PIPEVUE Corrosion Monitoring Plugs detect internal pipe corrosion in hydronic systems so maintenance can be performed before the system fails. PIPEVUE Corrosion Monitoring Plugs are manufactured from mild carbon steel and it's surface corrodes as the pipe corrodes. When the monitor corrodes beyond its limit (0.040") moisture penetrates the sealed chamber and transforms the brilliant white sight glass to a flourescent orange color indicating a corrosion problem in the piping system.