What Is Humidity Cabinet?
The humidity chamber test is one in which the sample is held under high relative humidity or direct condensation conditions and assessed for blistering, loss of adhesion and corrosion.
Purpose of Humidity Cabinet
The purpose is to verify that the coating system maintains adhesion to the surface under continuous moisture and that no blistering occurs.
Which Products Is Humidity Cabinet Applied To?
- Paint and varnish systems
- Powder-coated surfaces
- Coated sheet metal parts
- Building components
In Which Sectors Is Humidity Cabinet Used?
Standards Related to Humidity Cabinet
- ISO 6270-1strength in condensation environment test
- ISO 6270-2strength in condensation environment test
- ASTM D2247
- ASTM D4585
- ASTM B117tuz sisi (salt spray) korozyon testi test
- ISO 9227tuz sisi korozyon testi test
- ASTM G85modified salt fog (cyclic) test test
- ASTM G48pitting and crevice corrosion in stainless steels test
- ISO 16701cyclic corrosion test test
- ISO 6270strength in condensation environment test
- SAE J2334cyclic laboratory corrosion testing test
- VDA 233-102cyclic corrosion testing in automotive test
Humidity Cabinet Conditions
- Relative humidity
- Defined in the standard; In the condensing method, a continuous water film is formed on the surface
- Temperature
- Defined in the standard; typically on the order of 40 °C
- Method
- Constant condensation or controlled high humidity
- Time
- Duration in hours defined in the specification
Equipment for Humidity Cabinet
- Humidity/condensation chamber
- Temperature and humidity control system
- Pure water supply system
- Thickness and adhesion measurement instruments
Sample Requirements for Humidity Cabinet
- Generally at least three specimens
- The coating must have fully cured
- Dry film thickness must be recorded
- Edges must be masked
Duration of Humidity Cabinet
Typically in the range of 240 – 1000 hours depending on the specification.
Humidity Cabinet Procedure
- 1Coating thickness and initial condition are recorded.
- 2Chamber temperature and humidity conditions are verified.
- 3Samples are placed at the defined position.
- 4Conditions are maintained for the defined duration.
- 5At the end of the exposure, blistering, colour change and adhesion are assessed.
Humidity Cabinet Acceptance Criteria
The acceptance criterion is given in the specification as blistering grade, colour-change limit, or minimum post-test adhesion strength.
Evaluation of Results
Blister size and density are assessed per the standard's grading scale. A post-test adhesion test is usually required alongside.
Humidity Cabinet Report
- Standard and method applied
- Temperature, humidity and duration
- Coating system and thickness
- Blistering grade and adhesion result
- Photographs
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
- Paint and coating product specifications
Corrosion Tests — What Does This Testing Field Cover?
The section below describes the field that the Humidity Cabinet 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 Humidity Cabinet
According to which standard is Humidity Cabinet made?
Humidity Cabinet is executed in scope ISO 6270-1, ISO 6270-2, ASTM D2247 and ASTM D4585. The limit values and acceptance criteria to be applied are defined in the product standard; The version valid for your product is confirmed in writing at the offer stage.
Which products does Humidity Cabinet apply to?
Mainly applied to Paint and varnish systems, Powder-coated surfaces, Coated sheet metal parts and Building components. Whether your product is included in the scope is determined by examining its technical specifications and intended use.
Under what conditions is Humidity Cabinet done?
The determining parameters are: Relative humidity — Defined in the standard; In the condensing method, a continuous water film is formed on the surface, Temperature — Defined in the standard; typically on the order of 40 °C and Method — Constant condensation or controlled high humidity. The full terms are in the "Test Conditions" section on the page and vary depending on the product standard.
What kind of sample is needed for Humidity Cabinet?
Generally at least three specimens, The coating must have fully cured and Dry film thickness must be recorded. The number of samples is determined according to the product standard and the scope to be reported.
How long does Humidity Cabinet take?
Typically in the range of 240 – 1000 hours depending on the specification. This duration belongs to the experiment itself; sample preparation, queuing and reporting are also evaluated. A realistic schedule for your product is given in the offer.
What is the Humidity Cabinet result called "appropriate"?
The acceptance criterion is given in the specification as blistering grade, colour-change limit, or minimum post-test adhesion strength.