What are corrosion coupons?
A corrosion coupon rack is a simple corrosion monitoring device that uses corrosion coupons, which are strips of metal that match the metals in the system where they are installed. The initial weight of each coupon is carefully measured and logged. They are then installed in the corrosion coupon rack where system water is allowed to pass over the metals for between 90-100 days. After the test period expires, they are pulled out, sent to a lab, and weighed. The difference in weight will represent the level of corrosion in the system.
Why is a corrosion coupon rack needed?
Regular corrosion coupon analysis provides valuable feedback on the effectiveness of a water treatment program. When corrosion inhibitors are maintained at prescribed dosages one should expect corrosion results to meet or exceed industry standards.
Tips for installation and maximum performance.
Several factors should be kept in mind for performing an accurate test.
Placement is important. Placing the rack behind a heat source increases corrosion, whereas placing the rack after a cooling tower leads to lower corrosion rates.
Avoid cooling system tests in Spring and Fall, as a consistent flow is needed for the most accurate results.
Flow rate, direction, and spacing all impact the outcome of the study.
Any contamination to your system, such as leaks, oils on from touching the coupons with your hands, or other contributors will also bias your test results.
What do the results mean?
Boland provides a corrosion coupon report for each coupon. Reports classify the corrosion levels as poor, moderate, good, or excellent based on industry standards. Results can help determine if changes in system chemistry need to be made to prevent further corrosion.