ISO 7253 is a globally recognized standard for evaluating the resistance of paints and varnishes to neutral salt spray. By conducting corrosion tests according to this standard, manufacturers can ensure the durability and performance of their coatings. Utilizing salt spray chambers and testing equipment enables accurate assessment of a coating’s resistance to corrosion, leading to improved product quality and customer satisfaction. ISO 7253 is an international standard that specifies a test method for evaluating the resistance of paints and varnishes to neutral salt spray (fog).
ISO 7253 provides a standardized method for evaluating the performance of paints and varnishes when subjected to salt spray environments. It simulates the effects of long-term exposure to corrosion-inducing conditions such as saltwater, rain, and humidity. Compliance with ISO 7253 ensures that coatings meet the required standards, guaranteeing their performance and durability. This test is crucial in determining the corrosion resistance of coatings and ensuring their durability in various environments.
| Mode and Description |
WEW-YW-60D |
WEW-YW-90D |
WEW-YW-110D |
| Inner Dimension(mm) |
600*450*400 |
900*600*500 |
1000*750*500 |
| Outer Dimension(mm) |
1070*600*1180 |
1410*880*1280 |
1600*1050*1200 |
| Test Room Size (Liters) |
108
Liters |
270
Liters |
420
Liters |
| Power Supply |
AC
220V, 50Hz |
AC
220V, 50Hz |
AC
220V, 50Hz |
| Power Current |
1Phase,
1.5 kW |
1Phase,
2.0 kW |
1Phase,
2.5 kW |
| Lid Opening Method |
Manual
Opening |
Manual
Opening |
Manual
Opening |
| Brine Tank Volume |
15
Literes |
25
Literes |
30
Literes |
| Test Room Temp Range |
Ambient
Temperature +5℃ – +30℃, Ventilation is recommended, if the temperature
exceeds +30℃, it is recommended to adjust the room temperature by suitable
means. Ambient humidity should be controlled below 80%RH. |
| Test Room Temp Range |
RT+10℃
– +55℃ |
RT+10℃
– +55℃ |
RT+10℃
– +55℃ |
| Saturated Barrel |
RT+10℃
– +70℃ (Purpose: Heating and filtering of compressed air to reduce nozzle
crystallisation.) |
| Temp Performance |
Temperature
Uniformity: ≤2℃, |
Temperature
Fluctuation: ≤ ±0.5°C |
Temperature
Uniformity: ≤2℃, |
| Salt Mist Settling Rate |
1~2 ml/80 cm2/h (Take 16 Hours To Test The
Average Value)｜1~2 ml/80 cm2/h |
| Spray Method |
Continuous,
Intermittent, |
Programmable
Tests |
Continuous,
Intermittent, |
| Testing Type |
NSS,
AASS |
NSS,
AASS,CASS |
NSS,
CASS |
| Safety Devices |
Low Water Level Alarm｜Over-Temperature Alarm
(Mechanical Over-Temperature Protection + Electronic Over-Temperature
Protection Double Over-Temperature Protection) |
| Air Requirements |
Inlet
Pressure Above 0.4Mp. |
Two-Stage
Pressure Regulation. |
Spray
Pressure 0.07~0.17mp (Adjustable) |
| Sample Holder |
One
Set Each Of V-Groove And O-Round Bar (Combined To Form An Angle Of 20°±5%). |
| Standard Configuration |
1 Set
Of V-Type/O-Type Shelves, 2 Bottles Of Test Drug Sodium Chloride
(500g/Bottle), 1 Plastic Anti-Rust Bucket (5l Capacity), 1 Nozzle |
| 5.1The test solution shall be prepared by
dissolving sodium chloride in water of at least grade 3 purity as defined
inISO 3696 to produce a concentration of (50±5) gl.The sodium chloride shall
be white, of minimum assay 99,6 %(m/m), and substantially free from copper
and nickel; it shall contain not more than 0,1 %(m m) of sodium iodide. lfthe
pH of the solution is outside the range 6,0 to 7,0, the presence of
undesirable impurities in the salt or the wateror both shall be investigated. |
5 Test Solution |
| 5.2 The pH of the test solution (5.1) shall be adjusted so
that the pH of sprayed solution collected within the testcabinet (see clause
6) shall be between 6,5 and 7,2.Any necessary adjustment to the pH shall be
made byadditions of solutions of either hydrochloric acid or sodium
bicarbonate of analytical grade. |
| Note 2: Attention is drawn to the possible changes in pH
resulting from loss of carbon dioxide from the test solution where it is
sprayed.Such changes may be avoided by reducing the carbon dioxide content of
the solution by, for example, heating it to atemperature above 35 *C before
it is placed in the apparatus or by making the solution from freshly boiled
water. |
| 5.3 The test solution shall be filtered before it is placed in
the reservoir of the apparatus, in order to remove anysolid matter which
might block the nozzle(s) of the spraying device. |
| Ordinary laboratory apparatus and glassware, together with the
following: |
6 Apparatus |
| 6.1 A spray cabinet, made of,or lined with, material resistant
to corrosion by the spray and with a roof whichprevents condensed moisture
dripping on to the test panels. The cabinet shall have a capacity of not less
than0,4 m3 since, with smaller volumes, difficulties are experienced in
ensuring even distribution of spray. |
| The size and shape of the cabinet shall be such that the
quantity of solution colected in the spray-collecting devices(6.4) is within
the limits stated in 10.2. |
| Cabinets with a volume greater than 2 m3 will be difficult to
operate unless careful consideration is given to theirdesign and
construction. Factors which shall be taken into consideration are given in
annex B. |
| 6.2 Adjustable heater, adequate to maintain the cabinet and
its contents at the specified temperature (see 10.1).The temperature shall be
controlled by a thermostat element placed within the cabinet at least 100 mm
from thewalls. A thermometer, capable of being read from the outside, shall
be placed wholly within the cabinet at least100 mm from the walls, roof or
floor. |
| 6.3 Spraying device, comprising a supply of clean compressed
air of constant pressure and humidity, a resevoir containing the solution to
be sprayed and one or more spray nozzles made of material resistant to the
solution. |
| The compressed air supply to each spray nozzle shall be passed
through a flter to remove all traces of oil or solidmatter and shall be at a
pressure of 70 kPa to 170 kPa2). in order to prevent evaporation of the spray
droplets, theair shall be humidified before entering each nozzle by passage
through a saturation column containing water of atleast grade 3 purity as
defined in IS0 3696 at a temperature several degrees Celsius higher than that
of the cabinet.The actual temperature of the water will depend on the
pressure used and on the type of spray nozzle, and sha be adjusted so that
the rate of collection of spray in the cabinet and the sodium chloride
concentration of the spraycollected are kept within the specified limits (see
10.2). |
| The reservoir containing the test solution shall be made of
material resistant to the solution and shall be providedwith a means of
delivering a constant volume of solution to the spray nozzles at all times. |
| The spray nozzles shall be made of inert material, for example
glass or plastic. |
| The cabinet shall be vented to ensure that there is no build
up of pressure within the cabinet and in such a way thatthe environment
outside the cabinet does not influence that inside the cabinet. |
| Note3 Baffies may be used to prevent direct impingement of
spray on the test panels, and the use of adjustable baffies ishelpful in
obtaining uniform distribution of spray throughout the cabinet. |
| 6.4 Spray-collecting devices, of chemically inert material
(see Note 4).The collecting devices shall be placed inthe zone of the cabinet
where the test panels are placed, at least one close to a spray nozzle and
one remote froma spray nozzle. They shall be placed so that only spray is
colected, and not liquid dripping from test panels or partsof the holders or
cabinet. The number of collecting devices shall be at least twice the number
of spray nozzles. |
| Note 4: Glass or plastic funnels with their stems inserted
into graduated cylinders have been found to be suitable
collectingdevices.Funnels with a diameter of 100 mm have a collecting area of
approximately 80 cm?. |
| 6.5 Test panel holders, capable of supporting the test panels
at an angle of between 15° and 25′ to the vertical, normally racks made of
inert non-metallic material such as glass, plastic or suitably coated wood.
Exceptionally , if itis necessary to suspend the test panels, the material
used shall be synthetic fibre, cotton thread or another inertinsulating
material, but on no account metalic material. The test panels may be located
at different levels in thecabinet but they shall be positioned so that the
solution cannot drip from panels or holders at one level on to otherpanels
below. |
| 6.6 lf the equipment has been used for a spray test, or for
any other purpose, with a solution differing from thatspecified for this
test, it shall be thoroughly cleaned before use. |
| 6.7Calibration of the equipment shall be carried out as
specified in annex C. |
In addition to meeting the requirements of coating or product specifications, the determination of the resistance of coatings to neutral salt spray (fog) plays a crucial role in assessing the durability and quality of paints, varnishes, and related products. By subjecting these coatings to the intense corrosive and degrading effects of salt spray, this method enables manufacturers, suppliers, and customers to evaluate their performance and suitability for various applications and environments.
The neutral salt spray test serves as a valuable tool in predicting how coatings will withstand the challenges posed by harsh weather conditions, including coastal areas where high levels of salt and humidity prevail. This standardized procedure not only aids in comparing the performance of different coatings but also assists in identifying potential weaknesses, enabling further improvements in formulation and application techniques. By incorporating this method into the broader range of standards on sampling and testing, this International Standard enhances the reliability and consistency of assessments, contributing to the overall advancement of the paints, varnishes, and related industries.
| Take a representative sample of the product to be tested (or of
each product in the case of a multi-coat system) as described in lSO 1512. |
7 Sampling |
| Examine and prepare
the sample for testing, as described in ISO 1513. |
| Unless otherwise specified or agreed, the test panels shall be
of burnished steel complying with ISO 1514, and ofapproximate dimensions 150
mm x 100 mm x 1 mm. |
8.1 Material and
Dimensions |
8 Test panels |
| Unless otherwise specified, prepare each test panel in
accordance with lSO 1514 and then coat it by the specifiedmethod with the
product or system under test. |
8.2 Preparation and coating
of panels |
| Uniess otherwise specified, the back and edges of the panel
shall also be coated with the product or system undertest. |
| lf the coating on the back and edges of the panel differs from
that of the product under test, it shall have a corrosionresistance greater
than that of the product under test. |
| Dry (or stove) and age (if applicable) each coated test panel
for the specified time under the specified conditions,and,unless otherwise
specified, condition them at a temperature of (23 ±2)°C and a relative
humidity of (50 ±5) %for at least 16 h, with free circulation of air and
without exposing them to direct sunlight. The test procedure shallthen be
carried out as soon as possible. |
8.3 Drying and
conditioning |
| Determine the thickness, in micrometres, of the dried coating by
one of the non-destructive procedures described inISO 2808. |
8.4 Thickness of
coating |
| All scratches shall be at least 25 mm from each other and from
any edge of the test panel.lf specified, make a straight scratch or scribed
mark through the coating to the substrate. |
8.5 Preparation of scratches |
| To apply the scratch, use a scratch instrument with a hard
tip.The scratch shall have either parallel sides or anupwards-broadening
cross-section which shows a width of 0,3 mm to 1,0 mm of the metallic
substrate，unlessotherwise agreed. |
| One or two scratches may be applied. The scratch(es) shall be
parallel to the longer edge of the test panel, unlessotherwise agreed.
Cutting the scratch with a knife is not allowed. |
| For aluminium panels,two scratches shall be made which are
perpendicular to, but do not intersect, each other.One scratch shall be
parallel to the rolling direction and the other at right angles. |
| Note 5: lf zinc- or zinc-alloy-coated steel is used as a test
panel the intention is that the scratch should be to the zinc coating, and
not further, to the steel, unless otherwise agreed. |
| 9.1
Place the panels in the cabinet such that they are not in the direct line of
travel of spray from a spray nozzle. |
9 Method of Exposure
Of Test Panels |
| 9.2 Each test surace shall be placed in the cabinet facing
upwards at an angle of between 15° and 25° to thevertical. |
| Note6 The angle at which each panel is exposed in the cabinet is
very important. |
| By agreement between the interested parties,it is sometimes
necessary to expose painted components of differentshapes. When such tests
are conducted, it is of particular importance to expose the shaped components
in theirnormal attitude in use.Within this restriction the component shall be
placed so as to minimize the disruption of flow.Furthermore, other test
panels and components cannot be tested at the same time if the shape of the
paintedcomponent interferes with the general direction of flow. |
| The degree of film breakdown at different angles of orientation
may vary, and due consideration shall be given tothis in the interpretation
of the results. |
| 9.3 Arrange the panels so that they do not come into contact
with one another or with the cabinet and so that thesurfaces to be tested are
exposed to the spray only where it is settling freely. |
| 10.1 The measured temperature inside the spray cabinet shall be
(35±2) ℃. |
10 Operating Conditions |
| 10.2 The average rate of collection of spray solution, measured
over a minimum period of 24 h, shall be 1 ml/h to2,5 ml/h for a horizontal
spray-collecting device of area 80 cm2. |
| This solution collected shall have a sodium chloride
concentration of (50±10) g/l and a pH of 6,5 to 7,2(see 5.2). |
| 10.3 Test solution which has been sprayed shall not be re-used. |
| Carry
out the determination in duplicate, unless otherwise agreed. |
11 Procedure |
| 11.1 Set up the apparatus and adjust it to meet the conditions
specified in clause 10. |
| 11.2 Arrange the test panels in the cabinet as described in
clause 9. |
| 11.3 Close the cabinet and start the flow of the test solution
through the spray nozzle(s). Continuously spraythroughout the prescribed test
period, except for a short daily interruption (see clause 12) to inspect,
re-arrange orremove test panels, to check and replenish the solution in the
reservoir and to check that the conditions specified inclause 10 are still
being met. |
| Make periodic examinations of the panels, taking care not to
damage the surfaces under test. The panels shall beassessed as quickly as
possible and the cabinet shall be turned off for no more than 30 min in any
24 h. Do notallow the panels to dry. |
12 Examination of Test
Panels |
| Whenever possible, the examination shall be made at the same
time of day. |
| At the end of the specified test period, remove the panels from
the apparatus and rinse with clean, warm water toremove residues of test
solution from the surface. Immediately dry the panel and examine the test
surfaces forsigns of deterioration, for example blistering, rusting or creep
of corrosion from the scratch(es), in accordance withlSO 4628, parts 1 to 5
[see annex A, item g)]. |
| lf required, keep the panels in the standard conditions defined
in IS0 3270 for the specified period and then re-examine the test surfaces
for deterioration. |
| lf it is required to examine the substrate for signs of attack,
remove the coating by the specified method. |
| No relevant precision data are currently available. |
13 Precision |
| ISO/TC 35 intends to obtain precision data for all relevant
standards, including IS0 7253. When precision data areavailable these will be
incorporated in the standard. |
| Users of this standard should be aware that, because of the
subjective nature of the assessment of the deterioration of the
coating，precision will depend upon a number of factors.These include the
evaluation method, the preparation of the test panels, the thickness of the
coating, the drying and conditioning of the test panels and the preparation
of the scratch(es). |
| However, the method has been found to be useful in comparing the
salt spray resistance of different coatings. lt ismost useful in providing
relative ratings for a series of coated panels exhibiting significant
differences in salt sprayresistance. |
