Is Bubble Tower Temperature Calibration in Corrosion Testing Really Necessary?

The short answer to this question is no, for two main reasons:

1. There are no international corrosion standards that contain mandatory requirements for the bubble tower water temperature.
2. Bubble tower temperature is not critical to testing, and as a result, international corrosion test standards do not require bubble tower thermometer calibrations. 

The salt fog test standard ASTM B117, published in 1939, called for “saturation towers,” now known as “bubble towers,” to promote repeatability. However, by 1954 scientists and engineers understood that bubble towers were not a critical part of the test, and the standard language in ASTM B117 and its analog ISO 9227 has changed over time to clarify that the bubble tower temperatures and compressed air pressures are non-mandatory. The test setup only requires that salt spray collections meet all specifications in terms of rate, pH, and concentration. In fact, the latest version of ISO 9227 removed the requirement to have a bubble tower to run the test!

Bubble tower temperature is best understood as a tool to help meet the collection rates required in corrosion test standards. As an additional benefit, a bubble tower cleans incoming compressed air. However, bubble tower temperature does not require calibration or precise temperature control, since the software in the Q-FOG accelerated corrosion tester independently achieves excellent temperature control inside the chamber and accurate control of salt spray collection rates.

Although bubble tower temperatures are not mandated in standards, they can be both calibrated (compared to a reference value) and adjusted. However, Q-Lab strongly advocates keeping tests as simple as possible. Since Q-Lab and corrosion experts agree that other technical features and parameters in accelerated corrosion testing are far more important, Q-Lab’s view is that calibrating bubble tower temperature or pressure of atomizing air is an unnecessary use of resources.