Corrosion Systems, Services, and Supplies

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.

The salt spray test (ASTM B117, ISO 9227) exposes materials to a controlled salt fog. It is the most widely recognized accelerated corrosion test.

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.

Automotive, aerospace, marine, military, coatings, and industrial labs rely on salt fog chambers for corrosion durability testing.

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. It is intentionally structured to allow flexibility in application while driving consistent environmental conditions and verification measures. The practice of ASTM B117 focuses on verifying that the fog environment is properly generated and uniformly distributed across the exposure zone through measured collection performance and controlled operating parameters.

Fog collection and placement are addressed in Section 10.2 and Section 7 governs specimen positioning. Taken together, these sections establish that:

• collectors must be located within the exposure zone and positioned relative to the atomizers and test specimens to verify fog distribution
• specimens must be positioned to ensure free and unencumbered exposure

This wording of collector placement does NOT define the exposure zone testing space for sample placement.

Section 10.2 of ASTM B117 uses non-mandatory, guidance-type language (for example, “a typical arrangement is shown in Fig. 1”) and does not prescribe exact geometric relationships between collectors and specimens, nor does it prohibit specimens from being located between a collector and an atomizer tower. The longstanding intent of the ASTM G01 task group has been to ensure accurate verification of the fog environment rather than to mandate a single cabinet loading geometry.

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.

Organizations that are NADCAP accredited, on the other hand, have agreed to operate within the NADCAP process control framework and should follow applicable NADCAP auditor guidance as part of maintaining their accreditation status. Where NADCAP establishes additional interpretive expectations, these should be understood as NADCAP program requirements rather than prescriptive mandates contained within ASTM B117 itself.

We encourage all users of ASTM B117 to participate in the ASTM standards development process and, where clarification of NADCAP-specific expectations is desired, to engage through the appropriate NADCAP Task Group channels so that continued alignment between industry practice and the published standard can be achieved. The ASTM G01.05.03 committee is currently in the process of revising ASTM B117 to clarify that the NADCAP interpretation reflects a program-specific expectation rather than the original intent of the ASTM B117 practice.