Which sensors monitor corrosion rates in process lines?

• A. Thermocouples
• B. Pressure transmitters
• C. Corrosion coupons and ER probes
• D. Flow meters

Answer: (C)

Measuring how fast metal in a pipe or line is deteriorating requires devices that respond to actual corrosion, not just related signals. Corrosion coupons and ER probes do exactly that. A corrosion coupon is a small piece of the same material as the line that sits in the flow; after a set exposure, it’s removed and weighed to determine how much material was lost, giving a direct corrosion rate over that period (often reported as mils per year or mm/year). An ER (electrical resistance) probe is installed in the line and continuously monitors changes in the metal’s electrical resistance as it corrodes; the change translates into a real-time corrosion rate. These methods provide quantitative insight into how aggressively the environment is attacking the metal, which is essential for corrosion management and preventive actions.

Thermocouples only measure temperature, not corrosion. Pressure transmitters measure pressure, and flow meters track how much fluid is moving. None of those primarily quantify how quickly the metal is corroding, which is why corrosion coupons and ER probes are the best fit for monitoring corrosion rates.