What Is Salt Spray?
The salt fog test is an experiment in which corrosion resistance is evaluated in an accelerated manner by exposing the sample to salt solution fog in a controlled cabin. It provides comparative data in a short time on corrosion behavior over many years in the natural atmosphere.
Purpose of Salt Spray
The aim is to determine how long a coating or material provides protection in a corrosive environment and to compare different coating systems under the same conditions. The test does not give an absolute lifespan estimate; Used for quality control and specification compliance.
Which Products Is Salt Spray Applied To?
- Painted and coated metal parts
- Galvanised and zinc coatings
- Automotive body and fasteners
- White goods sheet metal components
- Hardware and fasteners used outdoors
In Which Sectors Is Salt Spray Used?
Standards Related to Salt Spray
- ASTM B117tuz sisi (salt spray) korozyon testi test
- ISO 9227tuz sisi korozyon testi test
- ASTM G85modified salt fog (cyclic) test test
- ISO 16701cyclic corrosion test test
- SAE J2334cyclic laboratory corrosion testing test
- VDA 233-102cyclic corrosion testing in automotive test
- ASTM G48pitting and crevice corrosion in stainless steels test
- ISO 6270strength in condensation environment test
Salt Spray Conditions
- Solution
- 5% NaCl (by mass), pH 6.5–7.2 for ASTM B117
- cabin temperature
- 35 °C ± 2 °C (neutral salt fog)
- Sis toplama debisi
- 80 cm² alanda 1,0–2,0 mL/saat
- sample angle
- 15°–30° from vertical
Equipment for Salt Spray
- Salt fog chamber
- Atomizer and compressed air conditioning
- pH and conductivity meter
- Fog collection funnels
Sample Requirements for Salt Spray
- At least three samples are recommended
- The sample surface must be clean and dry before testing.
- Cut edges must be properly masked
- Dimensions must comply with the cabinet shelf layout
Duration of Salt Spray
According to the specification, it is applied in stages such as 24, 48, 96, 240, 480, 720 or 1000 hours. The duration is determined by the customer specification or product standard.
Salt Spray Procedure
- 1Samples are cleaned, marked and edges masked if necessary.
- 2Chamber conditions (temperature, solution, flow rate) are verified.
- 3Samples are placed on the rack at the defined angle.
- 4Continuous fog is applied for the specified period of time; Observations are recorded at intermediate control points.
- 5At the end of the exposure, samples are washed, dried and evaluated.
Salt Spray Acceptance Criteria
Acceptance criteria are defined in the product standard or customer specification, not in the test itself. Common criteria: no red rust after a certain period of time, no corrosion spread beyond the specified millimeter around the scratch.
Evaluation of Results
Evaluation is made by visual inspection and grading of defects such as blistering, rust, and scratch propagation. The results are comparative; Results obtained in different cabins cannot be matched exactly.
Salt Spray Report
- Applied standard and revision year
- Chamber conditions and verification records
- Exposure time and interim control observations
- Sample description and photographs
- Assessment result
Accreditation
EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.
Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.
Scope and authorisationsRelated Regulations
- Product based specifications
- Automotive OEM standards (VDA, SAE)
Corrosion Tests — What Does This Testing Field Cover?
The section below describes the field that the Salt Spray test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.
Corrosion testing assesses under accelerated conditions how long metals and coatings last in a corrosive environment. The family contains two approaches, and the difference between them is the most important knowledge in the field: constant-condition tests and cyclic tests.
Constant-condition salt spray (ASTM B117, ISO 9227) maintains the same environment in the chamber throughout: the same salt concentration, the same temperature, a continuously wet surface. The strength of this approach is its REPEATABILITY; because the conditions are tightly defined, results from different laboratories come out close to one another. That is exactly the property wanted when monitoring production consistency and comparing suppliers.
But the real atmosphere is not constant. A surface gets wet, dries, warms, cools, takes UV and becomes soiled. The wet-dry cycle changes the corrosion mechanism: during drying the salt concentrates, oxygen access increases and corrosion accelerates. The form of damage on a continuously wet surface differs from that on a cyclically wetted one.
Cyclic tests (SAE J2334, VDA 233-102, ASTM G85, ISO 16701) imitate this variability and give results closer to the damage patterns seen in the field. The automotive sector has largely moved to this approach. The practical consequence is this: the same two coatings may RANK DIFFERENTLY in constant and cyclic tests; which test was applied determines the result.
No test in this family defines a DURATION OR ACCEPTANCE CRITERION. How many hours it is applied for and what level of damage is acceptable come from the product standard or the customer specification. The assessment scales are defined in separate standards: different scales are used for degree of rusting, blistering, creep from a scribe and loss of adhesion.
The damage looked for varies with the coating type. For metallic coatings, white rust (corrosion of the coating itself) and red rust (corrosion reaching the base metal) are reported separately, and specifications usually give a separate duration for each. On painted surfaces, creep from a scribe and blistering come to the fore.
Electrochemical methods are a separate body of work and answer a different question. Potentiodynamic polarisation, electrochemical impedance spectroscopy and pitting potential measurements reveal the MECHANISM and rate of corrosion within hours; chamber tests give the result visually over weeks. The two are complementary rather than alternatives.
Stainless steels have a special sub-body in the field: pitting and crevice corrosion and intergranular corrosion tests indicate the quality of the heat treatment and the condition after welding.
Method groups in this field
Constant-condition salt spray
ASTM B117 and ISO 9227 (NSS); for repeatable comparison and process control.
Acidified and accelerated
The AASS and CASS conditions of ISO 9227; preferred for decorative chromium-nickel coatings.
Cyclic corrosion
SAE J2334, VDA 233-102, ASTM G85 and ISO 16701; approaches field behaviour through wet-dry cycles.
Humidity and condensation
Steady damp heat, condensation and cyclic humidity tests; these reveal coating blistering.
Electrochemical
Polarisation, impedance spectroscopy, pitting and crevice corrosion potential measurements.
Stainless steel specific tests
Pitting and crevice corrosion, intergranular corrosion; indicators of heat treatment and weld quality.
Assessment scales
Scales for degree of rusting, blistering, creep from a scribe and loss of adhesion; the ratings come from these standards.
Commonly confused in this field
- Chamber hours cannot be converted into field life; there is no reliable conversion factor.
- Constant and cyclic tests can produce different rankings; whichever the specification states is the one applied.
- A corrosion report without a stated duration and acceptance criterion cannot be interpreted.
- If the coating thickness is not reported, the result cannot be compared; thickness directly affects durability.
- White rust and red rust say different things; the two must be reported separately.
- The position and angle of the specimen in the chamber affect the result; standards govern this and the report must document it.
Which decisions these results support
- Selection of the coating system and supplier approval
- Process control of the coating line and lot acceptance
- Evidence of durability for automotive and outdoor products
- Assessment of field corrosion damage and warranty decisions
- Verification of heat treatment and weld quality in stainless steel
Related Tests
Frequently Asked Questions About Salt Spray
What is the difference between ASTM B117 and ISO 9227?
They both describe a neutral salt fog experiment, and the conditions largely overlap. Differences are in solution preparation, pH range, sample placement, and reporting details. Which standard will be applied is determined by the product specification.
Does the salt mist test give the real lifespan of the product?
It doesn't. The test is an accelerated comparative experiment; There is no direct conversion factor with field life. For real environmental behavior, cyclic corrosion tests give more representative results.
How many samples should I send?
Generally, at least three samples are recommended. The exact quantity depends on the standard to be applied and the evaluation method in your specification; It is notified in writing at the offer stage.