Introduction to Corrosion Coupons

Corrosion coupons are commonly used in the water treatment and oil & gas industries to monitor internal corrosion inside closed systems. Coupons are used to monitor pipelines, heat exchangers, cooling towers, injection molds and many other applications. Coupons can be made in the form of flat strips, discs, and rods depending on the application.

Coupons should be made from materials similar to those used in the system. The most common materials are carbon steel and copper, but we provide coupons made from more than 150 different materials, including API-grade pipe, Admiralty brass, nickel superalloys and a wide range of exotic materials. Many of these materials are only available as flat bar, round bar, plate, or pipe, so we have extensive machining capabilities to transform any raw material into a corrosion coupon.

Once the coupons have been produced, they are marked with a unique serial number for identification and traceability. Coupons must have a consistent finish, free of defects to supply reliable data. This finish can be applied through blasting, grinding, machining and many forms of polishing.  After finishing coupons should only be handled with nitrile or latex gloves and be protected from the environment to prevent premature corrosion or oxidation.

The final and most critical step in the production process is to weigh the coupon on an analytical balance to 4 decimal places.  The balance should be calibrated and validated frequently to ensure accurate weights.

Coupons are installed on a coupon holder where they will be exposed to the fluid inside the system. Standard exposure is 90 days, but this can be reduced or extended depending on the level of corrosion found in the system. 

After exposure, the coupons will be sent back to a laboratory where they are cleaned and re-weighed. Based upon the weight loss and exposure time a corrosion rate can be calculated in mils per year. This formula and additional information on corrosion coupons can be found on our coupon analysis page and is published in industry standards such as ASTM G1 and NACE SP0775. We perform post-exposure analysis for many of our coupon customers.

Pacific Sensor can manufacture corrosion coupons to meet your specification from any commercially available material. See our alloy table for information on materials we have worked with in the past. If the material you need is not listed, please contact us. We list a few common coupon sizes and materials in our online store, but we offer more than 10,000 different coupons, so please contact us for a quote.