ISO14993金属和合金的腐蚀.在盐雾、干燥和潮湿条件下循环暴露的加速试验
ISO14993金属和合金的腐蚀试验箱
Corrosion of metals and alloys — Accelerated testing
involving cyclic exposure to salt mist, dry and wet
conditions
WARNING — This document may involve hazardous materials, operations and equipment. It does
not purport to address all of the safety problems associated with its use. It is the responsibility
of the user of this document to establish appropriate safety and health practices.
1 Scope
This document specifies the apparatus and test procedure to be used in conducting accelerated
corrosion tests for the comparative evaluation of metallic materials with or without permanent
corrosion protection or temporary corrosion protection in salt-contaminated outdoor environments.
The test involves cyclic exposure of the specimens to neutral salt mist, “dry” and “wet” conditions. The
type of test specimen and the exposure period are not specified.
The particular advantages of this test over common accelerated tests such as the neutral salt spray
(NSS) test lie in its ability to better reproduce the corrosion that occurs in outdoor salt-contaminated
environments.
This document is applicable to
—
metals and their alloys,
—
metallic coatings (anodic and cathodic),
—
conversion coatings,
—
anodic oxide coatings, and
—
organic coatings on metallic materials.
NOTE
Methods of test for coatings to determine their resistance, in the presence of scribe marks through
to the substrate, to various cyclic corrosion conditions which include the condensation of water on the test
specimens during periods of humidity are given in ISO 11997-1.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 1514, Paints and varnishes — Standard panels for testing
ISO 2808, Paints and varnishes — Determination of film thickness
ISO 4623-2:2016, Paints and varnishes — Determination of resistance to filiform corrosion — Part 2:
Aluminium substrates
ISO 8044, Corrosion of metals and alloys — Basic terms and definitions
ISO 17872, Paints and varnishes — Guidelines for the introduction of scribe marks through coatings on
metallic panels for corrosion testing
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 8044 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
—
ISO Online browsing platform: available a
3.1
reference material
material with known test performance
3.2
reference specimen
portion of the reference material (3.1) that is to be exposed with the intention to check the reproducibility
and repeatability of the test results for the test cabinet in use
3.3
test specimen
specific portion of the samples upon which the testing is to be performed
3.4
substitute specimen
specimen made of inert materials (such as plastic or glass) used for the substitute of a test specimen (3.3)
4 Test solution
4.1 General
Instructions for the preparation and use of a neutral sodium chloride solution are given in 4.2 and 4.3.
4.2 Preparation of the sodium chloride solution
Dissolve a sufficient mass of sodium chloride in distilled or deionized water with a conductivity no
higher than 20 μS/cm at 25 °C ± 2 °C to produce a concentration of 50 g/l ± 5 g/l. The sodium chloride
concentration of the sprayed solution collected shall be 50 g/l ± 5 g/l. The specific gravity range for a
50 g/l ± 5 g/l solution is 1,029 to 1,036 at 25 °C.
The sodium chloride shall not contain a mass fraction of the heavy metals of copper (Cu), nickel (Ni) and
lead (Pb) in total more than 0,005 %. It shall not contain a mass fraction of sodium iodide more than
0,1 % and a mass fraction of total impurities more than 0,5 %, calculated for dry salt.
NOTE
Sodium chloride with anti-caking agents can act as corrosion inhibitors or accelerators. A useful
sodium chloride salt grade is a grade named Ph. Eur/USP or JIS, ACS.
4.3 pH adjustment
Adjust the pH of the salt solution so that the pH of the sprayed solution collected within the test cabinet
is 6,5 to 7,2 at 25 °C ± 2 °C. Check the pH using electrometric measurement. Measurements of pH
shall be done using electrode suitable for measuring in weakly buffered sodium chloride solutions in
deionized water. Make any necessary corrections by adding hydrochloric acid, sodium hydroxide or
sodium bicarbonate solution of analytical grade.
NOTE
Possible changes in pH can result from loss of carbon dioxide from the solution when it is sprayed.
Such changes can be avoided by reducing the carbon dioxide content of the solution by, for example, heating it
to a temperature greater than 35 °C before it is placed in the apparatus, or by making the solution from freshly
boiled water.
5 Apparatus
5.1 Component protection
All components in contact with the salt mist spray or the test solution shall be made of, or lined with,
materials which are resistant to corrosion by the test solution and which do not influence the corrosivity
of the sprayed test solution.
The supports for the test specimen shall be constructed such that different substrate types do not
influence each other. It shall also be constructed so that the supports themselves do not influence the
test specimens.
5.2 Exposure equipment
5.2.1 Test cabinet, that meets the conditions of homogeneity and distribution of the spray. Due to the
limited capacity of test cabinets smaller than 0,4 m3, the effect of the loading of the test cabinet on the
distribution of the spray and temperature shall be carefully considered. The solution shall not be sprayed
directly onto test specimens but rather spread throughout the test cabinet so that it falls naturally down
on them. The upper parts of the test 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 test cabinet shall be such that during periods of exposure to salt mist spray,
the collection rate of solution in the test cabinet is within the limits specified in 8.2.
NOTE
A schematic diagram of one possible design of test cabinet and associated apparatus for salt mist
cyclic corrosion testing is shown in Annex A.
5.2.2 Humidity and temperature control system, that maintains the test cabinet and its contents
at the specified temperature and humidity (see 8.1). The temperature shall be measured at a position at
least 100 mm from walls and radiant heat sources.