The Impact of Humidity and Wet/Dry Transitions in Salt Spray Corrosion Testing

Q-Lab's Senior Technical Marketing Specialist and Calibration Technical Manager Bill Tobin recently presented a webinar highlighting Relative Humidity and Wet/Dry Transitions in Salt Spray Corrosion Testing. Here are some of the key takeaways from the presentation:

An Introduction to Salt Spray Corrosion Testing

Salt spray corrosion testing plays a crucial role in the automotive industry, helping manufacturers assess how materials endure harsh environmental conditions over time. The webinar discusses how modern automotive corrosion test methods have added an emphasis on relative humidity and wet/dry transitions  . 

The Role of Humidity in Salt Spray Corrosion Testing

One of the key points made throughout the webinar was the influence of relative humidity on salt spray corrosion testing. Different salts, such as sodium chloride and calcium chloride, affect the corrosion process in unique ways due to their varying moisture absorption characteristics (deliquescence). Understanding how the changes in temperature and humidity impact corrosion rates is essential for those wanting to conduct accurate automotive corrosion testing, simulating real-world conditions in testing environments.

Variability in Test Results and the Need for Standardization

A significant challenge in accelerated corrosion testing is the variability in results when running automotive standards. Different laboratories or even changes in laboratory environments can produce inconsistent outcomes while meeting standards as-written. This is why it is crucial for modern methods to provide more specific controls for better reproducibility. The transition between wet and dry conditions during a salt spray test plays a critical role in ensuring repeatable and accurate results.

Case Studies in Corrosion Variability

Two examples demonstrate issues with variability when running standards. In the first case, ASTM G85 Annex 5 was run on two different testers in the same laboratory, and the results were very different. Since that standard doesn’t specify how to transition from wet to dry, a tester with a slower transition will create a more severe corrosion environment. The second case was about an OEM standard that modifies SAE J2334, a more modern test with specific RH conditions. In this case, two different laboratories were getting very different results. It was found that one laboratory was drying the chamber quickly after salt spray, which reduced the overall corrosion rate. With that information, Q-Lab was able to recommend an adjustment to Q FOG CRH programming to to simulate this fast dry off and achieve the same conditions.

In both cases, the standard did not provide strict instructions on the transition between steps, which led to a large amount of variability between labs running the test.
 

Addressing Variability with the Q-FOG CRH 

To better control wet/dry transitions, Q-Lab encourages customers running modern corrosion tests to use the Q-FOG CRH , which offers precise control over humidity during salt spray corrosion testing. This modern technology allows for controlled, linear transitions in humidity, ensuring consistent performance between laboratories or with changing laboratory environments.

Conclusion: Achieving Consistency in Accelerated Corrosion Testing

nderstanding how factors like relative humidity and transition times impact salt spray corrosion testing is essential for manufacturers. By using modern standards that specify relative humidity transitions, and using corrosion chambers with precise humidity control like the Q-FOG CRH, companies can ensure their products meet the highest performance and safety standards. Accurate and consistent accelerated corrosion testing is crucial for developing durable automotive components that can withstand real-world exposure and last longer in demanding conditions.

Interested in similar content? Head to www.Q-Lab.com/Webinars to access a full library of previously recorded webinars on a variety of weathering and corrosion topics.