode.

4. Prototyping-sections

4.1. A workpiece samples-thin sections are cut according to claim 1.1 of this standard subject to the requirements of section 4.2, Appendix 2, subjected to heat treatment according to claim 1.10 and subsequent etching according to claim 1.15.

4.2. From the workpiece in a direction perpendicular to the rolling direction, cold cut cut sample thin section in such a way as not to deform controlled surfaces and to provide the opportunity to assess their condition.

The cutting plane should be the plane of the thin section, the recommended area of the cone not less than 1 cm.

4.3. When the width of the plane of the thin section less than 5 mm sample-sockets are pressed into the plastic or make a cone by any other method that provides high-quality surface preparation.

4.4. Grinding of the sample is performed on grinding the skins from major to minor.

The final operation of manufacture of the cone is polished.

Not allowed heating of the sample-cone.

5. Testing

5.1. Etching of a sample-section taking into account the whole surface immersed in the solution is carried out at a current density of (1,0±0,2)·10A/mfor (1,50±0,01) min.

5.2. The temperature of the solution during etching should be no more than 50 °C, which is achieved by using a water-cooled cell or two cells, one of which is cooled.

You should avoid dipping the clamps in the etching solution.

5.3. At the end of the etching current is turned off, the sample is a thin section is removed from the cell, thoroughly washed in plenty of water and dried.

5.4. In the etching process at the cathode from corrosion-resistant steel may form a yellow-green film that increases the resistance of the cell. The foil must be removed by treating the cathode with nitric acid mass fraction (30±2)%, and then thoroughly rinsing it with water.

5.5. Allowed for the etching of multiple use of a solution of oxalic acid while maintaining its transparency.

6. Classification of etch structures of

6.1. Metallographic study of the structure of the etched surface of the thin section is carried out with increase ; the inspection subjected to the entire surface of the cone.

6.2. The structure of the etching is divided into types:

Grooving structure (Fig.1) the grain boundaries rastravleniya to the formation of the grooves; wherein the one or more grains completely surrounded by the grooves.

Grooving structure

Damn.1

Step structure (Fig.2) the grain boundary are identified either in the form of steps, or in the form of thin lines. Grooves at the grain boundaries do not exist;

Step structure

Damn.2

Intermediate structure (Fig.3) — the boundaries of several grains rastravleniya to the formation of the grooves, but none of the grains completely surrounded by the grooves.

Intermediate structure

Damn.3

The grain pitting I (damn.4) in the structure when you focus on potraviny the plane of the thin section is observed with a lot of small light pitting and a single deep dark grain-boundary pitting are primarily located along the grain boundaries.

Grain-boundary pitting I

 — light pitting;

dark pitting

Damn.4

The grain pitting II (Fig.5) in the structure when you focus on potraviny the plane of the cone there is a significant number of deep, dark grain-boundary pitting and isolated small light pitting.

The grain pitting II

 — light pitting;

dark pitting

Damn.5

6.3. On ProTrainer the cone usually has one of the structures of the etching of grain boundaries and grain-boundary pitting I or II.

Between the intermediate structure and grain-boundary pitting II no sharp difference. At a large gathering on the grain boundary of dark pitting structure may be considered as intermediate with a small restroom grain boundaries.

7. Stupenchataya structure and grain-boundary pitting I indicate the resistance of samples of steel against intergranular corrosion.

Grooving structure — about the propensity of samples of steel to intergranular corrosion.

To confirm the assessment of the steel samples having these two structures, the testing technique do not require.

When the intermediate structure and the grain-boundary pitting II it is necessary to conduct tests on the steel samples according to the method of DU.

Testing is allowed by the method do the steel samples having the grooving structure.

APPENDIX 3 (recommended). METHOD B

APPENDIX 3
Recommended

1. The essence of the method

Steel subjected to anodic etching in an aqueous solution of inhibited sulphuric acid.

The method used to control products and parts fabricated by welding, hot stamping and bending of steel grades 12Х19Н9, 12KH18N9T, 04KH18N10, 08X18H10, 12X18H10T, 08X18H10T, 03Х18Н11, 06KH18N11, 08KH18N12T, 12Х18Н12Т and two layers of steel for these grades.

The weld metal is not subject to control by this method.

2. Equipment

Installation whose schema is shown in hell.6, includes lead container (cathode), represented on the devil.7.

Installation diagram

1 — lead receptacle; 2 — rubber collar; 3 — sample; 4 — a constant current source;
5 — ammeter with a scale division of not more than 0.1 A; 6 — rheostat or a resistance;
7 — switch or key

Damn.6

a — vessel for testing of horizontal surfaces;
b — vessel for testing vertical surfaces; 1 — rubber cuff

Damn.7

3. Reagents and solutions

Sulfuric acid according to GOST 4204 density of 1.83 g/cm, a solution with a mass fraction (60,0±0,2)%.

The urotropine according to GOST 1381 or other inhibitor for sulfuric acid solution with a mass fraction of (0,50±0,05)%.

Distilled water (pH, chloride content, nitrate, and residue after evaporation according to GOST 6709).

Solution for testing contains a solution of hexamine volume (20±1) cmand the acid solution volume (1000±3) cm.

4. Testing and evaluation of results

4.1. The surface areas to be controlled, polished to a roughness of µm. After grinding tests degreased with organic solvents.

4.2. The test is carried out by anodic etching of the controlled areas of the workpiece surface, which are included in a circuit of constant current at a current density of (0,65±0,01)·10A/m. The cathode is a lead vessel (see the devil.7) which is fixed on the controlled surface of the test article or material with rubber cuffs. Poured into a vessel of solution of volume from 3 to 5 cm.

Allowed to produce vessels of another metal, corrosion-resistant in the environment, p.3.

Test temperature (20±10) °C. If you cannot use design vessel given on features.7, is allowed to change the design as applied to controlled products.

4.3. When testing weldments in control of the heat affected zone around the weld. In this case the anode spot is applied so that the edge of the spot seized not more than 1 mm width of weld metal.

In areas subject to control, the strengthening of the seam is removed.

The test is performed on both sides of the seam in a checkerboard pattern. When the weld length up to 2 m heat-affected zone is controlled not less than four points.

4.4. Products having overlapping seams, experiencing all the places of intersection of the seams at the devil.8.

1 — weld; 2 — places of anodic etching

Damn.8

4.5. Duration of test after switching on the current (5,0±0,20) min. At high travelmasti experience and repeat the test duration may be reduced to 1−2 min.

When the test is complete the current is turned off, the vessel and the control surface is washed with water, wiped with filter paper and wipe with ethanol.

4.6. The resistance of steel against intergranular corrosion evaluated by viewing the spot obtained on the surface of the sample or the product after anodic etching, with increase of no less than 20 times (damn.9 and 10).

Magnification 50x

Damn.9

An increase of 50

Damn.10

4.7. A symptom of the tendency to intergranular corrosion is the presence of a continuous mesh in areas of anodic etching (see the devil.9).

In the absence of a continuous mesh banding in areas of anodic etching is not a rejection characteristic (see the devil.10).

4.8. With increased rastravleniya surface areas of anodic etching associated with reduced General corrosion resistance of steel or with very low resistance against intergranular corrosion, repeat tests are carried out on control samples by one of the methods AM and AMU, AMUF.

ANNEX 4 (required). THE CALCULATION FORMULA OF THE RATIO OF DIMENSIONS OF SAMPLES FOR TESTING ACCORDING TO THE METHOD OF DU

ANNEX 4
Mandatory

Flat (6)

Cylindrical (7)

Pipe (8)

Segment (9)

where

 — length, mm;

 — width, mm;

 — thickness, mm;

 — external diameter, mm;

 — arc length, mm;

height, mm.

The length of the arc is determined by the formula ,

where  — coefficient for various values of the width of the segment , is selected according to the annexes 6 and 7 GOST 10006.

Allowed the length to determine with pen and paper. In this case, the error in determining the corrosion rate will not exceed 0.05 mm/year at a confidence level of 95%.

APPENDIX 5 (recommended)

ANNEX 5
Recommended

Table 4

Allowed to bring the thickness or diameter of 3−5 mm, For ferritic steels in the thickness or diameter of not more than 5 mm, for austenitic-martensitic — not more than 3 mm.

For austenitic-martensitic steels, not more than 3 mm.

For segment — arc length ().

The width of the base metal must be at least 5 mm on each side of the seam.

The width of the base metal should be no more than 13 mm on each side of the seam.

APPENDIX 6 (recommended). PHYSICAL METHODS OF CONTROL OF INTERCRYSTALLINE CORROSION

APPENDIX 6
Recommended

1.Ultrasonic method

Ultrasonic method of controlling intergranular corrosion is based on the principle of the dissipation of ultrasonic oscillations on metal surfaces affected by intergranular corrosion. To control intergranular corrosion can be used pulsed ultrasonic device with a set of ultrasound frequencies from 0.5 to 5−10 MHz, for example, US-13, produced by the Chisinau plant. Control should be slanted transducers, sending the metal surface or shear ultrasonic waves.

The transducers should be placed at a distance against each other (not less than 50 mm).

As the contact medium it is advisable to use the transformer oil. The device mode is set for control sample, not subjected to intercrystalline corrosion, so that the signal amplitude was about 40 mm. Depth of corrosion should be evaluated by the change in the amplitude of the ultrasonic signal with regard to its diffusion on metal surfaces affected by intergranular corrosion. For a quantitative estimation of corrosion depth relative developed the ultrasonic method in two variants.

Option 1

Indicators of the degree of dispersion of ultrasonic oscillations, which is determined by the depth of the corroded layer, the accepted relationship of the amplitudes of the echoes in ultrasonic inspection of samples with different depth of corrosion and no corrosion financed by the ultrasound frequency and at a constant gain of the device. These relations are called the coefficients of intergranular corrosion (). They are determined by the following equations

*…
___________________
* The text matches the original. Note the «CODE"


where , , is the amplitude of the signals in the control samples with different depth of intergranular corrosion;

 — the amplitude of the signal in the control sample without corrosion.

Option 2

Indicators of the degree of dispersion of ultrasonic vibrations in the metal, which determines the depth of the corroded layer, the accepted relationship of the amplitudes of the echo signals in the testing of metals at different ultrasound frequencies at a constant gain. The coefficients of intergranular corrosion () in this case determined by the equations

where , , is the amplitude of the signals at a given amplification factor and frequency, respectively ; when the frequency of ultrasonic vibrations is selected in such a way that for maximum destruction metal intergranular corrosion.

The values of the coefficients for the brand and mode of heat treatment, which provide approximately the same grain size, with constant effort ratio are uniquely defined by the depth of intergranular corrosion of metal. Therefore, by setting these coefficients in the control samples with known depth of corrosion, with sufficient accuracy for practice to determine the ultrasonic method for corrosion depth. The value of the coefficient of intergranular corrosion decreases from 1 to 0 with increasing corrosion depth and the sensitivity of the control increases with the ultrasound frequency. It is possible to reliably detect the initial stage of intergranular corrosion in its penetration to a depth of 10 — 25 microns.

It is also possible to estimate the depth of intergranular corrosion by the measurement of the attenuation coefficient of ultrasonic vibrations in the layers of metal corrosion.

2. The method of eddy currents

Method of determining depth of intergranular corrosion eddy currents based on the excitation of eddy currents in the controlled section of the product and a substantial dependence on the conductivity of the material.

The essence of the method consists in the following. The analyzed area of the specimen exposed to the magnetic field coil fed by alternating current. Excited at the same time in the surface layer of the eddy currents create a magnetic field opposite to the field coils. The interaction of the high frequency magnetic field coil with a field of eddy currents leads to a change in impedance of the coil, which causes a change of amplitude and phase fluctuations in the coil.

To control the depth of intergranular corrosion, it is recommended to use eddy current instrument with the frequency of the electromagnetic waves in the range of 500 кГц2 MHz.

To determine the depth of intergranular corrosion it is necessary to pre-build a calibration curve. To construct the curve prepared set of samples of steel of the brand with various depth of corrosion as a result of different time of boiling in the standard solution. The readings for certain areas of these samples are compared with the data of metallographic investigations.

When constructing the calibration graphs, it is desirable to set the device to the optimum mode so that when measurements are used it is possible a large part of the scale unit.

Thus, each calibration curve will be the lower limit of the measurements obtained on the sample that is not subjected to intercrystalline corrosion, and the upper limit of measurement obtained in the control sample with the maximum depth of damage of the surface intercrystalline corrosion for this series of measurements. After building a calibration curve to determine the depth of penetration of intergranular corrosion is reduced to mounting the transducer on the surface of the controlled sample, the scale reading of the instrument and determination of corrosion depth on the calibration curve for a given steel grade.

In the process control, it is recommended to periodically check the installation of the device on the zero sample without corrosion. The limits of measuring the depth of intergranular corrosion of eddy current devices from 10−20 up to 200−500 microns.

3. Color method

Color method of controlling intergranular corrosion based on the capillary penetration of a well-wetting liquid in the defects on the metal surface. The essence of the method lies in the fact that controlled on the surface of the metal layer colored liquid — penetrant indicator (kerosene mass fraction (80,0±0,2)%, turpentine — mass fraction of (20,0±0,2)%, a dye fat-soluble dark red: W (Sudan IV) mass (15,0±0,1) g to (1000±3) cmthe volume of fluid or «Rhodamine» weight (30,0±0,1) g to (1000±3) cmvolume of ethyl technical alcohol).

Under the influence of capillary forces the penetrant penetrates into surface defects.

Some time after the application liquid is removed from the surface of the product. Further, under the action of the absorbent powder which is covered in detail, indicator penetrant out on the surface at the location of the defects. In front of the control surface or the sample is cleaned with gasoline. Then spray or brush apply the penetrant three or four times so that all the controlled surface was thickly covered with them. Small parts or samples immersed in a bath of penetrant.

The process of coating a penetrant lasts 8−10 min.

After coating the penetrant metal surface is washed with an aqueous solution of soda ash mass fraction (5,0±0,1)% and wipe dry. On a dry surface with a spray gun to apply a thin layer of white coating (developer) of the following composition:

water volume (600±1) cm, alcohol volume (400±1) cm, chalk ground (Z00,0±0,1) g to (1000±3) cmthe volume of liquid,

in the case of rodomanova of the dye (1000±3) cmthe volume of the acetone take (250±1) g mass of chalk.

Released from the defects in liquid stain coating in red. With significant depth of intergranular corrosion redness of the coating occurs after 1−2 min the Corrosion is detected as a fine mesh or solid redness coatings for corroded metal surfaces. The degree of redness can roughly estimate the depth of corrosion. If necessary, recording the results of inspection can be used white coating of the following composition:

mass fraction of collodion on fatty alcohol mixture (70,0±0,2)%, mass fraction of benzene (20,0±0,1)%, mass fraction of acetone (10,0±0,1)%, the mass of the dough zinc oxide (50,0±0,1) g to (1000±3) cmvolume of the mixture.

This coating after drying to obtain a thin film.

Working with such a coating must be conducted in a well-ventilated area at strict observance of measures of fire safety.

Color method allows to detect the initial stage of intergranular corrosion in its penetration to a depth of 10−15 microns and more.

APPENDIX 7 (recommended). MODES OF ETCHED THIN SECTIONS AND REAGENTS FOR THE DETECTION OF INTERGRANULAR CORROSION

ANNEX 7
Recommended

Table 5