Expired Medications as Corrosion Inhibitors

The objective of this study is to use expired medications as green corrosion inhibitors that can be used during stimulation treatments. Because the medications are expired and not fit for human consumption, the cost is inherently low.

capsules and drug tablets on orange background
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As environmental awareness is rising worldwide, the oil and gas industry is introducing alternative chemicals in its operations that can degrade after disposal. Yet, there is a bigger concern regarding waste materials that are generated daily and accumulate in landfills with minimal recycling solutions. Research has shown that flushed expired medications leach pharmaceuticals into the environment, consequently causing severe harm to plants and aquatic life. This paper explores the possibility of using expired high-use medications as corrosion inhibitors.

To determine the inhibition efficiency of expired medications, low-carbon steel metal coupons were exposed to 15 wt% HCl solutions at temperatures between 77 and 200°F. The medications have been divided into three categories based on their functionality: Category A, Category B, and Category C. Medications from each category were powdered and were used in these tests at a concentration of 2 wt% for 6 hours. In addition, a control solution containing no corrosion inhibitor was used to establish a corrosion rate for a base case.

Category C medication was observed to perform well at room temperature, providing a maximum of 99% corrosion inhibition efficiency. Category A and Category B, on the other hand, did not provide as much corrosion inhibition. At a temperature of 150°F, the control solution showed a catastrophic failure producing a corrosion rate of 0.371 lbm/ft2, whereas the use of Category C medication was observed to maintain good corrosion inhibition efficiency of 88.3%. When the temperature was raised to 200°F, the corrosion rate observed was 0. 0.0352 lbm/ft2 for Category C medication, in the presence of 1 wt% corrosion inhibitor intensifier. These results pass the oil and gas acceptable low-carbon steel corrosion requirements of producing a corrosion rate below 0.05 lbm/ft2 for 6 hours.

This work shows that expired medications can be used as corrosion inhibitors. Because they are expired and not fit for human consumption, the cost is inherently low. Thus, these chemicals may provide alternatives to commercial corrosion inhibitors while concurrently reducing damage to the environment.

SPE members can download the complete paper from SPE’s Health, Safety, Environment, and Sustainability Technical Discipline page for free from 20 June to 3 July.

Find paper SPE 216036 on OnePetro here.