• Indirect heating of the test chamber through a water jacket or air space is recommended and must be used. Therefore, electric heating elements inside the internal chamber are not allowed.

• The Lid must have a smooth internal finish, with no structural elements on the inside. It should have an angle between 90 and 125 degrees and be made of a material hard enough to resist the salt crystals’ scratching, preventing scratches that could cause dripping onto the samples, increasing the localized saline concentration on the specimens (samples), which would lead to distortions in the test results.

• The atomization nozzle must produce a FOG and not droplets (peristaltic pumps), complying with the Venturi principle (ASTM B117); peristaltic pumps are not recommended. The distance of the atomization flow can be controlled through the pressure of the bubble tower. Droplets of solution are not acceptable during atomization.

ASTM, ISO, and JIS standards require the saline solution to be atomized indirectly over the samples. Therefore, it should never be atomized directly onto the samples. The FOG flow (atomization of the saline solution) must be evenly distributed from top to bottom (floor), and using a fog dispersion tower with a cone is recommended. Mist collection is crucial to reach optimal test results. Uniform and constant collection is required by ASTM, ISO, and JIS standards.

• Internal Chamber Dimension: The chamber must be such that the homogeneity and distribution conditions of the fog (spray) are met. Internal chambers smaller than 14.2 ft³ (0.4 m³) generate undesirable effects in fog (spray) distribution, temperature, turbulence presence, and shorter distances not allowed between the internal walls of the test chamber in relation to the atomization nozzles and between them and the samples. (ASTM B117).

• Positioning of Samples in the Test Chamber: The position of test samples in the salt fog chamber during testing must meet the following conditions:

1. The specimens must be supported or suspended with the surface of interest at an angle between 15° and 30° from the vertical. It is recommended specimen orientation in the chamber to be consistent to minimize variability.
2. The specimens (samples) must not touch each other or any metal.
3. Each specimen (sample) must be placed to allow unobstructed exposure to the fog.
4. The saline solution from one specimen must not drip onto any other specimen.
5. The positioning of the specimens (samples) can also be defined by agreement between the involved parties.

Recommended Positioning of ASTM B117 Coupons: To avoid dripping of corrosion products from one coupon onto another, preventing distortions in the results.

Recommended Positioning of ISO 9227 Coupons: To avoid dripping of corrosion products from one coupon onto another, preventing distortions in the results.

• Quality: Salt / Corrosive Agents / Water / Compressed Air: The control of these items is very important for the test results.

Salt (NaCl) quality specifications, purity limits / undesirable chemical element concentrations must be considered. Refer to ASTM B117, ISO 9227, JIS Z 2371, among others. Refer to our CORRO SALT.

Water must meet ASTM D1193 – Type IV specifications (Max. 5 µS/cm). Water deionizers are desirable to achieve the required water quality.

Compressed air: The compressed air supply for the bubble tower (saturator) must be free of grease, oil, and dirt before use, passing through filters. This air must be maintained at sufficient pressure at the base of the bubble tower (saturator) to meet working pressure requirements.