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ISO 9227 Corrosion Tests in Artificial Atmospheres – Salt Spray Tests

ISO 9227 and its salt spray test play a crucial role in evaluating the corrosion resistance of materials and coatings. By adhering to this standard, industries can ensure that their products withstand harsh corrosive environments, enhancing their durability and reliability. With the help of well-designed salt spray testers and rigorous corrosion testing methods, manufacturers can identify and implement effective corrosion protection strategies, minimizing the impact of corrosion and maximizing customer satisfaction.

ISO 9227 is an international standard that provides guidelines for assessing the corrosion resistance of metallic materials in artificial atmospheres. It establishes a consistent and reproducible test method, ensuring accurate evaluation of a material’s susceptibility to corrosion. This standard has gained widespread acceptance due to its reliability and relevance across industries. One such widely recognized standard is ISO 9227, which outlines the procedures for conducting corrosion tests in artificial atmospheres, specifically the salt spray test.

Equipment Model WEW-YW-90D
Inner Testing Room  900*500*600mm (W*H*D)
Appearance Dimension 1410*1280*880mm (W*H*D)
Laboratory Temperature Neutral Saline Test Method (NSS ACSS) 35C±1C, Acid Saline Test Method (CASS) 50C±1C
Pressure Tank Temperature Neutral saline test method (NSS ACSS) 47C±1C, Acid Saline test method (CASS) 63C±1C
Salt Water Temperature Neutral Saline Test Method (NSS ACSS) 35C±1C, Acid Saline Test Method (CASS) 50C±1C
Laboratory Volume 270L Salt Spray Cabinet
Salt Tank Volume 25L Water Tank
Salt Water Concentration Neutral Saline Test Method (NSS ACSS): Sodium Chloride Concentration 5%; Acid Saline Test Method (CASS); Concentration 5% Sodium Chloride Solution plus 0.26 g Copper Chloride per liter (CuCL2.H20)
Compressed Air Pressure
1.00±0.001kgf/cm2
5.00±1.0011kgf/cm2
Spray Volume 1.0~2.0ml/80cm2·hr (At least 16 hours are collected and the average value is taken)
Laboratory Relative Humidity 85% RH or more
Spray Method Continuous spray (with different controllers for continuous spray and intermittent spray)
Power Requirements AC220V1φ 15A, Salt Spray Cabinet
ISO 9227 Corrosion Tests in Artificial Atmospheres - Salt Spray Tests
To determine the corrosivity of the cabinet, reference specimens made of steel shall be used. It is necessary to verify the cabinet at regular intervals as described in 1.2. to 1.1. 7.1 General 7. Method for Evaluating Cabinet Corrosivity
Note: 1 During permanent operation, a reasonable time period between two checks of the corrosivity of the cab in et is generally co nsider ed to be three months.
As a complement to the reference specimens made of steel, high-purity zinc reference specimens may also be exposed in the tests in order to determine the corrosivity against this metal as described in Annex B.
Note: 2 The corrosivity of th e cabinet verified with stee l or high-purity zinc reference specimens via their mass loss does not guarantee reproducible tim es to th e occurrence of certain corrosion products on coated specimens from industrial production.
To verify the apparatus, use at least four reference specimens of 1,0 mm ± 0,2 mm thickness and 150 mm x 70 mm of CR4-grade steel in accordance with ISO 3574 with an essentially faultless surface and a matt finish (arithmetical mean deviation of the profile Ra; 0,8 ± 0,3 Cut these reference specimens from cold-rolled plates or strips. Alternatively to CR4-grade steel, the following steel grades can be used, DC04 and DCOS according to EN 10130 and UNS Gl0080 according to SAE HS-1086 with reference to the results of the interlaboratory comparison (see Annex F). 7.2 Reference Specimens
Note: 1 “Essentially faultless” m eans free from por es, marks, scratches and any light colouration. Clean the reference specimens carefully, immediately prior to testing. Besides the specifications given in 112 and U cleaning shall eliminate all those traces (dirt, oil or other foreign matter) that can influence the test results.
Thoroughly clean the reference specimens with an appropriate organic so lvent (such as a hydrocarbon with a boiling point between 60°C and 120 °C ) using a clean soft brush or a soft cloth, a non-woven lint-free cloth, that does not leave any remains, or an ultrasonic cleaning device. Carry out th e cleaning in a vessel full of solvent. After cleaning, rinse the reference specimens with fresh solvent and then dry them.
Note: 2 Cleaning with isopropanol can lead to a film of residues on the specimen surface. 
Warning: Most organic solvents are flammable liquids, toxic and irritating. Refer to the safety data sheet for details. Handling of organic solvents shall be restricted to skilled personnel or conducted under their control. Care shall be taken in the disposal of these solvents.
Determine the mass of the referenc e specimens to ±1 mg. Protect one face of the ref e renc e specimens with a removable coating, e.g. an adhesive plastic film. The edges of the refer ence specimens may be protected by the adhesive tape as well.
Position at least four steel reference specimens in four quadrants (if six specimens are available, place them in six different positions including four quadrants) in the zone of the cabinet where the test specimens are placed, with the unprotected face upwards, and at an angle of 20° ± So from the vertical. 7,3 Arrangement of the Reference Specimens
The support for the reference specimens shall be made of, or coated with, inert materials such as plastics. The top of the collecting device should be in level with lower edge of the reference specimens or at the mean reference s pecimen exposure height.
The cabinet should be verified during the testing of test specimens. If this is the case, great care shall be taken that the specimens do not affect each other. Otherwise, the cabinet shall be filled with substitute specimens to maintain the homogeneity of the cabinet. The verification procedure shall be performed using the same settings as for the test runs.
At the end of the test with duration according to Table 2 immediately take the reference specimens out of the test cabinet and remove the protective coating. Remove the corrosion products by mechanical and chemical cleaning, as described in ISO 8407. As one possibility of chemical cleaning, u se a solution of diammonium hydrogen citrate [(NH4hHC6HsO,l (recognized analytical grade) in water with a concentration of 200 gil for 10 min at 23°C. 7,4 Determination of Mass Loss (mass per area)
After each stripping, thoroughly clean the reference specimens at ambient temperature with water, then with ethanol, followed by drying.
Weigh the referenc e 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 u sed during each procedure for the removal of corrosion products.
The cabinet has not performed satisfactorily if the mass loss of steel reference specimen is outside the allowed ranges given in Iahk.1  7.5 Satisfactory Performance of Cabinet
Table 2 Allowed range of mass loss of the steel reference specimens during verification of the corrosivity of the cabinet
Note: Se e Annex B for the use of a zinc refer ence sp ecimen.
salt spray testing
All components in contact with the spray or the test solution shall be made of, or lined with, materials resistant to corrosion by the sprayed solution and which do not influence the corrosivity of the sprayed test solutions. 6.1 Component Protection 6. Apparatus for ISO 9227 Test
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.
The cabinet shall be such that the conditions of homogeneity and distribution of the spray are met. 6.2 Spray Cabinet
Due to the limited capacity of cabinets smaller than 0,4 m 3 , the effect of the loading of the 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 cabinet so that it falls naturally down to them. The upper parts of the cabinet shall be designed so that drops of sprayed solution formed on its surface do not fall on the test specimens.
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 .l.lL3. .
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 diluting salt solution prior to discharging it to the drainage system.
Note: A schematic diagram of one possible design of spray cabinet is shown in Annex A (see Figures A 1 and A..2. ).
The test cabinet shall be maintained at the specified temperature (see 1QJ.) in the zone where the test specimens are placed by the appropriate system. 6.3 Heater and Temperature Control
The device for spraying the salt solution comprises a supply of clean air, of controlled pressure and humidity, a reservoir to contain the solution to be sprayed, and one or more atomizers. 6.4 Spraying Device
The compressed air supplied to the atomizers shall be p asse d through a filter before introduction into the air humidifier to remove all traces of oil or solid matter, and the atomizing pressure shall be at an overpressure of 70 kPa to 170 kPa. The pressure is typically 98 kPa ± 10 kPa but can vary depending on the type of cabinet and ato mizer used.
In order to prevent the eva poration of water from the sprayed droplets (aerosol), the air shall be humidified before entering the atomizer by passing through a suitable humidifier. The humidified air shall be saturated such that the concentration of the fallout solution falls within the specifications of 5..1 . The humidified air shall also be heated such that when mixed with the salt solution and after the adiabatic expansion at the atomizer, there is no significant disturbance of the temperature in the cabinet. The appropriate temperature depends on the pressure used and on the type of atomizer.
Temperature, pr essure or humidification, or a combination thereof, shall be adjusted so th at the rate of collection of the spray in the cabinet and the concentration of the collected spray are kept within the specif ied limits (see 111..3 .). A commonly used humidifier is the saturation tower where temperature and pressure are controllable. Table 1 gives guiding values on temperature and pr ess ure combinations for the saturation tower.
Table 1 Guiding values for the temperature of the hot water in the saturation tower
The atomizers shall be made of inert material. Baffles made of inert material 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 salt solution supplied to the atomizer shall be kept stable to ensure a continuous and uniform fall out as described in 1lL3. . A stable level of spraying can be achieved by either controlling the level of salt solution in the reservoir or restricting the flow of salt solution to the atomizer such that a continuous spray is achieved.
Distilled or deionized water with a conductivity not higher than 20 at 25 ‘C shall be used for humidification of spray air.
At least two collecting devices shall be used to check the homogeneity of the spraying of the cabinet. 6.5 Collecting Devices
Suitable funnels shall be made of chemically inert material, with the stems inserted into graduated cylinders or other similar containers and have a diameter of 100 mm, which corresponds to a collecting area of approximately 80 cmz’ The collecting devices shall be placed in the zone of the cabinet where the test specimens are placed. They shall be placed so that only mist, and not liquid falling from specimens or from parts of the cabinet, is collected.
The collecting devices shall be placed as follows.
a) During the test, two collecting devices should be placed at central points in the zone (see Annex E for an example).
b) For calibration purposes, the collection rate of the cabinetshall be verified with at least six collecting devices, which are placed at the four corners and two central points of the zone (see Annex E for an example). This verification is done without te st specimens in the cabinet, but preferably with substitute specimens (see also 1ll.2 ). It is recommended to perform it after installation, a move, modifications, adjustments or repair of the cabinet, after detecting nonconformities of the sp ray collection rate during running tests [ see a)]. and after idl e periods longer than four weeks.
c) If the collecting devices cannot be placed at four corners and/or at the central two points in the zone, they may be placed at another point by agreement between the interested parties. The number of collecting devices placed may also be changed according to the size of the cabinet by the agreement between the interested parties. In those cases, it shall be sta ted in the test report.
Note: During permanent operation, a reasonable time period of the ver ifi cation of the collection rate of the cabinet is generally considered to be three months.
When nonconforming spray collection rates are found during verification [see b)]. the cabinet shall be adjusted or the test specimens shall not be placed in the nonconforming area.
If the cabinet has been used once for an AASS or CASS test, or has been used for any other purpose with a solution differing from that specified for the NSS test, it shall not be used for the NSS test until a thorough cleaning procedure has been completed and the pH of collected solution has been verified by th e method in .5..2…2 and the corrosivity of the cabinet verified by the method in Clallse 7 to not be significantly affected by pr evious tests. 6.6 Re-use
Additionally, it is recommended to check that the copper concentration in the collected solution is below the allowed limit of 2,5 mg/I (see 5.1), better below 0,5 mg/I, when the cabinet was previously used for CASS, but should now be used for AASS or NSS.
Note: It is very difficu lt to clean a cabinet suffici ent ly that was once used for AASS or CASS testing so that it can be used for an NSS test.
This ISO 9227 document can involve hazardous materials, operations and equipment. This document does not purport to address all of the safety concerns, if any, associated with its use. 4. Principle of ISO 9227
It is the responsibility of the user of this document to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
The NSS test is the test method in which a neutral approximate 5 % sodium chloride solution is atomized under a controlled environment.
The AASS test is the test method in which an approximate 5 % sodium chloride solution acidified by the addition of acetic acid is atomized under a controlled environment.
The CASS test is the test method in which an approximate 5 % sodium chloride solution acidified by the addition acetic acid and with the addition of copper(lI) chloride is atomized under a controlled environment.
salt spray fog apparatus
Dissolve a sufficient mass of sodium chloride in distilled or deionized water with a conductivity not higher than 20 at 25 °C to produce a concentration in a range between 45 gil and 55 gil. The sodium chloride concentration of the sprayed solution collected shall be 50 gil ± 5 gil. The specific gravity range for a 50 gil ± 5 gil solution is 1,029 to 1.036 at 25 ° C. 5,1 Preparation of the Sodium Chloride Solution 5. Test Solutions
The sodium chloride shall not contain a mass fraction of the heavy metals 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: Anti-caking agents added to the sodium chloride can act as corrosion inhibitor s or accelerators. A useful sodium chloride salt grade is a grade named Ph. Eur/USP or liS, ACS.
5.2.1 pH of the Salt Solution 5.2 Preparation of Each Test Solution With pH Adjustment
Adjust the pH of the salt solution to the desired value on the basis of the pH of the sprayed solution collected.
5.2.2 Neutral Salt Spray Test
Adjust the pH of the salt solution (see .5..1 ) so that the pH of the sprayed solution collected within the test cabinet ( .6..2. and .u.s. ) is 6,5 to 7,2 at 25 °C ± 2 0 c. Check the pH using electrometric measurement.
Measurements of pH shall be done using electrodes suitable for measuring in weakly buffered sodium chloride solutions in distilled or deionized water. Make any necessary corrections by adding hydrochloric acid, sodium hydroxide or sodium bicarbonate solution of analytical grade.
Warning: Hydrochloric acid (CAS Registry Number®l) 7647-01-0) solution is toxic, corrosive, irritating and very toxic to aquatic life. Refer to the safety data sheet for details. Handling of hydrochloric acid solution shall be restricted to skilled personnel or conducted under their control. Care shall be taken in the disposal of this solution.
Warning: Sodium hydroxide (CAS 1310-73-2) solution is toxic, corrosive and irritating. Refer to the safety data sheet for details. Handling of sodium hydroxide solution shall be restricted to skilled personnel or conducted under their control. Care shall be taken in the disposal of this solution.
Note: Possible changes in pH can result from loss of carbon dioxide in 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 above 35 °C before it is placed in the apparatus. or by making the solution using freshly boiled water.
5.2.3 Acetic Acid Salt Spray Test
Add a sufficient amount of glacial acetic acid not less than 99,7 % of mass fraction or diluted acetic acid more than 10 % of mass fraction to the salt solution (see .5..1 ) to ensure that the pH of samples of sprayed solution collected in the test cabinet ( .6..2. and .u.s. ) is between 3,1 and 3,3 at 25 °C ± 2 0 c. Take the added volume of acetic acid into account when making up the initial sodium chloride solution. 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. Check the pH using electrometric measurement. Measurements of pH shall be done using electrodes suitable for measuring in weakly buffered sodium chloride solutions in distilled or deionized water. Make any necessary corrections by adding acetic acid, sodium hydroxide, or sodium bicarbonate of analytical grade.
Warning: Glacial acetic acid (CAS 64-19-7) is a flammable liquid, toxic, corrosive and irritating.
Refer to the safety data sheet for details. Handling of glacial acetic acid shall be restricted to skilled personnel or conducted under their control. Care shall be taken in the disposal of this solution.
5.2.4 Copper·accelerated Acetic Acid Salt Spray Test
Dissolve a sufficient mass of copper(lI) chloride dihydrate (CuCI 2 ·2H 2 0) not less than 99.0 % of mass fraction in the salt solution (5.1) to produce a concentration of 0,26 gil ± 0,02 gil [equivalent to (0,205 ± 0,015) g of CuCl 2 per litre].
Warning: Copper(lJ) chloride dihydrate (CAS 10125-13-0) is toxic, corrosive, irritating and very toxic to aquatic life. Refer to the safety data sheetfor details. Handling of copper(lJ) chloride dihydrate shall be restricted to skilled personnel or conducted under their control. Care shall be taken in the disposal of this solution.
Adjust the pH using the procedures described in .5..2…3. .
If necessary, filter the solution before placing it in the reservoir of the apparatus, to remove any solid matter which can block the apertures of the spraying device. 5.3 Filtration
The number and type of test specimens. their shape and their dimensions shall be selected in accordance with the specification for the material or product being tested. When not specified, these parameters shall be mutually agreed between the interested parties. Unless otherwise specified or agreed, test specimens with an organic coating to be tested shall be made from burnished steel conforming to ISO 1514, and of approximate dimensions 150 mm x 100 mm x 1 mm. Annex C describes how test specimens with organic coatings shall be prepared for testing. Annex D gives supplementary information needed for testing test specimens with organic coatings. 8. Test Specimens
The test specimens shall be thoroughly cleaned before testing, if not otherwise specified. 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 can attack the surface of the specimens. Care shall be taken that test specimens are not re-contaminated after cleaning by careless handling.
If the test specimens are cut out from a larger coated article, cutting shall be carried out in such a way that the coating is not damaged in the area adjacent to the cut. 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.
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