Ultrasonic Thickness Gauge
One of the most common methods of measuring steel plate thickness is an ultrasonic thickness gauge. These gauges can be used while performing a bridge inspection to determine changes in steel plate thickness between inspections. These are also used to confirm the actual thickness of a nominally specified plate.
This only shows corrosion changes between inspections. It doesn't continuously monitor corrosion.
Continuous monitoring of steel corrosion is an interesting topic of research for strands of suspension bridges. There are a lot of methods that have been researched, these mostly rely on detecting minor changes in electrical, magnetic, or acoustic changes in the steel strands. The types studied are:
- Linear polarization resistance (LPR) sensors.
- Coupled multiple array sensors (CMASs).
- Bimetallic (BM) or galvanic sensors.
- Temperature-relative humidity sensors.
- Acoustic emission (AE).
- Magnetostrictive (MS).
- Main magnetic flux method (MMFM).
It is also useful to measure and detect any corrosion occurring in the reinforcing steel embedded in concrete. These types of monitors are useful to determine corrosion so that remediation measures can be planned before more visible damage has occurred. In concrete, this damage is usually in the form of spalled concrete.