Corrosion inhibitors for severe environments require test conditions that simulates the system pressures and temperatures in order to realistically challenge the effectiveness of the products.
Cormetrics uses 300 mL UNS N10276 (Hastelloy C) autoclaves, jacketed with electric heaters regulated by temperature controllers. The units can be pressurized to over 5500 kPa at temperatures up to 170°C. The units are stirred magnetically to impart sufficient agitation to perform valid electrochemical measurements.
The autoclaves hold a triangular array of electrodes; with a UNS N10276 reference and mild carbon steel working and counter electrodes. The electrochemical measurements are made using a Gamry potentiostat connected to several cells via a multiplexer.
The cells are purged and pressurized with a gas mixture blended according to the field acid gas content (H2S, CO2, methane or nitrogen). The cells are placed in the jacket heaters and brought to system temperature using the temperature controller. Corrosion rate (LPR) readings are made every 30 minutes for the period of the test, usually 96 hours. The working and counter electrodes are cleaned, weighed for weight loss corrosion rate and photographed for the final report.
The test protocol can be modified to consider partitioning of inhibitors, use of mushroom cap coupons for under deposit corrosion or the crevice electrode.