ConstaTwin® TR – Chest-Type Salt Spray and Condensation Humidity Test Chamber

ConstaTwin® TR is a combined corrosion test chamber developed to perform salt spray and condensation humidity tests within the same chest-type chamber.

The chamber combines the S salt spray system of the ConstaSal series with the K condensation humidity system of the ConstaCon series. This enables both standard salt spray and condensation humidity tests to be performed without requiring laboratory space for two separate chambers.

On the ConstaTwin M-TR, the process to be used is selected by the operator. The chamber operates in either salt spray or condensation humidity mode. It does not create a fully automatic programmed cycle between the two processes. The chamber is therefore suitable for laboratories that perform salt spray and humidity tests at different times.

ConstaTwin TR was developed for users who perform both salt spray and condensation humidity tests in the same laboratory but do not need these processes to run automatically in sequence within a single test programme.

The chamber can be used to perform salt spray and condensation humidity resistance tests on:

• Paints and organic coatings,
• Metals and metal alloys,
• Galvanised surfaces,
• Metallic and conversion coatings,
• Automotive and automotive supplier components,
• Large machinery components,
• Building and exterior façade elements,
• Wide, heavy, or bulky samples.

After testing, effects such as red rust, white corrosion, blistering, coating delamination, loss of adhesion, colour change, and corrosion progression around a scribe can be evaluated according to the relevant product standard.

ConstaTwin TR incorporates two different corrosion test processes:

• S system: Creates a salt fog atmosphere by spraying the salt solution under controlled conditions.
• K system: Creates a condensation humidity atmosphere by heating the demineralised water at the bottom of the test chamber.

The operator selects either salt spray or condensation humidity mode according to the test to be performed. Each process has its own temperature control and water supply arrangement.

Having both processes in the same chamber does not mean that they run automatically in sequence. When changing from one test type to the other:

• The current test is completed.
• The test atmosphere is safely exhausted.
• The chamber and relevant components are cleaned.
• The test solution and water systems are checked.
• The operator selects the new process mode.
• The temperature and operating parameters for the new test are set.

If regular, automatic cycling between processes is required, programmable ConstaMatic models should be selected.

In salt spray mode, the prepared test solution is transferred to the precision twin-fluid spray nozzle by a digital dosing system.

The test solution is atomised with conditioned compressed air to create a uniform salt fog inside the chamber.

Before testing, the operator sets the following according to the relevant standard:

• Test chamber temperature,
• Humidifying tower temperature,
• Spray air pressure,
• Test solution dosing rate.

During testing, the fog distribution inside the chamber and the amount of collected solution should be checked using collection vessels.

NSS is the most widely used continuous salt spray test method. A sodium chloride solution prepared within a neutral pH range is atomised using compressed air to create a uniform salt fog inside the chamber.

The method is particularly used for:

• Metals and metal alloys,
• Painted metal surfaces,
• Electroplated and metallic coatings,
• Conversion coatings,
• Anodised surfaces,
• Metal components with organic coatings.

Neutral salt spray testing forms the basis of many applications covered by ASTM B117 and TS EN ISO 9227.

In the AASS method, the salt solution is acidified with acetic acid to create a more acidic test environment. It is particularly used to evaluate decorative metallic coatings, anodic coatings on aluminium, and certain organic coating systems.

Before performing an AASS test, the chamber’s required temperature range and material compatibility should be assessed against the current requirements of the applicable standard.

CASS is a more aggressive salt spray method performed by adding a copper salt to an acidified salt solution. It is particularly used for the quality control of decorative nickel–chromium and copper–nickel–chromium coatings.

As CASS applications may require a higher test temperature, the chamber may need to be configured with the high-temperature operating option for temperatures up to 70 °C. The chamber configuration should be determined at the ordering stage according to the applicable test standard.

In condensation humidity mode, the demineralised water at the bottom of the test chamber is heated. As the water evaporates, it creates approximately 100% relative humidity within the enclosed test volume.

When the surface temperature of the test samples is lower than the chamber atmosphere, water vapour condenses on the samples. This exposes them to continuously high humidity.

The K system is particularly suitable for:

• Constant condensation humidity tests,
• The CH atmosphere specified in TS EN ISO 6270-2,
• The former method known as DIN 50017 KK,
• Long-duration humidity resistance tests.

ConstaTwin M-TR does not include the B system for automatic ventilation. Test stages requiring ventilation, such as AHT, can therefore only be performed with manual intervention. A suitable ConstaMatic configuration should be selected for regular, automatic ventilation cycles.

For detailed information about Liebisch system codes and other process combinations, please visit the Liebisch Process Systems page.

ASTM B117 – Standard Practice for Operating Salt Spray (Fog) Apparatus
Specifies the apparatus, operating conditions, and procedures required to create and maintain a salt spray test environment.

ASTM B368 – Standard Test Method for Copper-Accelerated Acetic Acid-Salt Spray (Fog) Testing (CASS Test)
Specifies the operating conditions for copper-accelerated acetic acid salt spray testing.

TS EN ISO 9227 – Corrosion Tests in Artificial Atmospheres — Salt Spray Tests
Covers neutral salt spray (NSS), acetic acid salt spray (AASS), and copper-accelerated acetic acid salt spray (CASS) methods.

TS EN 13523-8 – Coil Coated Metals — Part 8: Resistance to Salt Spray (Fog)
Used to evaluate the resistance of coil-coated metal surfaces to a salt spray environment.

TS EN 60068-2-11 – Test Ka: Salt Mist
Defines a method for evaluating the resistance of electrical, electronic, and similar products to salt mist.

TS ISO 9022-4 – Optics and Photonics — Part 4: Salt Mist
Intended to evaluate the resistance of optical instruments and related components under saline atmospheric conditions.

JIS Z 2371 – Methods of Salt Spray Testing
The Japanese Industrial Standard for conducting salt spray tests.

MIL-STD-202, Method 101 – Salt Atmosphere (Corrosion)
Used to evaluate the corrosion resistance of electrical and electronic components under salt-laden atmospheric conditions.

MIL-STD-810, Method 509 – Salt Fog
A military environmental test method for evaluating the resistance of equipment and materials to the effects of salt fog.

TS EN ISO 6270-2 – Resistance to Humidity in a Condensation Water Atmosphere
Specifies the conditions for exposing coated test samples to constant or alternating condensation atmospheres inside a test chamber equipped with a heated water reservoir.

The K system of ConstaTwin M-TR is particularly suitable for the constant CH atmosphere. AHT stages requiring ventilation must be performed with operator intervention.

DIN 50017 – Testing in Condensation Water Atmospheres
A German standard historically used for condensation humidity testing. Today, most of these methods are covered by DIN EN ISO 6270-2.

DIN 50958
A test method for evaluating the behaviour of metals and coated surfaces in a condensation humidity atmosphere.

TS EN ISO 6270-1 – Single-Sided Condensation
Determines the resistance of coated test samples to humidity under single-sided condensation conditions.

Applying this method may require special sample positioning or optional equipment. Suitability should be assessed together with the sample geometry and support system.

Standards That May Require Optional Equipment

The Liebisch TR standards matrix indicates that the following tests can be performed using the SK system, subject to the use of optional equipment:

• GME 60205
• GME 60207
• GMI 60206

For these standards, the current revision, temperature conditions, solution composition, and required test equipment should be confirmed before ordering.

If any of the following standards are to be applied, chamber suitability should be verified with the manufacturer based on the current revision of the standard and the required process stages:

• FIAT 50180 Method A1/A2/A3
• FIAT 50184 Method B
• Volvo STD 423-0018

This is because these methods may include automatic ventilation, hot air, controlled relative humidity, drying, or rain spray stages in addition to salt spray or constant condensation humidity.

If the required processes exceed the capabilities of the SK system, a ConstaMatic model should be selected.

ConstaTwin TR can be configured with the following options:

The suitability of each option should be evaluated together with the chamber volume, applicable standard, and laboratory infrastructure.

If you need to perform both salt spray and condensation humidity tests in the same laboratory but conduct them at different times, ConstaTwin M-TR may be a suitable solution.

Share your intended test standard, test cycle, sample dimensions, and required capacity with us so we can assess the necessary process systems and a suitable chamber configuration together.

Contact us for assistance with selecting the appropriate Liebisch process system and chamber, and for a technical quotation.