The monitoring and control of corrosive gaseous contaminants has been a long-time requirement in process industries such as pulp and paper manufacturing, petroleum refining, chemical manufacturing, mining and metals. Other applications such as semiconductor fabrication, electronics manufacturing, and wastewater treatment have also identified the need to monitor and control corrosive contaminants to extremely low levels to prevent destructive effects on materials, and to provide for continuous, safe, and profitable operation.

This article focuses on reactivity monitoring that directly measures the growth of corrosion on prepared copper and silver sensors. This method provides an excellent indication of the types and levels of corrosive chemicals present in the environment.

Passive Corrosion Monitoring

Purafil produces both passive and real-time reactivity monitors and each can be used to gather important information on gaseous pollutants in the environment. A passive air monitoring program using Purafil’s Corrosion Classification Coupons (CCCs) offers an inexpensive air quality indicator.

Purafil’s CCCs are passive monitoring devices exposed to the environment for a period of 30-90 days and then analyzed for the amount and type of corrosion which has formed. Figure 1 This can provide reactivity rates, and the types and relative levels of corrosive pollutants. While CCCs are good for measuring average corrosion rates, they do not allow for the measurement of any variations in the number, types, and amounts of contaminants that may have occurred during the monitoring period. It is possible that all of the corrosion occurred on one day when there may have been a chemical spill or other upset condition as often happens during normal manufacturing operations.

Real-Time Corrosion Monitoring

The long-term collection of corrosion rates is the most effective in predicting failures that would ultimately impact electronic equipment reliability. Purafil’s development of a real-time corrosion monitor capable of providing this information along with corresponding temperature and relative humidity served to eliminate the limitations associated with passive reactivity monitoring.

Purafil revolutionized reactivity monitoring through the development of a patented, real-time monitor employing metal-plated quartz crystal microbalances. Figure 2

The OnGuard™ 4000 Atmospheric Corrosion Monitor Figure 3 is designed to measure the total environmental corrosion caused by gaseous pollutants. The OG4 can detect and record changes of <1 ppb of targeted corrosive gases. The OG4 monitors corrosion on a continuous basis that allows for preventive action to be taken before serious damage has occurred. Custom alarm levels can be set for each unique application.

An internal data logger stores the results to be accessed through the internet or directly transmitted to a process control system, providing easy access to data and graphs. The OG4 also features a direct interface through the integrated backlit LCD and keypad.

When incorporated into a facility’s preventive maintenance program, it can help identify and reduce the number of corrosion-related failures with the ultimate goal being to eliminate production downtime.

Employed in either real-time or passive form, Purafil’s reactivity monitoring technology is being used as a method of gauging contaminant levels and to evaluate the effectiveness of contamination control strategies.


Real-time corrosion monitoring is typically used to prevent corrosion, but it can also be used as a troubleshooting tool. Purafil recently worked with two data centers – one needed to find the source of an issue (DC1) and the other to prevent corrosion (DC2).

To troubleshoot an existing issue, DC1 used two OG4s. One unit was placed in the area where cool air is pushed into the servers and the other unit was placed in the space where the warm air is pushed out. By placing the OG4s in the two areas, the team was able to pinpoint a problem with their filters and  found an easy solution using Purafil’s PuraFilters. Learn more about Purafil Filters

DC2 and most data centers use real-time corrosion monitoring to prevent corrosion. DC2 is located near two airports, so protecting against jet fuel exhaust is imperative to prevent costly downtime. DC2 placed OG4s in their facility so they can detect corrosion before their equipment starts malfunctioning.

Need to overcome corrosion issues in your environment?

Learn more about Purafil’s monitoring solutions

Article contributed by Chris Muller


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