ISO 11845:2020 pdf download Corrosion of metals and alloys — General principles for corrosion testing
4.4 The test conditions should, as far as possible, be matched to the practical conditions under which the material and the corrosive media will be used, except for short-duration tests as detailed in 4.5. This applies:
a) to the material, in relation to its shape, surface condition, grain structure, etc., for details see Clause 5;
b) to the corrosive medium, in relation to concentration, temperatures, etc., for details see Clause 7.
4.5 In the case of short-duration corrosion tests, the object is to achieve usable results in the shortest possible time by intensifying the attack conditions. However, intensification of the attack conditions, e.g. by increasing the temperature or concentration of the corrosive medium, often gives results that do not correspond to behaviour under practical conditions. Care shall therefore be exercised when applying such results in practice.
4.6 Particular care is necessary when applying the results of accelerated corrosion tests to practical conditions since, with this type of corrosion test, corrosion media differing from those occurring in practice are often used.
4.7 For the specific purpose, the material, the corrosive medium, the ratio of solution volume to surface area, the surface area, the temperature, the agitation, the test duration, the evaluation, and the corrosion form should be in accordance with the International Standards given in Annex A. 5 Materials
5.1 Test specimens shall be clearly identified. The following information should be given, when applicable:
a) chemical composition of the material and the appropriate designation, according to the relevant international, regional or national standards;
b) condition of the material and fabrication details (e.g. presence of welds, sand cast, gravity die cast, pressure die cast, hot rolled, cold rolled, forged, heat-treatment, whether naturally or artificially aged);
c) form of material (sheet, wire, tube, solid bars or similar);
d) position and orientation of the specimens in the original material (with a sketch if necessary);
e) dimensions (exact size, shape, area) and mass of specimens;
f) condition of the surface of the material (with or without rolling skin, thickness of rolling skin, pickled, ground, polished, or other pretreatment);
g) mechanical properties of the material;
h) structure of the material, including any chemical or mechanical pretreatment;
i) protective layers and coatings (type, composition and thickness).
5.2 The method of producing the specimens from the test piece should be documented. Specimens should preferably be taken from the test piece in such a manner as to exclude the effect of any significant additional mechanical cold working and any substantial temperature rise at the cut edges during machining. Any burr at the cut edges produced when the specimen is obtained should be removed. In general, it is necessary to protect the edges where it is likely that unwanted effects on the corrosion behaviour of the material being tested should originate at the edges (e.g. in the case of coated specimens).
5.3 In the case of corrosion tests under conditions close to those obtained in practice, the surface condition of the specimens should be the same as that found in practical application.
5.4 In general, specimens should be cleaned and degreased. The choice of suitable cleaning or degreasing agents depends on the material being tested. Only products that do not alter the surface of the part being tested should be used. In most cases, organic solvents are used. The cleaning agent used should be reported.
5.5 If the specimen surface has to be mechanically pretreated, this should preferably be done by grinding, with each step removing damage from the previous step. The grade of the final abrasive used should be reported. Machining is preferable to grinding for soft metals.
5.6 Specimens should be clearly marked, for example by stamping with numbers or letters. Since the mechanical stress resulting from stamping with numbers or letters can initiate local corrosion, in the case of particularly sensitive materials, and under defined test conditions, it is desirable to use a method of marking which does not involve any cold working, e.g. electro-mechanical marking or notching of specimens. It should be necessary to carry out heat treatment of the specimen after marking.
6 Corrosive medium
6.1 The corrosive medium shall be clearly described. In particular, the origin, composition, method of preparation and condition of the corrosive medium should be quoted.
6.2 The information on the origin of the corrosive medium should state whether the solutions used are of natural origin, normally occurring in technical processes or whether they are specially manufactured.
6.3 Where the quantitative chemical composition of the medium is not known, it should be determined by analysis and the analysis should also take into account small amounts of admixtures or impurities.ISO 11845:2020 pdf download