There is extensive real-world reliability data, and it’s one of the strongest differentiators of our equipment.

Our chambers are used daily in our accredited corrosion lab, running harsh OEM cyclic tests like GMW 14872 and Ford L-467.

Many customers—including Toyota, Honda, Tesla, Magna, ZF, Denso, Valeo, Bosch, Boeing, and numerous Tier-1 suppliers—run our chambers 24/7.

A significant portion of our installed base has been in service 15–25 years with only routine PM. Legacy Harshaw units from the ’80s and ’90s still operate after simple refurbishment.

In the context of ASTM B117, the terms are interchangeable and refer to the same continuous spray environment.

ASTM B117 defines the equipment, solution, temperature, and exposure conditions for valid corrosion testing.

ASTM B117 does not specify relative humidity directly. Instead, the standard controls the chamber environment through cabinet temperature, atomizing air conditioning, and controlled salt fog generation.

In most salt spray chambers, humidity can be estimated using a combination of wet bulb temperature and the chamber air temperature. These values allow laboratories to calculate approximate relative humidity during testing.

Auto Technology chambers include a wet bulb thermometer and exposed RTD temperature measurement, allowing operators to monitor chamber conditions and estimate humidity while maintaining the controlled fog environment required by ASTM B117.

You should still follow Section 8.2. A pH meter's automatic temperature compensation feature does not change the temperature requirements of ASTM B117.

Temperature compensation is commonly misunderstood. The feature compensates for the difference between the temperature at which the meter was calibrated using pH buffers and the temperature of the sample being measured. It is not technically temperature-correcting the chemistry of the sample itself.

For example, if a meter is calibrated with pH buffers at 25 °C, it can accurately apply that calibration to a sample measured at a different temperature. Without this feature, the pH buffers and sample would need to be brought to the same temperature to ensure an accurate measurement.

Accordingly, users should continue to follow the pH measurement requirements specified in ASTM B117 Section 8.2.

You need to confirm what temperature the hydrometer was calibrated at. If it was calibrated at 60 °F (15.6 °C), standard correction tables can be used to adjust the observed specific gravity reading when measurements are taken at another temperature.

For example, a hydrometer calibrated at 60 °F with a measured specific gravity of 1.000 taken at 77 °F (25 °C) would require a correction of +0.0018, resulting in a corrected specific gravity of 1.0018.

If the hydrometer was calibrated at a different temperature, a different correction table or calculation may be required. Always verify the calibration temperature before applying correction factors.

Typical exposures range from 24–96 hours for coatings screening to more than 1,000 hours for qualification work.

Section 8 of ASTM B117 states that the salt solution shall be prepared as "...5 ± 1 parts by mass of sodium chloride in 95 parts of water..." This requirement is operationalized in Table 1, where Footnote B states that the acceptable solution concentration should be validated by measurement at 25 °C, with an allowable range of 4.0% to 6.0%. The sodium chloride to water ratio and the 4% to 6% range represent the control limits of the practice.

The language referenced in Appendix X1.4, along with Note 10, are informational observations that salt solutions ranging from 2 % to 6 % have been shown to produce similar behavior. They are included to provide information; not to redefine acceptable operating limits. They do not supersede the mandatory requirements in Section 8 and Table 1.

From a compliance standpoint: a salt solution measured below 4.0 % at 25 °C would fall outside the specified operating limits of ASTM B117.

It's important to remember that ASTM B117 is a standard practice, not a material or coating performance specification. Its primary objective is repeatability and consistency of exposure conditions, rather than defining corrosion performance outcomes. ASTM B117 has always acknowledged that perfect uniformity across all laboratories is unattainable, which is why the standard includes flexibility, tolerances, and informational commentary.

ASTM B117 is defined as a Standard Practice for Operating a Salt Spray Apparatus. It is not a coating performance specification. B117 is intended to produce a controlled, repeatable salt fog exposure across a wide range of specimen types, including flat panels, fasteners, and complex geometries. Notably, the non-mandatory appendix explicitly addresses flat test panels, specifying a 30° orientation from vertical.

ASTM B117 differs from coating performance standards in that it establishes a standardized exposure practice while retaining broader orientation allowances to maintain uniformity across diverse specimen geometries. In contrast, coating standards and AMS specifications are material performance specifications. They typically involve flat test panels allowing for tighter specimen angles.

Obviously, the shift from 6° to 15–30° from vertical results in changes in runoff behavior and wetness that can significantly alter corrosion mechanisms. In some cases, the tighter orientations specified in coating standards may intentionally limit sustained wetness to avoid overstressing coatings. The origins and implications of these differing approaches probably warrants a study.

It is also worth noting that positioning specimens outside specified angles would not align with practice or specification requirements.

Note 4 is an informational note describing how dissolved carbon dioxide in water used to prepare the salt solution can influence pH after the solution is atomized. It does not introduce a superseding requirement to Section 8.2, and it is NOT intended to suggest that the user heat the collection solution and allow to cool immediately before measuring the pH.

The language of Note 4 repeatedly refers to the “solution prepared from water saturated with carbon dioxide at room temperature” and to pH adjustment during solution preparation. The three methods described in Note 4 are presented as alternative approaches for managing a CO₂-related pH shift prior to atomization, so that the atomized and collected solution at 35 °C fall within the specified pH limits.

Section 8.2 defines the required salt solution chemistry and references Note 4 for informational purposes. Section 10.2, when addressing atomization and pH measurement of the collected solution, simply refers back to the solution requirements established in Section 8.2 and the explanatory guidance provided in Note 4.

It's important to remember that ASTM B117 is a standard practice, not a material or coating performance specification. Its primary objective is repeatability and consistency of exposure conditions, rather than defining corrosion performance outcomes. ASTM B117 has always acknowledged that perfect uniformity across all laboratories is unattainable, which is why the standard includes flexibility, tolerances, and informational commentary.

As outlined in Section 3.1, ASTM B117 is a standard practice focused on providing a controlled corrosive environment for “specimens of metals and coated metals exposed in a given test chamber.” ASTM B117 is not a performance specification with explicit geometric instructions for every aspect of salt fog cabinet loading.

The NADCAP Auditor’s Handbook promotes a more prescriptive expectation that “a collector shall be placed closer to each atomizer tower than any test pieces.” This represents a NADCAP program interpretation intended to drive additional uniformity within accredited aerospace laboratories. However, this specific geometric requirement is not a stated requirement, nor is it supported by the ASTM G01 technical committee, and it does not appear in the text of ASTM B117 as mandatory language within the practice.

Accordingly, organizations not operating under NADCAP accreditation are not subject to this NADCAP-specific interpretation when claiming conformance to ASTM B117, provided all required environmental controls and verification criteria of the standard are satisfied.